Higher Mass Specific Activity Research Articles

Preparation and Characterization of Platinum-Cobalt Nanosheets for Oxygen Reduction Reaction

Enhancing the efficiency of Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is crucial for the broader use of polymer electrolyte fuel cells. Pt-based electrocatalysts are commonly used at the cathode side of polymer electrolyte fuel cells to facilitate the ORR, which is the most sluggish process during cell operation. Pt nanosheet prepared via topotactic reduction of platinum oxide nanosheets showed large electrochemically active surface area (ECSA)and high mass specific activity (MA).1 The addition of cobalt into the Pt nanosheet is expected to enhance and improve overall electrocatalytic performance as PtCo alloy nanoparticles are known to have higher specific activity than pure Pt. In this study, we present the synthesis and characterization of cobalt-doped platinum-oxide nanosheets ((Pt,Co)Ox NS) and their transformation into carbon-supported Pt-Co nanosheets for potential electrochemical applications.The (Pt,Co)Ox NS colloid was obtained through exfoliation in aqueous solution by modification of our previous synthesis process.1 The results demonstrated enhanced electrocatalytic activity of the (Pt,Co)Ox NS composite compared to pure platinum-oxide nanosheets. For the pure platinum-oxide nanosheets, the ECSA was 97 m2 (g-Pt)-1. Moreover, employing the Koutecky-Levich equation, the MA was determined to be 321 A g-1 at 0.9 V vs. RHE, and the specific activity was 332 µA cm-2. For the PtCo nanosheets, the ECSA was similar at 91 m2 (g-Pt)-1. However, owing to the Co electronic effect, the specific activity rose to 576 µA cm-2, leading to an overall increase in MA to 524 A g-1 at 0.9 V vs. RHE. This improvement is attributed to the synergistic effect between cobalt and platinum, which enhances the oxygen reduction process. Reference: D. Takimoto, S. Toma, Y. Suda, T. Shirokura, Y. Tokura, K. Fukuda, M. Matsumoto, H. Imai, and W. Sugimoto, Nat Commun 14, 19 (2023)

Carbon-anchoring synthesis of Pt1Ni1@Pt/C core-shell catalysts for stable oxygen reduction reaction

Proton-exchange-membrane fuel cells demand highly efficient catalysts for the oxygen reduction reaction, and core-shell structures are known for maximizing precious metal utilization. Here, we reported a controllable “carbon defect anchoring” strategy to prepare Pt1Ni1@Pt/C core-shell nanoparticles with an average size of ~2.6 nm on an in-situ transformed defective carbon support. The strong Pt–C interaction effectively inhibits nanoparticle migration or aggregation, even after undergoing stability tests over 70,000 potential cycles, resulting in only 1.6% degradation. The stable Pt1Ni1@Pt/C catalysts have high oxygen reduction reaction mass activity and specific activity that reach 1.424 ± 0.019 A/mgPt and 1.554 ± 0.027 mA/cmPt2 at 0.9 V, respectively, attributed to the optimal compressive strain. The experimental results are generally consistent with the theoretical predictions made by our comprehensive microkinetic model which incorporates essential kinetics and thermodynamics of oxygen reduction reaction. The consistent results obtained in our study provide compelling evidence for the high accuracy and reliability of our model. This work highlights the synergy between theory-guided catalyst design and appropriate synthetic methodologies to translate the theory into practice, offering valuable insights for future catalyst development.

Platinum/Platinum Sulfide on Sulfur-Doped Carbon Nanosheets with Multiple Interfaces toward High Hydrogen Evolution Activity.

