Nanoparticle Electrocatalysts Research Articles

Electrocatalyst‐Hydrogel Polymer Nanocomposite Thin Films for Water Splitting

AbstractRealization of scalable technologies for key processes like electrochemical water splitting requires the development of sustainable, efficient and cost‐effective catalytic electrodes. The innumerable electrocatalysts being developed in contemporary research rely on the use of a limited choice of binders for effective deployment in the electrolysis setting. Recent studies have demonstrated the utility of electrically insulating hydrogel polymers as suitable matrices for incorporating the electrocatalyst nanoparticles; the nanocomposite thin films coated on conducting substrates mediate highly efficient electrocatalytic water splitting reactions through the effective confinement of the electrolyte within and release of the gaseous products. After a brief introduction to the basic challenges in the field and the existing approaches that address them, this article outlines the promise of hydrogel based nanocomposite thin films in developing efficient and sustainable catalytic electrodes for water splitting, and their functional role in enhancing the efficiency of the electrochemical process. Directions for further development in this domain are noted.

Dual confinement of RuOx nanoparticle using polar MnNiO and armored carbon for boosting water electrolysis

The poor stability of nanoparticle catalysts with catalytic activity is a significant obstacle to their industrial application. The establishment of rational nanoparticle structures to elucidate the relationship between catalyst structure and its catalytic activity and stability is crucial for constructing nanoparticle catalysts that are both highly active and stable. We propose a strategy to construct a dual-confinement effect of the nanoparticle, specifically by regulating the polarization of the MnNiO support to enhance strong oxide-support interactions (SOSI) and encapsulating the outer layer of nanoparticles with a carbon shell, which has been proven effective in improving the activity and stability of nanoparticle-based oxygen evolution reaction (OER) electrocatalysts. At a current density of 100 mA cm−2, the armor C@RuOx@MnNiO catalyst displays an overpotential of 260 mV for the OER. After the OER test for 100 h, the current density of C@RuOx@MnNiO shows no significant decay, whereas that of RuOx@MnNiO and RuOx@MnO rapidly decreases, indicating significant catalytic activity and stability of the catalyst. The assembled C@RuOx@MnNiO||Pt/C electrode demonstrates excellent alkaline water electrolysis performance in an MEA electrolyzer, requiring only a low cell voltage of 1.76 V to achieve an ampere-level current density of 1 A cm−2. In-situ electrochemical Raman spectroscopy reveals the significant interaction between nanoparticles and the polar support. The reduction in Gibbs free energy, which establishes the rate-determining step (RDS) of OER, is caused by the charge redistribution caused by polar Mn doping in RuOx@MnNiO and the coordination structure modifications, as shown by density functional theory calculations. This work provides an approach to designing efficient and stable nanoparticle electrocatalysts through the dual-confinement effect of SOSI-induced strong interactions and armor carbon layers.

Electrochemical Plasma-Activated CO2 Reduction at a Plasma-Water Interface

The development of technologies and processes to decarbonize chemical and fuel production is key to reducing global anthropogenic greenhouse gas emissions. Electrochemical carbon dioxide reduction enables a sustainable pathway to circularize carbon-based chemical products by upgrading recovered carbon dioxide using renewable energy sources. Electrochemical CO2 reduction has successfully been employed to produce chemicals such as methanol and ethylene, but it has been hindered by dependence on elevated temperature to achieve high yields and limited ability to generate higher order carbon products. Non-thermal carbon dioxide plasma can be generated at ambient temperature and pressure and contains energetically excited oxygen and carbon species. When introduced to an electrocatalyst, these reactive species could more readily participate in reaction pathways with higher activation barriers towards forming higher order carbon species compared to electrochemical reactions involving ground-state reactants. Further, plasma discharges over water in an electrochemical cell generate plasma-activated water, introducing solvated electrons and secondary reactive oxygen species.In this work, we investigate how the use of plasma-activated carbon dioxide and a plasma-water interface impacts electrochemical product generation. We design a novel non-thermal plasma electrode to discharge carbon dioxide plasma into water in an electrochemical cell with a Cu nanoparticle electrocatalyst. Results suggest the potential for a plasma-water electrochemical system to generate value-added products that are less commonly generated in electrochemical processes at ambient pressure and temperature.

