Ketjen Black Research Articles

Performance improvement of aqueous zinc batteries by zinc oxide and Ketjen black co-modified glass fiber separators.

Rechargeable aqueous zinc-based batteries (AZBs) are intriguing candidates for next-generation energy storage batteries. However, the dendrites generated plagued their development during charging. To inhibit the dendrite generation, a novel modification method based on the separators was proposed in this study. The separators were co-modified by spraying sonicated Ketjen black (KB) and zinc oxide nanoparticles (ZnO) uniformly. The highly conductive KB homogenizes the anode interface's electric field. The deposited ions are deposited on ZnO preferentially rather than on the anode electrode, and the deposited particles can be refined. The ZnO in the uniform KB conductive network can provide sites for zinc deposition, and the by-products of the zinc anode electrode reduced. The Zn-symmetric cell with the modified separator (Zn//ZnO-KB//Zn) can cycle for 2218 h at 1 mA cm-2 stably (the unmodified Zn-symmetric cell (Zn//Zn) only can cycle for 206 h). With the modified separator, the impedance and polarization of Zn//MnO2 reduced, and the cell can charge/discharge 995 times at 0.3 A g-1. In conclusion, the electrochemical performance of AZBs can be improved effectively after separator modification by the synergistic effect of ZnO and KB.

Efficient electrocatalytic oxygen reduction reaction of thermally optimized carbon black supported zeolitic imidazolate framework nanocrystals under low-temperature.

Turning commercially available low-cost conducting carbon black materials into functional electrocatalytic electrode media using simple surface chemical modification is a highly attractive approach. This study reports on remarkably enhanced oxygen electrocatalytic activity of commercially available Ketjenblack (KB) by growing a non-precious cobalt metal-based zeolitic-imidazolate framework (ZIF-67) at room temperature in methanol solution followed by a mild thermolysis. The resulting Co@CoOx nanoparticle decorated nitrogen-doped KB derived from the optimized ZIF-67 : KB weight ratio of hybrid samples at 500-600 °C shows high performance for the oxygen reduction reaction (ORR) with impressive Eonset and E1/2 values of ∼0.90 and ∼0.83 V (vs. RHE), respectively in 0.1 M KOH electrolyte. Such ORR activity is comparable to, or better than many metal@metal-oxide-carbon based electrocatalysts synthesized under elevated carbothermal temperatures and using multicomponent/multistep chemical modification conditions. Therefore, a simple electrocatalyst design reported in this work is an efficient synthesis route that not only utilises earth-abundant carbon black but also comprises scalable room temperature synthesized ZIF-67 following mild thermolysis conditions under 600 °C.

A high-performance tellurium-sulfur cathode in carbonate-based electrolytes

The current technology of lithium-sulfur (Li-S) batteries is hindered by the sluggish kinetics and low utilization of sulfur (S) due to its electronic insulating nature. Herein, tellurium (Te) is introduced into S by forming TexSy solid solutions to reshape Li-S chemistry and facilitate the solid-state conversion of the cathode in carbonate-based electrolytes. Numerical calculations suggest a more delocalized charge-density difference around the Te atoms in Li16Te1S7 compared to site-equivalent S atoms in Li2S, thus enabling lower energy barriers throughout the Li migration pathway. Mesoporous carbon Ketjenblack (KB) is employed to confine TexSy materials via a melt diffusion method. By tuning the molar ratio of Te/S, it is found that the Te1S7/KB cathode delivers the highest reversible capacity of 1306.7 mAh g−1 at 0.1 A g−1 and maintains a capacity of 959.8 mAh g−1 after 400 cycles at 1 A g−1. Kinetics analysis reveals that the introduction of Te accelerates Li-ion diffusion and decreases reaction resistance during the charge/discharge process, thus enabling fast and reversible redox conversion. Moreover, the Te-containing solid electrolyte layer on the electrode surface is generated to prevent the loss of Te1S7 active materials. These encouraging findings suggest that the heteroatomic Te1S7/KB is a promising cathode to achieve long cycle life and high energy density for Li-S batteries.

Dyeing to Carry Charge: Commercial Phthalocyanine Dyes as Charge Carriers for Redox Flow Battery Applications

The development of inexpensive charge carriers with long-term stability is critical to increase the economic viability of redox flow batteries (RFBs). Herein, we compare the performance metrics of a series of synthesized or commercially available inexpensive phthalocyanine metal (PcM) charge carriers with varying metal- or ligand-based substitution patterns. All systems were charged–discharged as slurries in conjunction with a conductive heterogeneous carbon source, Ketjenblack (KB). The synthesized, peripherally substituted 1,4,8,11,15,18,22,25-octaethoxyphthalocyanine (EtOPc) metal complexes, OEtPcVO and OEtPcNi, were cycled with KB, and their performance metrics were compared to their commercially unsubstituted analogues, PcVO and PcNi. No significant advantages were found in using the synthesized versus commercial variants despite the increased solubility of the former. Expanding these electrochemical analyses to several commercial first-row variants (PcTiCl2, PcVO, PcMnCl, PcFe, PcCo, PcNi, and PcCu) as well as one heavy-metal analogue (PcPb) revealed that most of these were effective charge carriers for slurry-based PcM/KB RFB applications. Of these, PcCu proved to have the highest efficiencies, energy density (1.23 Wh/L), and stability (>99% capacity retention) of the series while also having the lowest cost by mass.