Platinum (Pt)-based materials are among the most competitive electrocatalysts for the hydrogen evolution reaction (HER) due to suitable hydrogen adsorption energy. Due to the rarity of Pt, it is desirable to develop cost-effective Pt-based electrocatalysts with low Pt loading. Herein, Pt/PtS electrocatalysts on S-doped carbon nanofilms (PPS/C) have been successfully fabricated through a precursor reduction route with a complex of Pt and 1-dodecanethiol (1-DDT) as the precursor. The PPS/C achieved at 400 °C (PPS/C-400) exhibits excellent HER performances with an ultralow overpotential of 41.3 mV, a low Tafel slope of 43.1 mV dec-1 at a current density of 10 mA cm-2, and a long-term stability of 10 h, superior to many recently reported Pt-based HER electrocatalysts. More importantly, PPS/C-400 shows a high mass-specific activity of 0.362 A mgPt-1 at 30 mV, which is 1.88 times of that of commercial 20% Pt/C (0.193 A mgPt-1). The introduction of sulfur leads to the formation of PtS, which not only reduces the content of Pt but also realizes the interface regulation of Pt/PtS, as well as the doping of carbon. Both regulations make the resulting catalyst have abundant active centers and rapid electron transfer/transport, which is conducive to balancing the adsorption and resolution of intermediate products, and finally achieving great mass-specific activity and stability. The research work may provide ideas for designing effective Pt-based multi-interface electrocatalysts.

Ligand effect of PdRu on Pt-enriched surface for glucose complete electro-oxidation to carbon dioxide and abiotic direct glucose fuel cells.

The development of advanced electrocatalysts for the abiotic direct glucose fuel cells (ADGFCs) is critical in the implantable devices in living organisms. The ligand effect in the Pt shell-alloy core nanocatalysts is known to influence the electrocatalytic reaction in interfacial structure. Herein, we reported the synthesis of ternary Pt@PdRu nanoalloy aerogels with ligand effect of PdRu on Pt-enriched surface through electrochemical cycling. Pt@PdRu aerogels with optimized Pt surface electronic structure exhibited high mass activity and specific activity of Pt@PdRu about 450 mA·mgPt-1 and 1.09 mA·cm-2, which were 1.4 and 1.6 times than that of commercial Pt/C. Meanwhile, Pt@PdRu aerogels have higher electrochemical stability comparable to commercial Pt/C. In-situ FTIR spectra results proved that the glucose oxidation reaction on Pt@PdRu aerogels followed the CO-free direct pathway reaction mechanism and part of the products are CO2 by completed oxidation. Furthermore, the ADGFC with Pt@PdRu ultrathin anode catalyst layer showed a much higher power density of 6.2 mW·cm-2 than commercial Pt/C (3.8 mW·cm-2). To simulate the blood fuel cell, the Pt@PdRu integrated membrane electrode assembly was exposed to glucose solution and a steady-state open circuit of approximately 0.6 V was achieved by optimizing the glucose concentration in cell system.

Metal edge confined platinum atoms in metal/hydroxide hierarchy structure for multiple hydrogen conversion and evolution

Single-atom catalysts (SACs), as a thriving subfield of catalysis, have progressed tremendously. However, the contradiction between the isolated dispersion feature of metal sites and the high mass-specific activity of the catalyst inhibits the advances of the SACs. Herein, the Pt atoms are confined at the metallic Co phase edge in two-dimensional Co/Co(OH)2 hierarchy structure (PtSA-Co@Co-Co(OH)2) by the defect inducted order electrodeposition strategy. Both integrations of in-situ/ex-situ experimental characterizations and theoretical calculation reveal that such metal edge confined Pt atoms possess an enlarged atom exposure ratio, high stability, and the like-metal electronic state contributed by metal Co 3d, which enables the Pt atoms with more suitable affinity to simultaneously bind the multiple H atoms for durable H*-H2 conversion and H2 evolution. Moreover, the metallic PtSA-Co collaborated Co/Co(OH)2 interfaces demonstrate a strong H2O dissociation capacity by the preference adsorption of H* on metallic PtSA-Co and OH*on Co/Co(OH)2 interfaces. Combining a further enhancement of constructing the catalysts on an Ag nanowire network to form a seamlessly conductive nanostructure, the PtSA-Co@Co-Co(OH)2 achieves a high mass activity with 5.92 A mg−1 at the overpotential of 100 mV in alkaline condition, 37 times to that of the benchmark Pt/C catalyst and significantly outperforming the reported catalysts. While our work has focused on the hydrogen evolution reaction, this class of metal edge collaborated single-atom catalysts may be conducive to unlock the low mass-specific activity of atomically dispersed catalysts for various processes, such as oxygen evolution reactions (OER), CO2 reduction, and biomass conversion, etc.