Stabilization of Metal Alloy Nanocatalysts by Encapsulation with a Metal Oxide

The threat of climate change motivates us to reduce our reliance on fossil fuels and transition to renewable energy infrastructure. Many clean energy technologies including hydrogen fuel cells, direct methanol fuel cells, and water electrolyzers utilize electrocatalysts to generate electricity from chemical energy or vice versa. One direction for increasing the catalytic performance and tolerance to contaminants of the catalyst layers is the development of metal alloy-based catalysts. For instance, ruthenium (Ru) can be alloyed with platinum (Pt) to increase the tolerance of Pt to carbon monoxide, a contaminant that can be found in hydrogen fuel. However, metal alloy catalysts have an additional route for degradation beyond the well-established Ostwald ripening, coalescence, and dissolution mechanisms that are an issue for nanoparticle electrocatalysts. Harsh fuel cell conditions can lead to a separation of the two metals that were originally alloyed in the nanocatalyst and, as a result, this leads to a loss in catalytic performance and tolerance to contaminants.1 This project focuses on the durability of alloyed PtRu electrocatalysts, which facilitate the methanol oxidation reaction in a direct methanol fuel cell and the hydrogen oxidation reaction in a hydrogen fuel cell.This project explored an encapsulation of electrodeposited PtRu nanoparticle catalysts with a porous niobium oxide as a method to stabilize the PtRu alloy. Niobium oxide was chosen due to its high corrosion resistance and previous studies showing its stabilization of Ru.2 PtRu alloyed nanoparticles were synthesized via electrodeposition on a glassy carbon electrode substrate and subsequently encapsulated by an electrophoretic deposition method adapted from Jha et al.3 The morphology and composition of the catalyst and encapsulating layer were characterized by scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and optical microscopy. The activity and durability of pristine and encapsulated PtRu catalysts were evaluated by cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Carbon monoxide stripping and the double layer capacitance methods were used to study changes in the electrochemically active surface area before and after deposition of the niobium oxide. Access to the electrocatalyst surfaces through the encapsulating layer was maximized by the addition of surfactants and through tuning the potentials applied during the deposition of the niobium oxide as a means to improve its porosity. The niobium oxide was shown to improve the stability of the PtRu alloy and maintain the CO tolerance of the alloy well beyond that of the un-encapsulated catalyst. The stabilization of PtRu imparted by the encapsulation of niobium oxide herein is promising for the stabilization of alloyed nanoparticle catalysts towards a wide range of electrocatalytic applications. Yang, Z.; Yu, X.; Zhang, Q. RSC Adv., 2016, 6, 114014-114018.Jha, G.; Tran, T.; Qiao, S.; Ziegler, J. M.; Ogata, A. F.; Dai, S.; Xu, M.; Thai, M. L.; Chandran, G. T.; Pan, X.; Penner, R. M. Mater. 2018, 30, 6549-6558.

Precisely Designed Ultra-Small CoP Nanoparticles-Decorated Hollow Carbon Nanospheres as Highly Efficient Host in Lithium-Sulfur Batteries.

Designing porous carbon materials with metal phosphides as host materials holds promise for enhancing the cyclability and durability of lithium-sulfur (Li-S) batteries by mitigating sulfur poisoning and exhibiting high electrocatalytic activity. Nevertheless, it is urgent to precisely control the size of metal phosphides to further optimize the polysulfide conversion reaction kinetics of Li-S batteries. Herein, a subtlety regulation strategy was proposed to obtain ultra-small CoP nanoparticles-decorated hollow carbon nanospheres (CoP@C) by using spherical polyelectrolyte brush (SPB) as the template with stabilizing assistance from polydopamine coating, which also works as carbon source. Leveraging the electrostatic interaction between SPB and Co2+, ultra-small Co particles with sizes measuring 5.5±2.6 nm were endowed after calcination. Subsequently, through a gas-solid phosphating process, these Co particles were converted into CoP nanoparticles with significantly finer sizes (7.1±3.1 nm) compared to state-of-the-art approaches. By uniformly distributing the electrocatalyst nanoparticles on hollow carbon nanospheres, CoP@C facilitated the acceleration of Li-ion diffusion and enhanced the conversion reaction kinetics of polysulfides through adsorption-diffusion synergy. As a result, Li-S batteries utilizing the CoP@C/S cathode demonstrated an initial specific discharge capacity of 850.0 mAh g-1 at 1.0 C, with a low-capacity decay rate of 0.03 % per cycle.