Sandwich-Structured MXene/Carbon Hybrid Support Decorated with Pt Nanoparticles for Oxygen Reduction Reaction

Carbon supports for cathodic catalysts in proton-exchange membrane fuel cells suffer from rapid corrosion and instability; therefore, alternative supports with a stable structure and a high electric conductivity are highly required. In this paper, a three-dimensional support hybridized by MXene and Ketjen Black is developed, in which Ketjen Black is sandwiched between MXene nanosheets (MCM). After decorating with Pt nanoparticles by a facile wet-chemical approach, a three-dimensional (3D) Pt/MCM catalyst is obtained. The intercalated Ketjen Black prevents the stacking of MXene nanosheets, thus increasing the specific surface area of the catalyst and exposing the active sites. The strong interaction between functionalized MXene nanosheets and Pt nanoparticles further enhances its intrinsic electrocatalytic activity. Pt/MCM demonstrated encouraging ORR activity with the half-wave potential and specific activity of 0.892 V and 0.377 mA·cm–2, respectively, surpassing the state-of-the-art Pt/C catalysts. Especially, Pt/MCM achieves ultrahigh durability with a 1 mV decrease in half-wave potential and a 1.73% decrease in mass activity after an accelerated durability test. Given the performance and structure–activity relationships of Pt/MCM, it holds great potential for various energy and catalysis-related applications.

A Hybrid of the Fe4N-Fe Heterojunction Supported on N-Doped Carbon Nanobelts and Ketjen Black Carbon as a Robust High-Performance Electrocatalyst.

Herein, an extremely simple l-alanine-assisted pyrolysis method was proposed for the construction of a novel hierarchically porous hybrid of Fe4N-Fe supported on N-doped carbon nanobelts and Ketjen black carbon (denoted as Fe4N-Fe@N-C/N-KB). It has been found that the participation of l-alanine in pyrolysis can dramatically increase the total pyridinic-N/graphitic-N content in Fe4N-Fe@N-C/N-KB, which is peculiarly conducive to the enhancement of ORR performance. The in-site formation of the Fe4N-Fe heterojunction via the thermal reduction and decomposition of Fe3N as well as the introduction of cheap KB can significantly improve the ORR performance. As a result, the activity, durability, and methanol tolerance of this hybrid are comprehensively better than those of commercial 20 wt % Pt/C, promising future applications in practical devices. Density functional theory calculations disclose that the highly improved ORR activity of Fe4N-Fe@N-C/N-KB also benefits from the favorable electron penetration and excellent electronic conductivity between the Fe4N nanoparticles and the N-incorporated carbon frameworks.

Enhancement from Anaerobic Digestion of Food Waste by Conductive Materials: Performance and Mechanism.

Conductive materials (CM) have recently attracted research interest in the anaerobic digestion of food waste to achieve reduction and resource utilization. Fe-metal organic frameworks (Fe-MOF) and Ketjen Black (KB), the conductive materials (CMs), were added for the enhancement of food waste digestion. This study therefore, is intended to fill in this knowledge gap and clarify the underlying mechanism of CM-promoted performance. Batch experiments revealed that the optimal additions of Fe-MOF and KB were 0.5 g·L-1 and 0.2 g·L-1, respectively. The biogas production increased by 27.50% and 29.45% compared with the blank group, and the removal efficiency of volatile solids (VS), total solids (TS), and chemical oxygen demand (COD) increased by 18.28%, 40.52%, and 15.31%. The lag period was shortened from 3.042 to 2.006 and 1.544 days, respectively. Mechanism studies revealed that Fe-MOF and KB were beneficial to food waste digestion, and the functional groups of Fe-MOF and KB increased the buffer capacity of the system to pH and ammonia nitrogen. The physicochemical properties of Fe-MOF and KB promote the activity of the electron transfer system (ETS); the ETS activity was about 2 times the 11.32 mg·(g·h)-1 of the blank group. Zeta potential and electrical conductivity were beneficial to the establishment of intermicrobial direct interspecies electron transfer (DIET).

Toward Elucidation of Li Pre-Doping Reactions between Si Electrodes and Li-Naphthalenide Solutions

Next-generation batteries using Li negative electrodes have been attracting much attention recently. They still have many tough problems to be challenged, such as instability of surface chemistry and anomalous deposition of Li. Therefore, Si is regarded as a promising alternative for Li because of its relatively stable surface chemistry. Simple substitution of Si for Li induces two issues: one is large irreversible capacity of Si electrodes, and the other is lack of Li source in itself because some of cathode materials of next-generation batteries cannot supply. However, Li pre-doping enables us to straighten out these issues. We have already reported that the Li pre-doped capacities by Li-naphthalenide (Li-NTL) solution depended on the solvent of the Li-NTL solution [1]. In this study, we analyzed the effect of Li concentration in Li-NTL solution on Li doped capacities and equilibrium potentials by evaluating the solvation structures around Li+ ions and pairing structure of the solvated Li+ ions with [NTL]・⁻ in Li-NTL solutions by IR and UV-vis spectra. The results allowed us to discuss on the mechanism of the lithiation of Si in Li-NTL pre-doping solution. Si electrodes were formed on Cu foil substrate with a NMP slurry containing Si powder, Ketjen Black, and polyimide binder in a mass ratio of 80: 5: 15. Li-NTL pre-doping solution was prepared with 2-methyltetrahydrofuran (MeTHF) as solvent, naphthalene fixed at 2.5 mmol, and Li of 2.5, 5.0 mmol or “saturated Li” which meant to supply Li enough to leave a certain amount of it intact. Another Li-feeding method is continuous supply of Li by immersing Li foil in the solution during pre-doping, named “Li-supply.” The pre-doping time of the Si electrode was fixed at 24 h, and the pre-doped capacity was measured by a constant current discharge of 0.05 mA cm−2 between OCV and 1.5 V at 30℃. We employed spectroscopic method to analyze the solvation structure of the pre-doping solutions by FT-IR and UV-vis spectra. Figure 1 shows discharge voltage profiles for the Si electrodes pre-doped in Li-NTL solutions of different Li concentrations, which demonstrates clear dependency of pre-doped capacities on the Li concentrations. Li-supply delivered the largest pre-doped capacity among the four solutions. Figure 2 shows the UV-vis spectra of Li-NTL solutions with different Li concentrations. We focus two absorption bands at 320 nm and 550 nm in the spectra. The former is assigned to ion pair structure formed by radical anion of naphthalene and solvated Li+ ion [2], whose intensity decreased as Li concentration increased. The latter is assigned to the naphthalene dianion [3], whose intensity increased as the Li concentration increased. Thus, the results presented above evidently elucidate that the dianion plays a crucial role in Li pre-doping reactions.On our presentation, we will discuss the Li pre-doping reaction mechanism by adding more data on the characterization of the pre-doping solutions.[1] M. Saito et al., s of PRiME 2020, A02-0410 (2020).[2] M. Szwarc et al., J. Am. Chem. Soc., 98, 5707 (1976).[3] D. Vofsi et al., J. Polym. Sci. Polym. Chem. Ed., 20, 901 (1982). Figure 1