S-doped carbon anchoring PtCo intermetallic nanoparticles for efficient proton exchange membrane fuel cells based on molecularly engineered design

Enhanced ordered intermetallic compounds excel in catalyzing the oxygen reduction reaction (ORR). We introduce a novel synthesis strategy based on molecularly engineered to address challenges in high-temperature annealing. It involves the synthesis of carbon platforms with rich edge sites, which serve as effective anchoring points for nanoparticles. By utilizing sulfur anchoring, we synthesize ordered Pt–Co intermetallic with Pt-rich shells (o-PtCo@Pt) that exhibit remarkable ORR performance. Ordered arrangement of Pt–Co endows Pt-shell with compression stress and enhances the oxidation resistance of Pt/Co sites. O–PtCo@Pt exhibits high mass activity (MA, 0.53 A mgPt−1) and specific activity (SA, 1.17 mA cm−2). It exhibits remarkable as cathodic catalyst in proton exchange membrane fuel cells. It achieves power density of 1.14 W cm−2 at 2.0 A cm−2, with MA of 0.50 A mgPt−1 at 0.9 V. It maintains stability with only 8 % power density loss after 30,000 cycles, retaining MA of 0.35 A mgPt−1.

Immobilizing ultrafine PtRu alloy nanoparticles onto 3D interconnected MXene-graphene frameworks for highly efficient methanol oxidation

Although direct methanol fuel cell (DMFC) is regarded as a promising power source to establish green energy conversion system, its overall performance is largely limited by the slow methanol oxidation kinetics of current anode catalysts. Herein, we demonstrate a robust and facile bottom-up strategy for the controllable construction of ultrafine PtRu alloy nanoparticles immobilized onto three-dimensional (3D) interconnected Ti3C2Tx MXene-graphene frameworks (PtRu/MXene-G) through a co-assembly process. Interestingly, the utilization of 3D porous MXene-G matrix provides strong interfacial interactions with alloy nanocrystals and promotes the transportation of both reactant and electron during the electrocatalytic process, while the introduction of Ru atoms ameliorates the Pt electronic structure and generates plentiful hydroxyl species for the oxidative removal of CO byproducts. Working together, the resulting PtRu/MXene-G nanoarchitecture with an appropriate Pt/Ru atomic ratio exhibits exceptional methanol oxidation properties in terms of a large electrochemically active surface area of 101.8 m2 g−1, a high mass (specific) activity of 1779.5 mA mg−1 (1.75 mA cm−2), and good long-term stability, all of which are significantly superior to those of conventional Pt/carbon black, Pt/G, Pt/MXene, and Pt/MXene-G catalysts with an identical Pt usage.

Strong Metal‐Support Interactions in ZrO2‐Supported IrOx Catalyst for Efficient Oxygen Evolution Reaction

AbstractThe use of ZrO2 as a support material for IrOx‐based catalysts in oxygen evolution reaction (OER) electrocatalysis was studied using ex‐situ characterization and rotating disk electrode electrochemical testing of supported IrxZr(1‐x)O2 on ZrO2 of varying sizes. The catalyst exhibited high OER mass (specific) activity (712 A ) and intrinsic activity (4.8 mA ) at 1.6 VRHE, attributed to IrxZr(1‐x)O2 alloy formation, an interconnected network of Irx Zr(1‐x)O2 nanoparticles and the presence of Ir(III)/Ir(IV) species throughout the bulk. It also appears to be resistant to Ir dissolution; however, accumulation of O2 bubbles in the catalyst microstructure and minor phase transformation of Ir(III)/Ir(IV) species during OER cause deactivation. Temperature‐programmed desorption indicated a possible link between the observed high activity and higher amounts of adsorbed H2O and desorbed O2 species.