Investigation on borohydride oxidation performance of activated charcol supported palladium-bismuth nanoparticles electrocatalyst for fuel cell application

Investigation on borohydride oxidation performance of activated charcol supported palladium-bismuth nanoparticles electrocatalyst for fuel cell application

Synergistic impact of dual active sites in Nb-Fe2P nanoparticles on electrocatalytic nitrate reduction with high selectivity

The electrochemical transformation of nitrate into ammonia offers a promising alternative to the traditional Haber-Bosch process. The nitrate reduction reaction (NO3–RR) involves complex multi-electron/proton processes and faces competition from hydrogen evolution reactions, leading to low Faraday efficiency and diminished ammonia production. This study introduces carbon-supported niobium-doped iron phosphide nanoparticles (Nb-Fe2P) electrocatalysts, synthesized using deep eutectic solvent (DES). These electrocatalysts achieved an exceptional ammonia yield of 9.7 mg h−1 cm−2 and a Faraday efficiency of 95.8 % in the NO3–RR. Both experimental and theoretical studies reveal that the dual active sites of Fe and Nb significantly enhance the generation of active hydrogen and expedite the utilization of nitrogen-containing intermediates. This innovative approach, focusing on active hydrogen balance, offers a strategic pathway for developing highly efficient NO3–RR electrocatalysts by promoting the dissociation of H2O.

Tailored porous triazine-based organic frameworks decorated with gold nanoparticles: A robust platform for ultra-sensitive arsenite detection

An effective electrochemical sensing platform for As(III) determination was developed through in situ growing gold nanoparticles electrocatalyst inside the highly microporous melamine-based chemical organic framework (N-POP) with a large surface area prepared through the catalyst-free polycondensation between melamine and terephthalaldehyde. The microporous structure afforded support for the synchronous anchoring of more gold nanoparticles and exposing abundant unsaturated active sites for highly sensitive As(III) detection. The optimized synthesis was characterized by FT-IR, SEM, HR-TEM, UV–Vis, and XPS successful formation of the polymer, and the morphologically favorable heterojunction between AuNPs and the N-POP gave rise to enhanced electrochemical responses toward As(III) determination. Several parameters related to the synthesis of the nanocomposite and instrumental parameters were optimized to achieve the best performance of the sensor. Under optimized conditions, the electrode exhibits enhanced electrochemical performance toward As(III) without noticeable interference from other commonly coexisting ions on the determination of As(III). Additionally, robust stability and reproducibility were achieved for the electrodes. While this work forms the basis for further progress on nanomaterials-coated COFs, As(III) detection in different water samples was successfully demonstrated here.

Approaching high rate All-Solid-State Lithium-Sulfur batteries via promoted sulfur conversion with nickel oxide nanoparticle electrocatalyst

All-solid-state lithium-sulfur battery (ASLSB) is deemed a promising next-generation energy storage device owing to its combination of high theoretical specific energy (2600 Wh kg−1) derived from the sulfur active material, and exceptional safety characteristics and the ability to suppress the polysulfide shuttle effect through the use of solid electrolyte (SE). However, the low electronic and ionic conductivity of sulfur, coupled with the poor solid–solid interfacial contact inherent in all-solid-state configuration, has resulted in poor electrochemical performance. Herein, NiO electrocatalyst supported on N-doped sites of super-p was synthesized and incorporated as a carbon additive in the composite cathode of the ASLSB. The direct growth of nanosized NiO electrocatalyst on the N-doped sites of super-p ensures facile electron transfer to the electrocatalyst surface, while maximizing the electrocatalyst’s surface area. As a result, the overpotential during charging and discharging of the ASLSB was significantly reduced, as assessed through galvanostatic intermittent titration technique and cyclic voltammetry, indicating enhanced redox conversion of sulfur. Furthermore, the Li6PS5Cl sulfide SE induces solid–solid conversion of sulfur, eliminating the dissolution issue of polysulfide intermediates and ensuring good cycle performance. The assembled ASLSB exhibits a high reversible capacity of 1845 mAh g−1 at 0.05C at room temperature and enhanced rate capability at high C-rates, operated at 60 °C. Even at a substantially high sulfur loading level of 6.65 mg cm−2, a maximum areal capacity of 9.48 mAh cm−2 was achieved at room temperature, highlighting the important role of electrocatalyst in realizing high performance ASLSBs.

Importance of Site Diversity and Connectivity in Electrochemical CO Reduction on Cu.