Li Pre-Doping of SiO Electrodes Using Li-Naphthalenide Solution for Next-Generation Batteries

SiO is regarded to be one of the promising anode materials to replace graphite in lithium-ion batteries (LIB) because of its higher specific capacity than graphite and better cycle stability than Si [1]. However, the large irreversible capacity is a serious problem which consumes charged capacity in vain during initial cycles. Therefore, Li pre-dope to dose Li to SiO beforehand has been proposed. In this study, our previous achievement on Li pre-doping to Si electrodes was much helpful. The highlights of the achievement are as follows [2, 3]. Li-naphthalenide (Li-NTL) was selected as a Li pre-doping agent.Li pre-doped capacity was much dependent on the solvent of Li-NTL solution.2-methyltetrahydrofuran (MeTHF) delivered the largest pre-doped capacity. Hence, we conducted this study on Li pre-doping to SiO electrodes by referring to the achievement on Si electrodes.SiO electrodes coated on Cu foil consisted of SiO, Ketjen Black, and polyimide binder in the ratio of 80 : 5 : 15 (m/m). Two types of SiO powder with an average particle size of 5 μmφwere used: carbon-coated SiO denoted as C-SiO and bare SiO which were purchased from OSAKA Titanium technologies Co., Ltd. We adopted 0.5 M NTL/MeTHF as a standard pre-doping solution based on our result of Li pre-doping to Si. SiO electrodes were confined in an air-tight cells with the pre-doping solution for 24 h to be pre-doped. The electrodes were taken out of the cells, rinsed in DMC, and used to assemble coin cells with Li counter electrodes, separators and electrolyte solution of 1.0 M LiPF6 / EC + DMC (1:1, v/v) + 10 wt% FEC. All of these processes were conducted in an Ar-filled glove box. Discharge/charge cycle test mode was constant-curent at 0.1 mA cm−2 between 0.02 and 1.5 V at 30 °C. Figure 1 shows charge/discharge performance of C-SiO electrodes with and without Li pre-doping. In Figure 1a, the OCV of the Li pre-doped electrode was as low as 0.2 V, which was much lower than that of the electrode without pre-doping, exceeding 2.0 V, and the charge capacity was nearly missing. However, the discharge capacity was not less than that of the electrode without pre-doping. This result reveals that SiO can be pre-doped effectively by Li-NTL/MeTHF, which is the same as Si. Figure 1b shows dQ/dV analysis results, in which the anodic curves for the with and without pre-doping are nearly identical. However, almost no cathodic curve is observed for the with pre-doping as shown in Figure 1a, while a sharp peak at 0.46 V assigned to formation of L x SiO y is observed for the without pre-doping [4]. A dashed curve inserted in the Figure 1b is the cathodic curve for the second cycle of the with pre-doping to complement the missing first cycle one. This curve shows no peak at 0.46 V and suggests formation of L x SiO y during pre-doping. We further analyzed the pre-doping reaction to elucidate the mechanism based on the result shown above. The detail of the results will be shown and discussed in our presentation.[1] M. N. Obrovac, V. L. Chevrier, Chem. Rev., 114, 11444 (2014).[2] M. Saito et al., s of PRiME 2020, A02-0410 (2020).[3] M. Saito et al., J. Electrochem. Soc., 166, A5174 (2019).[4] C. P. Grey et al., J. Am. Chem. Soc., 141, 7014 (2019). Figure 1

Improvements in Oxygen Diffusivity, ORR Activity and Durability of Pt-Based Catalysts By Mesoporous Carbon Support and Melamine Decoration