Modulation of iron-based perovskites for enhanced electrocatalytic oxygen evolution reaction by a multi-method approach

Perovskite oxides have been a hot topic of research in the field of water electrolysis due to their tunable construction; however, the poor conductivity and insufficient electrocatalytic activity of extensively studied iron-based perovskites have hindered their widespread availability. While most reported schemes focus on a stand-alone measure to modulate the physicochemical properties of perovskite oxides, herein, we utilize a multi-method approach to improving the parent perovskite SrFeO3-δ (SF). A novel perovskite oxide with a nominal composition of Sr0.9Fe0.6Co0.2Ni0.2O3-δ (S9FCN) is formulated for efficiently catalyzing oxygen evolution reaction (OER) in alkaline electrolytic water, employing the B-site co-doping with the dynamic cations Co, Ni and the A-site Sr deficiency from a highly tunable construction management to enhance the electrocatalytic activity of the targeted perovskite sample. Utilizing this concept, encouragingly, the constructed S9FCN perovskite catalyst exhibits excellent OER catalytic activity with low overpotential of 340 mV at 10 mA cm-2, high mass activity (153.32 A gcatalyst-1) and specific activity (1.91 mA cmBET-2 and 0.11 mA cmECSA-2) under a 400 mV overpotential, along with outstanding electrochemical durability without obvious degradation up to 40 h, which is much superior to that of its parent SF and stoichiometric SFCN counterparts. The improvement of electrochemical performance of iron-based perovskite catalysts by a multi-method approach stands a chance of speeding up the practical application of OER electrocatalysts.

One-pot synthesis of ultrafine trimetallic PtPdCu alloy nanoparticles decorated on carbon nanotubes for bifunctional catalysis of ethanol oxidation and oxygen reduction

Bifunctional catalysts for ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) with high noble-metal utilization are highly beneficial to direct ethanol fuel cells (DEFCs). This study developed a ternary bifunctional catalyst composed of ultrafine PtPdCu alloy nanoparticles and carbon nanotubes (CNTs) support through a facile surfactant-free solvothermal route. The carboxyl terminal groups on CNTs ensure the confined growth of PtPdCu alloys (∼5 nm) and suppress Ostwald ripening of metallic active sites during electrochemical cycling. Consequently, PtPdCu/CNTs exhibits high mass activity (1.95 A mg−1) and specific activity (4.08 mA cm−2) toward EOR, which are 7.8 and 8.9 times higher, respectively, than those of commercial Pt/C. Furthermore, PtPdCu/CNTs displays superior stability toward EOR compared with its bimetallic counterparts (PtPd/CNTs and PtCu/CNTs). In addition, PtPdCu/CNTs exhibits the highest half-wave potential of 0.888 V among all electrocatalysts, indicating high ORR activity. Density functional theory calculations reveal that Pd and Cu mediate the electronic structure of Pt, leading to enhanced catalytic activity of PtPdCu/CNTs. The excellent catalytic property of PtPdCu/CNTs can also be attributed to the bifunctional effects of Pd/Cu and the interaction between metal and the carbon support. The proposed material is a contribution to the family of efficient ternary-alloy electrocatalysts for fuel cells.

Hierarchical Pt-In Nanowires for Efficient Methanol Oxidation Electrocatalysis.

Direct methanol fuel cells (DMFC) have attracted increasing research interest recently; however, their output performance is severely hindered by the sluggish kinetics of the methanol oxidation reaction (MOR) at the anode. Herein, unique hierarchical Pt-In NWs with uneven surface and abundant high-index facets are developed as efficient MOR electrocatalysts in acidic electrolytes. The developed hierarchical Pt89In11 NWs exhibit high MOR mass activity and specific activity of 1.42 A mgPt-1 and 6.2 mA cm-2, which are 5.2 and 14.4 times those of Pt/C, respectively, outperforming most of the reported MORs. In chronoamperometry tests, the hierarchical Pt89In11 NWs demonstrate a longer half-life time than Pt/C, suggesting the better CO tolerance of Pt89In11 NWs. After stability, the MOR activity can be recovered by cycling. XPS, CV measurement and CO stripping voltammetry measurements demonstrate that the outstanding catalytic activity may be attributed to the facile removal of CO due to the presence of In site-adsorbing hydroxyl species.

IrO2 Nanoparticle-Decorated Ir-Doped W18O49 Nanowires with High Mass Specific OER Activity for Proton Exchange Membrane Electrolysis.

The oxygen evolution reaction (OER) severely limits the efficiency of proton exchange membrane (PEM) electrolyzers due to slow reaction kinetics. IrO2 is currently a commonly used anode catalyst, but its large-scale application is limited due to its high price and scarce reserves. Herein, we reported a practical strategy to construct an acid OER catalyst where Iridium oxide loading and iridium element bulk doping are realized on the surface and inside of W18O49 nanowires by immersion adsorption, respectively. Specifically, W0.7Ir0.3Oy has an overpotential of 278 mV at 10 mA·cm-2 in 0.1 M HClO4. The mass activity of 714.10 A·gIr-1 at 1.53 V vs. the reversible hydrogen electrode (RHE) is 80 times that of IrO2, and it can run stably for 55 h. In the PEM water electrolyzer device, its mass activity reaches 3563.63 A·gIr-1 at the cell voltage of 2.0 V. This improved catalytic performance is attributed to the following aspects: (1) The electron transport between iridium and tungsten effectively improves the electronic structure of the catalyst; (2) the introduction of iridium into W18O49 by means of elemental bulk doping and nanoparticles supporting for the enhanced conductivity and electrochemically active surface area of the catalyst, resulting in extensive exposure of active sites and increased intrinsic activity; and (3) during the OER process, partial iridium elements in the bulk phase are precipitated, and iridium oxide is formed on the surface to maintain stable activity. This work provides a new idea for designing oxygen evolution catalysts with low iridium content for practical application in PEM electrolyzers.

Dendritic Ag Electrocatalyst with High Mass-Specific Activity for Zero-Gap Gas-Fed CO2 Electroreduction

Dendritic Ag Electrocatalyst with High Mass-Specific Activity for Zero-Gap Gas-Fed CO₂ Electroreduction

Exploring the Function of Nitrogen-Doped Carbon Shell on Ordered and Disordered PtCo Alloy Catalysts in Oxygen Reduction Reaction By X-Ray Absorption Spectroscopy