1. Introduction In Japan, an extremely high I-V performance is required for polymer electrolyte fuel cells (PEFCs) used in fuel cell electric vehicles after 2030 (red line in Figure 1) [1]. Therefore, we have to design Pt-based catalysts that have a high ORR activity and a durability as well as a high oxygen diffusivity [2]. In this study, the Pt-based catalysts were supported on a mesoporous carbon to increase oxygen diffusivity and the catalysts were decorated with melamine to improve ORR activity and durability [3, 4]. 2. Experimental Ketjen Black EC-300J (KB-300J: SBET: 922 m2/g, LION), Ketjen Black EC-600JD (KB-600JD: SBET: 1,345 m2/g, LION) and a mesoporous carbon (CNovel MH-18, SBET 1,334 m2/g, TOYO TANSO [5]) were used as carbon supports in the synthesis of PtCo alloy and Pd@Pt core-shell catalysts. A commercially available Pt/KB-300J catalyst (TEC10E50E, Pt size: 2.5 nm, Pt metal loading: 46.3 wt.%, TKK) was used as a reference catalyst. The PtCo alloy catalyst was synthesized by an oleylamine reduction method [6] and the Pd@Pt core-shell catalyst was synthesized by a direct displacement reaction method [7]. The metal loadings of Pt and Co in the alloy catalysts were 41 wt.% and 3 wt.%, respectively, and those of Pt and Pd in the Pd@Pt core-shell catalyst were 20 wt.% and 30 wt.%, respectively. The particle sizes of the PtCo alloy and the Pd@Pt core-shell catalyst NPs were 3.0 nm and 5.5 nm, respectively. CV of the catalyst was recorded at 25oC in Ar-saturated 0.1 M HClO4 with a potential scan rate of 50 mV/s and LSV was measured by RDE method at 25oC in O2-saturated 0.1 M HClO4 with a potential scan rate of 10 mV/s at a rotation speed of 1,600 rpm. An accelerated durability test (ADT) of the catalysts was conducted by a square wave potential cycling of 0.6 V (3 s)-1.0 V (3 s) vs. RHE performed in Ar-saturated 0.1 M HClO4 at 80oC for 10,000 cycles with and without melamine addition (10 µM to the electrolyte). MEA was fabricated by a decal method using a reinforced membrane (12 µm in thickness, Gore) and a GDL (TORAY). Nafion® DE2020 was used as an ionomer for the catalyst ink preparation (I/C: 0.83). I-V performance of a single cell was evaluated at 80oC, 75% RH by using the MEA with an active area of 1 cm2 in which the Pt loading in the cathode catalyst layer was set to 0.1 mg-PGM/cm2. H2 gas (418 NmL) and air (998 NmL) were supplied to the anode and the cathode, respectively, and the H2 gas was pressurized to 150 kPa at the gas-outlet (H2 utilization: 5% at a current density of 3.0 A/cm2). 3. Results and Discussion Pore size distribution of the carbon supports is summarized in Figure 2. KB-300J has no clear mesopores, while KB-600JD and CNovel MH-18 have the mesopores. Figure 1 shows I-V performance of Pd@Pt core-shell catalysts, indicating that Pt/Pd/CNovel MH-18 catalyst exhibits a superior cell performance to that of Pt/Pd/KB-600JD catalyst. Connectivity of mesopores in KB-600JD and CNovel MH-18 supports analyzed by 3D-TEM is shown in Figure 3. It is clear that the connectivity in CNovel MH-18 support is much higher than that in KB-600JD support, which is considered to contribute to the superior I-V performance of Pt/Pd/CNovel MH-18 catalyst observed in Figure 1.Figures 4 depicts morphological change of PtCo/CNovel MH-18 alloy catalyst by ADT performed at 80oC for 10,000 cycles. A very small amount of melamine addition to the electrolyte (10 µM) notably suppressed the catalyst NPs agglomeration in ADT, which significantly mitigated ECSA decay of the catalysts. More importantly, Co dealloying of the PtCo alloy catalyst in ADT was remarkably suppressed by the melamine addition, and thus the alloy catalyst retained a high ORR mass activity even after ADT. Therefore, we believe that the target cell performance as well as the high durability of the Pt-based catalysts can be realized by combination of the mesoporous carbon support and the decoration with melamine or melamine derivatives.This study was partly supported by NEDO, Japan.

Synergy of Mediator and LiNO3 in Electrolyte Solution and Analysis of Reaction Mechanisms on Li-Air Battery Performance

Li-air batteries (LAB) have a theoretical energy density of 3500 Wh kg− 1, overwhelming that of Li-ion batteries, due to the Li metal anode and atmospheric oxygen fed to the air electrode (AE). Therefore, they have been attracting much attention because of the potential longer cruising range of electric vehicles, although many problems are still left to be solved. The most serious one among them is large charge overvoltage of AE due to the low reactivity of discharge product Li2O2, which induces clogging of the air electrode during repeated discharge/charge cycles, decomposition of the electrolyte solution, and air electrode corrosion. Redox mediator (RM) to reduce the charge overvoltage is widely studied nowadays, while RM+ generated at AE diffuses and reacts with Li negative electrode to cause shuttle effect [1, 2]. In this study, we employed both RM to reduce the charge overvoltage and LiNO3 as an electrolyte salt in tetraglyme (G4)-based electrolyte solution to modify the Li surface into Li2O as a protector against shuttle effect [3]. We further applied RM-coating on AE to stabilize the cell performance and suppress the shuttle effect [4].AE consisted of Ketjen Black, PVDF binder, and MPT (10-methylphenothiazine) as an RM coated on a carbon paper substrate. Two types of electrolyte solutions were used: 1.0 M LiNO3/G4 with and without MPT. Three cell configurations with different combinations of AE and electrolyte solution were assembled: “RM-free” without MPT, “MPT-in-EL” containing MPT in the electrolyte solution, and “MPT-on-AE” with MPT coated on AE. The amount of RM dosed on AE was adjusted to be the same as that dissolved in the electrolyte solution of the MPT-in-EL cell. The cell components, AE of 2 cm2, a separator, a Li negative electrode and an electrolyte solution, were stacked and contained in an air-tight test cell, which was supplied with pure O2 gas of 1.0 mL s− 1 at 50 oC. The discharge/charge cycle test mode was constant current-constant capacity of 200 mA gKB − 1 and 500 mAh gKB − 1 between 2.0 V and 4.5 V. Figure 1 shows cross sections of discharge/charge voltage profiles at the midpoit of 250 mAh gKB − 1 of the three cells, RM-free, MPT-in-EL, and MPT-on-AE. MPT-on-AE revealed better performance with the less overvoltages in both charge and discharge than the others, although slight degradation was indicated even in MPT-on-AE by the 15th cycle. While we could conceive various causes for the degradation such as dissolution of the coated MPT, decomposition of MPT, and covering of AE with deposits, we started with the quantitative analysis of the dissolved MPT from the coated MPT. Figure 2 shows the results of colorimetric analysis of MPT on AE before discharge, which evaluates the dissolved amount of the coated MPT. A calibration line was obtained by dissolving MPT in 1.0 M LiNO3/G4 base solution. MPT sample was extracted from MPT-on-AE cell after 1 h rest following cell assembly by means of centrifugal separation. The results showed that half of the coated MPT eluted immediately. However, SEM-EDS analysis evidenced no trace of shuttle effect, suggesting local high concentration of the applied MPT near the AE. Other analytical results concerning degradation causes will be reported on the presentation.This study was supported by JST Project ALCA-SPRING (JPMLAL1301) and NIMS Joint Research Hub Program, Japan.[1] S. Ha et al., J. Mater. Chem. A, 5, 10609 (2017).[2] Y. Hayashi et al., J. Electrochem. Soc., 167, 020542 (2020).[3] M. Saito et al., J. Electrochem. Soc., 168, 010520 (2021).[4] Y. Hayashi, M. Saito et al., Electrochemistry, 89, 557-561 (2021). Figure 1