The development of proton exchange membrane fuel cells (PEMFCs) has received increasing attention for its potential to get rid of dependence on fossil fuels and curb carbon emissions[1]. However, the application of PEMFC has been limited by the consumption of platinum due to the sluggish kinetics of the cathode reaction and limiting platinum reserves. So far, forming Pt-M (M = non-precious metal) alloying phase catalysts has been regarded as an efficient method to improve the activity and decrease the cost of platinum. However, the introduction of the non-precious metal content will decrease the stability of the catalysts by accelerating the dissolution of metal atoms and agglomeration of the nanoparticles[2]. In this research, the nitrogen-doped carbon coating structure was applied to protect the PtCo nanoparticles. And both ordered (I-PtCo@CNx) and disordered (D-PtCo@CNx) PtCo alloy phase core was synthesized to further explore the role of nitrogen-doped carbon shell in improving the activity and stability. To study the electronic statement and structure changes of the catalysts, both in-situ and ex-situ X-ray absorption spectroscopy (XAS) was applied at BL36XU at SPring-8.The synthesis of order PtCo catalysts, generally, requires a high temperature to overcome the energy barrier of forming the ordering phase, which will cause severe Ostwald ripening and get larger nanoparticles[3]. However, in the participation of nitrogen-doped carbon shells, the particle size could be limited to less than 5 nm. The I-PtCo@CNx exhibited high mass activity and specific activity at 1.08 A mgPt -1 and 1.51 mA cmPt -2, respectively. The XAS and X-ray photoelectron spectroscopy (XPS) analysis showed the decreased electronic density on the I-PtCo@CNx compared with I-PtCo catalysts, which suggested the increase of the activity might be originated from the interaction from the nitrogen-doped carbon shell. Furthermore, the accelerate durability tests (ADTs) were applied to measure the stability of the catalysts. In the rotating disk electrode and fuel cell condition, after 30,000 cycles ADTs, the activity of I-PtCo@CNx showed less decrease compared with other samples. The EXAFS analysis confirmed the high stability of I-PtCo@CNx might come from the less oxygen species generation during the ADTs, especially for the Co, and the confined structure benefits to maintaining the structure. In addition, the operando XAS analysis of the membrane electrode assemblies (MEA) samples also showed the high stability of I-PtCo@CNx after polarization at 1.1 V for 1 h. Figure 1. The Pt L3 edge and Co K edge FT-EXAFS spectra of disordered-PtCo, ordered-PtCo, and ordered-PtCo@CNx in different ADTs cycles at 80 °C in MEA operation condition. Acknowledgement This work was supported by the project (JPNP20003) and a NEDO FC-Platform project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). And China Scholarship Council (CSC) was acknowledged for the doctoral scholarship of Yunfei Gao (202006270046). Reference s : [1] Zhao L.; Zhu J.; Zheng Y.; Xiao M.; Gao R.; Zhang Z.; et al. Adv. Energy Mater. 2022, 12, 2102665.[2] Sun Y.; Polani S.; Luo F.; Ott S.; Strasser P.; Dionigi F. Nat. Commun. 2021, 12 (1), 5984.[3] Yang C.; Wang L.; Yin P.; Liu J.; Chen M.; Yan Q.; et al. Science 2021, 374 (6566), 459-64. Figure 1

Highly dispersed L12-Pt3Fe intermetallic particles supported on single atom Fe-Nx-Cy active sites for enhanced activity and durability towards oxygen reduction

Highly active and durable oxygen reduction reaction (ORR) catalysts with sufficient activity and stability of Pt are beneficial for the commercialization of proton exchange membrane fuel cells. Here we report an effective approach to prepare a composite catalyst comprising of ordered L12-Pt3Fe intermetallic nanoparticles interact with single atom Fe-Nx-Cy active sites. The addition of Fe and the confinement effect of hierarchical porous structure limit the growth of intermetallic particle size (around 2.5 nm). The ligand effect of the electron transfer from Fe to Pt and the synergistic interaction between L12-Pt3Fe and Fe-Nx-Cy work together to reduce oxygen intermediates adsorption and improve kinetics process. Experimentally, the L12-Pt3Fe/CFe-N-C catalyst shows high mass activity and specific activity at 1.010 A/mgPt and 1.166 mA/cm2, respectively, which are 5.8 and 5.1 times higher than those of commercial Pt/C (0.174 A/mgPt and 0.230 mA/cm2). Thanks to the more stable L12 structure, L12-Pt3Fe/CFe-N-C exhibits better durability (14 mV E1/2 loss of L12-Pt3Fe/CFe-N-C and 33 mV E1/2 loss of commercial Pt/C) after 30,000 cycles accelerated stress tests. The strategy to design and prepare small particle Pt-based intermetallic alloys coordinated with M-N-C active sites provides a new direction to obtain low-cost and easily prepared effective ORR catalysts.

Fabrication of Low Loading Ag Electrodes for CO2 Reduction Reaction in Zero-Gap Electrolyzer

In recent years, there has been intense effort directed towards catalyst development and electrode design for electrochemical carbon dioxide reduction reaction (CO2RR) with an objective of achieving high production rate (current density) of desirable products including CO, CH3OH, CH4 and C2+ hydrocarbons. Silver electrocatalyst is reported to exhibit remarkable CO selectivity and high current density, both of which are requisite parameters for CO2RR electrolyzer scale up. Silver is still moderately priced and reduction of Ag loading in CO2RR electrode is one of the technological goals for electrolyzer development.Most of the prior studies on Ag electrodes for CO2RR have utilized Ag nanoparticles, which are typically spray coated on a substrate from Ag or Ag-ionomer suspension resulting in high-Ag loading (> 1 mg/cm2 loading) and hence low mass specific activity (MSA) < 150 mA.mg-1 Ag. In this work, we developed a combined approach for Ag deposition using pulse electrodeposition (PE) and spray coating (SC) with an aim of decreasing Ag loading and increasing MSA. Such electrodes were found to exhibit high current densities and CO selectivity even with low Ag loading (< 0.5 mg/cm2).Specifically, several different gas diffusion electrodes (GDE) prepared by pulse electrodeposition of silver, spray coating of Ag nanoparticles, and combination of the two were prepared by coating of Sigracet gas diffusion layer (GDL). Commercial IrO2 electrode and the fabricated silver electrode were utilized as the anode and cathode, respectively. The anode and the cathode were separated by a polymer electrolyte membrane, which was Sustainion® X37-50 Grade 60- an anion exchange membrane. 10 mM KHCO3 electrolyte was re-circulated at the anode using a pump while humidified CO2 gas was flowed through the cathode. CO2RR tests are performed in a zero-gap electrolyzer setup, at a temperature of 25 °C.The main findings are summarized in the Figure below. The electrode prepared by pulse electrodeposition (PE) exhibits a low areal current density (~30 mA/cm2) but high mass-specific activity of 302 mA.mg-1 Ag. However, the selectivity for CO is low. On the other hand, spray coated (SC) electrodes yield higher CO selectivity and higher areal current density but mass specific activity is lower. By depositing silver sequentially, either pulse electrodeposition (PE) followed by spray coating (SC), i.e. the SC+PE electrode, or SC followed by PE (PE+SC electrode), both the mass-specific and areal current density increased drastically while CO selectivity remained high (99%). In particular, the current densities of the PE and SC electrodes are improved by 2 and 4.5 times, respectively, from 31 and 70 mA.cm-2 up to 136 mA.cm-2 on the SP+PE electrode, at the cell voltage of -3 V. Also, the CO selectivity of the electrodes is improved from 25 % (PE sample) and 81 % (SC sample) up to 99 % on the SC+PE electrode. The optimized electrode provided a catalyst layer with high surface coverage of silver on the GDL substrate at low Ag loadings (<0.5 mg/cm2). Further optimization of electrode is underway including modification of silver deposition and incorporation of ionomer to increase current density while maintaining the CO selectivity and durability of GDE. Details of the electrode fabrication and characterization as well as performance evaluation will be presented at the meeting. Figure 1

1D-2D hybridization: Nanoarchitectonics for grain boundary-rich platinum nanowires coupled with MXene nanosheets as efficient methanol oxidation electrocatalysts

Although a direct methanol fuel cell with high energy utilization efficiency and low hazardous emission has broad application prospects in various energy-related fields, the insufficient methanol oxidation activity as well as the short service life of the anode catalysts continue to hinder its large-scale commercialization. Herein, we demonstrate a convenient and robust approach for the controllable synthesis of 1D grain boundary-rich Pt nanowires strongly coupled with ultrathin Ti3C2Tx MXene nanosheets (Pt NWs/MX). Such a unique architectural design endows the heterojunction catalysts with a series of structural merits, including large accessible surface area, stable interconnected Pt networks, numerous grain boundary sites, ameliorative electronic structure, and excellent electron conductivity. Consequently, the optimized Pt NWs/MX catalyst exhibits a unique methanol oxidation performance with a large electrochemically active surface area of 105.5 m2 g−1, a high mass (specific) activity of 1621.5 mA mg−1 (1.6 mA cm−2), as well as superior long-term durability, making it more competitive than conventional Pt nanoparticle/carbon catalysts with the same Pt loading.