(PEFC&E 2022 Student Poster Award Winner - 1st Place) MEA Performance of Pd@Pt Core-Shell Catalysts Supported on Different Particle Sizes of Mesoporous Carbon

1. Introduction Very high performance, especially on output power density (6 kW/L), for PEFCs in FCVs is targeted for 2030 in Japan [1]. Therefore, we need to improve not only ORR activity, but also oxygen diffusivity of Pt-based cathode catalysts for PEFCs. In this study, highly interconnected mesoporous carbon (MPC) [2] was selected as a support of Pd@Pt core-shell catalyst. The Pd@Pt core-shell catalyst NPs were supported on different particle size of the MPC and cell performance was investigated. 2. Experimental We selected CNovel®MH-18 (central mesopore diameter: 4 nm, SBET: 1,334 m2/g, TOYO TANSO) as a MPC support. As-received MPC with an average size of ca. 2 μm was pulverized to ca. 800, 450, and 250 nm by a wet bead-milling process. The Pd core NPs were loaded on MPCs by an impregnation-thermal reduction method and the Pt shell was formed on the Pd core NPs by a direct displacement reaction method [3]. Characterizations of the MPC, the Pd/MPC cores and the Pt/Pd/MPC catalysts were conducted by N2 gas adsorption, TG-DTA, XRD, XRF, TEM, SEM, CV and the ORR activity of the catalysts was evaluated by the RDE method. MEAs with 1×1 cm2 were fabricated by a decal method using a reinforced membrane (12 µm in thickness, Gore) and a GDL (TORAY). The Pt metal loading at the cathode was 0.1 mg-Pt/cm2. Nafion® DE2020 was used as an ionomer for the catalyst ink preparation (I/C was set to 0.83). I-V performance was evaluated at 80oC, 35-95% RH. H2 gas (418 mL/min.) and air (998 mL/min.) were supplied to the anode and the cathode, respectively, and H2 gas was pressurized to 150 kPa (ambient + 50 kPa) at gas-outlet. 3. Results and Discussion N2 gas adsorption data were analyzed by the t-plot method and the changes in the total, external and internal surface area of the MPCs pulverized for different times are shown in Figure 1. It was shown that the total and the external surface area increased, while the internal surface area decreased with pulverization time. These results suggest that fresh surface was newly formed by the pulverization, and the fraction of the internal surface was decreased. Figure 2 shows cross-sectional TEM images of the Pt/Pd/MPC catalysts using different sizes of MPC supports (ca. 2,000, 800, 450 and 250 nm), which indicates that the catalyst NPs were uniformly supported throughout the interior of MPC regardless of the particle size of MPC. The ECSA of the Pt/Pd/MPC catalysts changed little with the particle size of MPC (ca. 120 m2/g-Pt), while the ORR mass activity at 0.9 V was the highest (1,533 A/g-Pt) when the catalyst NPs were supported on relatively large MPC (800 nm).I-V curves at 80oC, 35% RH of the MEAs using the Pt/Pd/MPC cathode catalysts using different sizes of MPC supports are demonstrated in Figure 3. Interestingly, the cell voltage was higher over the entire current density range for Pd@Pt catalysts using MPCs with larger particle sizes (2000 and 800 nm). This tendency was also observed at a high relative humidity of 95% RH. These results suggest that the Pd@Pt catalyst NPs supported on larger MPC (2,000 and 800 nm) contributed to ORR in the high current density range even when the relative humidity was low. Figure 4 compares the connectivity of mesopores in Ketjen Black EC-600JD (KB-600JD, LION) and CNovel® MH-18 visualized from 3D-TEM observation results. It is clear that the MPC has a higher mesopore’s connectivity than KB-600JD. Figure 5 shows cross-sectional SEM images of the Pt/Pd/MPC. Larger pores were observed inside of the MPC support. Therefore, it is considered that the high connectivity of the mesopores and the presence of larger pores inside of the MPC support contributed to the superior I-V performance observed in MEAs using the catalysts supported on MPCs with particle size of ca. 2,000 and 800 nm. At present, it is not clear why the catalysts supported on smaller MPCs (450 and 250 nm) exhibited inferior I-V performance, though the oxygen diffusion inside MPCs should be easier than that for larger ones.This study was partly supported by NEDO, Japan. The CNovel®MH-18 supports with different size were supplied by Dr. Shodai of TOYO TANSO.

(Digital Presentation) Evaluating the Performance of Multi-Walled Carbon Nanotube Composite Microporous Layers Deposited on Carbon Felt Gas Diffusion Layers

Electrochemical energy storage devices (EESDs) such as metal-air batteries (MABs) and alkaline electrolyte membrane fuel cells (AEMFCs) have begun to gain vast amounts of attention due to their high theoretical energy densities and open-circuit voltage values. Although these devices present promising aspects for the environment and sustainability, they suffer from the slow reaction kinetics and degradation effects that occur at the catalyst layer interface of the air electrode. Typically, these effects are due to the accumulation of molecular species such as water or oxygen at catalyst active sites because of poor electrode hydrophobicity and fluid management. Herein, we perform experimentation to mitigate these effects by implementing mixed carbon composite microporous layers onto porous carbon felt based air electrodes. This adaptation of the air cathode was predominantly based on the aforementioned downfalls and the lack of availability of commercial carbon felts that have adequate wet proofing and conductivity like some of the related carbon paper gas diffusion layers. Microporous layers (MPLs) enhance electrical conductivity, surface area, and adhesion at the catalyst layer and gas diffusion layer interface. These layers typically consist of a hydrophobic polymer such as polytetrafluoroethylene (PTFE) and a conductive carbon black substrate such as Ketjen Black 600JD (KJB). The incorporation of multi-walled carbon nanotube (MWCNT) and carbon black composites into the structure of the MPLs drastically decreases ohmic polarization with minimal increases in specific resistance. The electrical resistance of the synthesized carbon substrate decreases at high rates of MWCNT dispersion, which corresponds directly to a low MWCNT weight percentage within the composite. The MPL increases the mass transport through the electrode by mitigating flooding effects that typically occur within the pores near the surface of the catalyst layer, ultimately aiding in charge transfer between the gas diffusion layer and catalyst active sites. Preliminary data from AEMFC symmetric cell tests suggests that a microporous layer consisting of a 10 wt.% MWCNT/KJB (m/m) substrate is the optimal loading of carbon nanotubes and leads to better cell performance. There is an increase in current density of 60 mA/cm2 compared to an air electrode with no MPL within the ohmic region of the polarization curve corresponding to approximately 0.7 V, while only an increase of 18 mA/cm2 is seen for an MPL consisting of a 30 wt.% MWCNT/KJB (m/m) carbon substrate. The increase of charge transfer by the 10 wt.% synthesized carbon substrate MPL was attributed to the ability of the nanotubes at high rates of dispersion to act as molecular wires within the electrode. Additionally, zinc-air battery tests using the optimally configured air electrode, determined from previous experiments, show that the current density at an operating voltage of 1.1 V was increased by 2.3 times that of an electrode without an MPL using the same catalyst material and loading. Significantly, this research will lead to a better understanding of optimization of the air electrode used within electrochemical devices and how to eliminate some of the adverse effects associated with it. Figure 1