Building 3D Interconnected MoS2 Nanosheet–Graphene Networks Decorated with Rh Nanoparticles for Boosted Methanol Oxidation Reaction

The development of direct methanol fuel cell technology is one of the important ways to establish green energy production and conversion systems, while its large-scale commercial applications are severely hindered by the high cost and insufficient performance of current Pt-based anode catalysts. Here, we report the design and construction of a novel non-Pt electrocatalyst made from three-dimensional (3D) interconnected MoS2 nanosheet–reduced graphene oxide networks decorated with ultrafine Rh nanoparticles (Rh/MoS2-RGO) via a controllable co-assembly strategy. With unique structural features such as large specific surface areas, 3D interweaving porous frameworks, uniform Rh distribution, and excellent electron conductivity, the optimized Rh/MoS2-RGO catalyst is endowed with boosted electrocatalytic methanol oxidation properties, including a large electrochemical active surface area of 95.5 m2 g–1, a high mass (specific) activity of 1502.0 mA mg–1 (1.57 mA cm–2), and robust long-term stability, all of which significantly outperform those of reference Rh/RGO, Rh/carbon black, Rh/MoS2, as well as commercial Pt/carbon black and Pd/carbon black catalysts with the same metal content.

Intermetallic PdCd Core Promoting CO Tolerance of Pd Shell for Electrocatalytic Formic Acid Oxidation†

Comprehensive SummaryLiquid fed fuel cells such as direct formic acid fuel cells (DFAFCs) are considered to be promising power sources for portable electronic devices. However, the poison of CO intermediates on the state‐of‐the‐art platinum and palladium‐based electrocatalysts for the formic acid oxidation reaction (FAOR) at the anode hampers the implementation of DFAFCs technologies. Here, we report a core/shell catalyst consisting of intermetallic PdCd core and Pd shell (i‐PdCd@Pd) with promoted CO anti‐poison ability and thus FAOR performance. The optimal i‐PdCd@Pd catalyst exhibits a high mass activity and specific activity at peak potential, which are 24 and 4 times greater than that of commercial Pd/C catalyst, respectively. We understand by in‐situ surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRA) and X‐ray photoelectron spectroscopy (XPS) that in i‐PdCd@Pd, the intermetallic PdCd under‐layers can induce the downshift of d‐band center of surface Pd atoms, which would improve the CO tolerance and thus promote the FAOR performance.

Preparation Strategy Using Pre-Nucleation Coupled with In Situ Reduction for a High-Performance Catalyst towards Selective Hydrogen Production from Formic Acid

Formic acid decomposition (FAD) is one of the most promising routes for rapid hydrogen (H2) production. Extensive efforts have been taken to develop efficient catalysts, which calls for the simultaneous regulation of the electronic structure and particle size of the catalyst. The former factor determines the intrinsic performance, while the latter corresponds to the active site utilization. Here, an effective preparation strategy, pre-nucleation coupled with in situ reduction, is developed to realize and well-tune both surface electronic states and particle size of the pallidum (Pd) catalyst. Benefiting from the structural merits, the as-prepared catalyst exhibits high mass-specific activity of 8.94 molH2/(gPd·h) with few carbon monoxide (CO) molecules, and the activation energy could reach a value as small as 33.1 kJ/mol. The work not only affords a highly competitive FAD catalyst but also paves a new avenue to the synthesis of ultra-fine metal nanoparticles with tailorable electronic structures.