Synthesis of Single-Atom and Dual-Atom Catalyst Using N-Defective C3N4

Single-atom catalysts, which have been studied tremendously in the past decade, are emerging as a new class of heterogeneous catalysts. It is now generally known that defect sites play an important role in forming single-atomic structures. In the case of SACs, defective sites provide not only space for fixation of metal precursor, but also electrons for stabilizing positive metal ions. Graphitic carbon nitride (g-C3N4) is one of the ideal 2D materials for the synthesis of SACs. C3N4 has enough anchoring sites which originate from the ordered structure of tri-s-triazines connected together. Furthermore, abundant nitrogen atoms in C3N4 can provide electrons to single metal atoms. however, C3N4 is unsuitable as support for electrochemical catalysts due to its low electrical conductivity. Therefore, we made a C3N4 shell on the outer surface of carbon black (Ketjen Black EC-600JD) to obtain conductive support (C@C3N4).[1] Pt was supported on C@C3N4 at 1, 2, 4, and 8 wt% by wetness impregnation method. Through XRD, HAADF-STEM, and XAFS analysis, it was confirmed that a single-atomic structure was formed only when the Pt content was 1 or 2 wt%. In addition, I confirmed that the H2O2 selectivity (%) in the electrochemical oxygen reduction reaction was different according to the Pt content of the catalysts.In terms of controlling reaction sites at the atomic level, the challenge above creating single-atomic structures is creating structures in which two or three atoms are formed as dimer or trimer. Unlike single-atom catalysts, in a dimer or trimer structure, two or more atoms are adjacent to each other, so they can exhibit completely different catalytic properties. Finely controlling the defect site of the support can be a good strategy. Therefore, I adopted the strategy of making a defect in C3N4 to synthesize a dimer structure. It has been reported that N-vacancy can be selectively formed on C3N4 by additional heat treatment with NaBH4.[2, 3] In addition, DFT calculation results have been reported that Pd-Cu dimer structure can be stably formed on nitrogen-defective C3N4.[4]In this work, I create N-vacancy on a Pt1/C@C3N4 by additional heat treatment with NaBH4, and Co atoms were deposited as a secondary transition metal. The research strategy was to anchor the Co atom to the N-vacancy formed around the Pt single-atom, resulting in the formation of a dimer structure. First of all, the formation of N-vacancy on C@C3N4 support was clearly confirmed by FT-IR and XPS analysis. To confirm the dimer structure of Pt and Co, XAFS analysis was conducted. As a result, although not all Pt and Co atoms formed a dimer structure due to the limitation of the synthesis method, the intended structure of Co atom connected to a Pt atom was confirmed. In the Pt L3 edge EXAFS, a peak arising from Pt-Co scattering was observed at 2.4 Å. Furthermore, to confirm that PtCo alloy particles were not formed, high-result HAADF-STEM images were taken. All metal atoms were atomically dispersed, and nanoparticles were not found. This research demonstrated that defect engineering on support material can successfully modify active site on the atomic scale.

Detection of rare CTCs by electrochemical biosensor built on quaternary PdPtCuRu nanospheres with mesoporous architectures

Circulating tumor cells (CTCs) are promising liquid biopsy biomarkers for early cancer detection and anti-cancer therapy evaluation. The ultra-low abundance of CTCs in blood samples requires highly sensitive and accurate detection ways. In this study, we propose the design of a dual-recognition electrochemical biosensor to improve both the specificity and signal response. PdPtCuRu mesoporous nanospheres (PdPtCuRu MNSs) with excellent three dimensions (3D) nanopore structures were synthesized by one-pot method and connected to mucin 1 (MUC1) aptamer to serve as signal amplification probe. Besides, superconductive carbon black, Ketjen Black (KB), and gold nanoparticles (AuNPs) modified organometallic frame (CeMOF-Au) were combined to work as signal transducer. The characteristic branching structure of KB provides abundant contact points to load CeMOF-Au to heighten the interface electron transfer rate. In addition, AuNPs were reduced on the surface of CeMOF, which could effectively bind the capture antibody and further enhance the conductivity. Under the optimized condition, the limit of detection (LOD) of the as-constructed biosensor was less than 10 cells mL−1 for model A549 cells, and showed good specificity and accuracy in spiked serum samples. We envision the as-proposed electrochemical biosensor would alternate as a useful tool for the clinical detection of CTCs for cancer diagnosis.

Rationalizing nitrogen-doped secondary carbon particles for practical lithium-sulfur batteries

Nanostructured carbon host materials are widely used to improve both sulfur utilization rate and reaction kinetics in lithium-sulfur (Li-S) batteries. However, high complexity/cost of materials synthesis and difficulty in processing nano-materials into high-mass-loading electrodes are still significant barriers to the development of low-cost and high-energy Li-S batteries. In this study, we reported a generic and scalable synthesis approach to prepare nitrogen-doped secondary carbon particles. By using nitrogen-containing precursor as an integration reagent, the nanosized Ketjen Black particles were integrated into micron-size secondary ones and nitrogen-doped (NKB) simultaneously through a one-step heat treatment. With NKB as an example material, the effects of particle integration degree on the secondary particles’ structures, pore volume and connectivity, sulfur loading capability, and cell performance were studied and discussed. At an optimal integration condition, the NKB particles had significantly improved particle dimensions with well-maintained high specific surface area and pore volume. Contributed by the micron size and high pore volume, the NKB/S were successfully used for high-sulfur-loading cathode coating (4–7 mgs cm−2) and were able to deliver a specific capacity of ∼1100 mAh g−1 at a practical low-porosity (50 %) and lean-electrolyte conditions (E/S =4 µL mg−1). Feasibility of the materials for practical use was validated through scaling up synthesis (40 g/batch), large-area electrode coating, and practical pouch cell (1.6 Ah) assembly and test.

MOFs/Ketjen Black-Coated Filter Paper for Spontaneous Electricity Generation from Water Evaporation.

Metal-organic frameworks (MOFs) have the advantages of tunable pore sizes and porosity and have demonstrated unique advantages for various applications. This study synthesized composite MOF nanomaterials by modifying MOF801 or AlOOH with UIO66. The composite nanomaterials, UIO66/MOF801 and UIO66/AlOOH showed increased Zeta potential than their pristine form, AlOOH, UIO66 and MOF801. For the first time, the composite MOFs were used to fabricate filter paper-based evaporation-driven power generators for spontaneous electricity generation. The MOFs-KBF membrane was constructed by coating filter paper (10 × 50 mm) with composite MOFs and conductive Ketjen Black. The UIO66/MOF801 decorated device achieved a maximum open circuit voltage of 0.329 ± 0.005 V and maximum output power of 2.253 μW. The influence of salt concentration (0.1–0.5 M) on power generation was also analyzed and discussed. Finally, as a proof-of-concept application, the device was employed as a salinity sensor to realize remote monitoring of salinity. This work demonstrated the potential of flexible MOF composites for spontaneous power generation from water evaporation and provides a potential way to enhance the performance of evaporation-driven power generators.

Hybridization of Mesoporous Carbon and Iron Oxide for Better Mitigation of Polysulfide Shuttling in Li-S Batteries

With a higher theoretical capacity, lithium-sulfur (Li-S) batteries have been considered as promising candidates for next-generation batteries. Due to the non-conducting nature of sulfur, however, lithium-sulfur batteries tend to exhibit poor performance at a high current rate (C-rate).Here we demonstrate that Fe3O4, synthesized from precursor iron (III) acetylacetonate (AAI), and mesoporous carbon material, Ketjen Black (KB), can be synergistically combined to enhance the electrochemical performance of lithium-sulfur batteries substantially. Instead of adding commercial magnetite particles into Li-S cathodes, iron oxides are synthesized and imbedded into KB from a precursor, AAI, through thermal treatments in air and Ar. The sulfur, then, is incorporated into iron oxides/KB hybrids by melting at an elevated temperature. With air-controlled electrospray as the processing method, sulfur embedded iron oxides/KB, poly(acrylic acid), and rGO sheets are mixed and directly deposited onto the carbon-coated aluminum collector, to employ as the Li-S battery cathode. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) studies confirm that Fe3O4 and iron carbide (Fe3C) are synthesized from the precursor, AAI, embedded in mesoporous carbon materials, and reducing the charge transfer resistance of batteries. The rate-capability tests show that systems with KB/Fe3O4 can achieve enhanced performance compared to batteries without iron oxides, especially at high C-rates. With 14 wt % of solid materials as iron oxides and iron carbide, batteries exhibit 750 mAh/g at 2C discharge/charge rates, which is 83% higher compared to systems without iron oxides. However, incorporated via 250 °C for 0.5 hr in air and 850 °C for 2 hr in Ar, the composite of KB/Fe3O4/Fe3C induces irreversible side reactions during the initial charging process, which causes a huge difference in capacity between the first and the second cycle. To achieve an optimal status with improved rate capability and acceptable initial charging time, we modify the thermal treatments and thus increase the proportion of Fe3O4 in the mixture. According to the postmortem analysis, cathodes with iron oxides can interact with soluble polysulfides strongly and alleviate the polysulfide shuttle effect significantly, compared with those without Fe3O4. Such enhanced rate capability by KB/Fe3O4 (synthesized) over KB only or KB/Fe3O4 (commercial) systems suggests that the incorporation of iron oxides can play an important role in improving the electrical conductivity of cathode and mitigating polysulfide shuttle effect. Figure 1

ORR Activity and Stability of a Carbon-Supported Ptxy Alloy Catalyst Evaluated in a PEM Fuel Cell

The application of proton exchange membrane fuel cells (PEMFCs) in light-duty vehicles (LDV) has dominated the fuel cell research field for the past decades. To reduce the LDV FC system cost to 30 $/kW by 2025 has driven the search for highly active cathode catalysts that could substitute the costly state-of-the-art Pt-alloy catalysts or reduce the cathode loadings to < 0.125 mgPt/cm2.1, 2 As novel ORR catalyst continue to emerge, theoretical calculations have turned the attention on Pt-rare earth (RE) alloys, such as platinum-yttrium alloys that were suggested to have superior activity for the oxygen reduction reaction (ORR) and superior long-term stability compared to conventional carbon-supported platinum catalyst (Pt/C). 3 Based on these findings, many attempts have been made to produce high electrochemical surface area (ECSA) Pt-RE alloy catalysts.4 In recent years, Hu, et al. introduced a new synthesis procedure that utilizes a carboiimide-assisted synthesis for the preparation of Pt-RE/C catalysts with an unprecedentedly high ECSAs in the range of ~50-60 m2/gPt.5 With such high ECSA PtxY/C catalysts, good PEMFC performance would be expected, but to date the ORR activity and stability of such PtxY/C catalysts has not been demonstrated in a PEMFC environment.In view of this, we reproduced the synthesis reported by Hu et al. using a Ketjen Black (KB) carbon support. The resulting PtxY/KB catalyst was characterized by X-ray diffraction, X-ray spectroscopy (EDS) in scanning transmission electron microscopy (STEM), and elemental analysis, indicating the formation of a Pt-richshell/Pt3Ycore structure that was caused by the acid washing procedure introduced before the electrochemical characterization.5 In our present study, two different Pt/KB catalysts were selected as reference materials: i) a Johnson Matthey reference catalyst consisting of small well-dispersed Pt nanoparticles on a KB support (Pt/KB-JM); ii) an in-house synthesized Pt/KB catalyst (Pt/KB-syn.) with a similar particle size distribution and ECSA as the in-house synthesized PtxY/KB catalyst (PtxY/KB-syn.). The ECSA (via CO-stripping voltammetry) and the ORR mass activity at 0.9 V vs. RHE (imass 0.9 V) of these three catalysts were first evaluated by rotating disk electrode (RDE) measurements in 0.1 M HClO4 at 25 °C. The catalysts were also incorporated as cathode catalysts in membrane electrode assemblies (MEAs), first determining their ECSA (by CO-stripping) and then their H2/O2 and H2/air performance in a 5 cm2 single-cell PEMFC hardware at 80 °C under differential flow conditions, including a quantification of the ORR mass activity at 0.9 V vs. RHE at 100 kPa O2.As can be seen in Figure 1, the relative ECSA and ORR mass activity values of the three different catalysts obtained in the RDE and the PEMFC configuration were essentially identical when evaluated at the same ionomer to carbon ratio (I/C = 0.7, g/g). Furthermore, a comparison of the RDE ORR activity at two different I/C ratios showed that the PtxY/KB-syn. and Pt/KB-syn. catalysts were more susceptible to ionomer poisoning when compared to the Pt/KB-JM catalyst. Following the approach taken in our previous publications, the voltage-cycling stability of the synthesized catalysts was also evaluated using an accelerated stress test (AST) consisting of a triangular potential scan between 0.6 and 1.0 VRHE at 50 mV/s up to 30000 cycles.5 Overall, the RDE and PEMFC data showed that the here synthesized carbon-supported Pt-richshell/Pt3Ycore catalyst does not shown an enhanced ORR activity nor a long-term stability benefit when compared to a Pt/KB catalyst with the same ECSA, contrary to what had been hypothesized earlier.3 References R. L. Borup, A. Kusoglu, K. C. Neyerlin, R. Mukundan, R. K. Ahluwalia, D. A. Cullen, K. L. More, A. Z. Weber and D. J. Myers, Current Opinion in Electrochemistry, 21, 192–200 (2020).M. Escudero-Escribano, K. D. Jensen and A. W. Jensen, Current Opinion in Electrochemistry, 8, 135–146 (2018).J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson, H. A. Hansen, T. F. Jaramillo, J. Rossmeisl, I. Chorkendorff and J. K. Nørskov, Nature Chemistry, 1(7), 552–556 (2009).J. N. Schwämmlein, G. S. Harzer, P. Pfändner, A. Blankenship, H. A. El-Sayed, and H. A. Gasteiger, Journal of the Electrochemical Society(165 (15)), J3173-J3185 (2018).Y. Hu, J. O. Jensen, L. N. Cleemann, B. A. Brandes and Q. Li, Journal of the American Chemical Society, 142, 953–961 (2020). Acknowledgment This work has been supported by the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No. 826097 (GAIA). This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe Research. Figure 1

(Digital Presentation) Improved Nanocatalysts, Supported IrOx and IrRuOx, for Enhanced Oxygen Evolution Reaction

The production of hydrogen via acidic electrochemical water splitting is an important pillar towards more sustainability. The overall water electrolysis is hindered by the slow kinetics of the oxygen evolution reaction (OER). Therefore, the catalyst material for the anode still requires optimization. Hereby, we present two highly active OER catalysts, IrOx and Ir0.4Ru0.6Ox nanoparticles (NPs), prepared by a straightforward, surfactant-free, colloidal synthetic route.1 The metallic NPs are ~1.5 nm in diameter and were deposited on carbon Ketjen Black (CKB) as well as on antimony doped tin oxide (ATO) to investigate the active phase as well as potential influences of the support material. After the colloidal synthesis and supporting, the catalysts were activated, thus undergoing a particle growth of ~1 nm. Their performance was benchmarked in terms of activity and stability using our recently developed electrochemical flow cell called gas diffusion electrode (GDE) setup.2 This novel approach allows closing the experimental gap between the two most common methods, namely the rotating disk electrode (RDE) and the membrane electrode assembly (MEA). Independently from the support, Ir0.4Ru0.6Ox shows a higher activity towards OER than IrOx at three tested temperatures, i.e. 30, 40, 60 °C. The two different support materials were also compared, and it was found that independently from the material, NPs deposited on CKB showed slightly higher activity at low current densities (up to 40 mA mgIr -1). As expected, accelerated potentiostatic stability test reveals a rapid degradation of the IrOx/CKB, while IrOx/ATO and Ir0.4Ru0.6Ox/ATO exhibit similar stability than commercially available Ir black.[1] Francesco Bizzotto, Jonathan Quinson, Alessandro Zana, Jacob J. K. Kirkensgaard, Alexandre Dworzak, Mehtap Oezaslan, Matthias Arenz, Catal. Sci. Technol., 2019, 9, 6345-6356.[2] Johanna Schröder, Vladislav A. Mints, Aline Bornet, Etienne Berner, Mohammad Fathi Tovini, Jonathan Quinson, Gustav K. H. Wiberg, Francesco Bizzotto, Hany A. El-Sayed, Matthias Arenz, JACS Au, 2021, 1, 247-251. Figure 1