Electrochemical CO2 reduction on Cu is a promising approach to produce value-added chemicals using renewable feedstocks, yet various Cu preparations have led to differences in activity and selectivity toward single and multicarbon products. Here, we find, surprisingly, that the effective catalytic activity toward ethylene improves when there is a larger fraction of less active sites acting as reservoirs of *CO on the surface of Cu nanoparticle electrocatalysts. In an adaptation of chemical transient kinetics to electrocatalysis, we measure the dynamic response of a gas diffusion electrode (GDE) cell when the feed gas is abruptly switched between Ar (inert) and CO. When switching from Ar to CO, CO reduction (COR) begins promptly, but when switching from CO to Ar, COR can be maintained for several seconds (delay time) despite the absence of the CO reactant in the gas phase. A three-site microkinetic model captures the observed dynamic behavior and shows that Cu catalysts exhibiting delay times have a less active *CO reservoir that exhibits fast diffusion to active sites. The observed delay times and the estimated *CO reservoir sizes are affected by catalyst preparation, applied potential, and microenvironment (electrolyte cation identity, electrolyte pH, and CO partial pressure). Notably, we estimate that the *CO reservoir surface coverage can be as high as 88 ± 7% on oxide-derived Cu (OD-Cu) at high overpotentials (-1.52 V vs SHE) and this increases in reservoir coverage coincide with increased turnover frequencies to ethylene. We also estimate that *CO can travel substantial distances (up to 10s of nm) prior to desorption or reaction. It appears that active C-C coupling sites by themselves do not control selectivity to C2+ products in electrochemical COR; the supply of CO to those sites is also a crucial factor. More generally, the overall activity of Cu electrocatalysts cannot be approximated from linear combinations of individual site activities. Future designs must consider the diversity of the catalyst network and account for intersite transportation pathways.

Oxygen Reduction Pathway for Spinel Metal Oxides in Alkaline Media: An Experimentally Supported Ab Initio Study.

Precious-metal-free spinel oxide electrocatalysts are promising candidates for catalyzing the oxygen reduction reaction (ORR) in alkaline fuel cells. In this theory-driven study, we use joint density functional theory (JDFT) in tandem with supporting electrochemical measurements to identify a novel theoretical pathway for the ORR on cubic Co3O4 nanoparticle electrocatalysts, which aligns more closely with experimental results than previous models. The new pathway employs the cracked adsorbates *(OH)(O) and *(OH)(OH), which, through hydrogen bonding, induce spectator surface *H. This results in an onset potential closely matching experimental values, in stark contrast to the traditional ORR pathway, which keeps adsorbates intact and overestimates the onset potential by 0.7 V. Finally, we introduce electrochemical strain spectroscopy (ESS), a groundbreaking strain analysis technique. ESS combines ab initio calculations with experimental measurements to validate the proposed reaction pathways and pinpoint rate-limiting steps.

Synthetic design of active and stable bimetallic PtTi nanoparticle electrocatalysts for efficient oxygen reduction at fuel cell cathodes

We explore and utilize correlations between wet-chemical synthesis parameters and the resulting atomic geometry and crystal phase structure of carbon-supported bimetallic PtTi/C alloy nanoparticles with excellent electrocatalytic reactivity for and...

Synthesis of FeCoNiCuPt high-entropy alloy nanoparticle electrocatalysts with various Pt contents by a solid-state reaction method

FeCoNiCuPt high-entropy alloy nanoparticles with small sizes (3–7 nm) and different Pt contents have been successfully synthesized by a facile solid-state reaction method.

In situ preparation of cobalt@N-doped porous carbon bifunctional electrocatalyst for efficient overall water splitting

Developing highly efficient noble-metal-free bifunctional nanocatalysts for electrocatalytic water splitting is attractive but challenging. Notably, the rational structure engineering could effectively promote electronic transfer and improve the active area. Herein, a free-standing N-doped porous carbon nanosheet arrays encapsulated with metallic Co nanoparticles electrocatalyst (Co@NC-A) for overall water splitting was designed via pyrolysis process followed with acid treatment. The N-doped carbon matrix not only enhances electron mobility and protects the metallic Co nanoparticles from electrolyte corrosion, but also improves the electrochemically active area and facilitates mass transfer. Consequently, the Co@NC-A exhibits superior electrocatalytic performance toward OER (η10 = 270 mV) and HER (η10 = 162 mV) in 1 M KOH. Moreover, the Co@NC-A as a bifunctional catalyst in overall water splitting could approach 10 mA cm−2 at a cell voltage of 1.66 V and operate stably for 50 h. Combined with the density functional theory (DFT) calculations, the improvement of the HER and OER activities is also attributed to the modified electronic structure with N-doped carbon and the optimized free energy toward the adsorption/desorption of intermediates. This work provides a novel and facile non-precious metal catalyst for water splitting and should be instructive for designing more carbon-based nanocatalysts.

(Invited) Coupling of Electrochemistry with Surface Science and Computational Modeling to Understand Nanoparticle Electrocatalysts

We investigated nanoparticle electrocatalysts in oxygen evolution reaction (OER) and CO2 reduction reaction (CO2RR) via an approach coupling electrochemistry with ultra-high vacuum (UHV) surface science and computational modeling. Well-defined nanoparticle electrocatalysts such as Fe2O3, NiFeOx, and Ag, were prepared in the UHV chamber via physical vapor deposition (PVD) and characterized with surface science techniques including X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), followed by electrochemistry measurements to establish the structure-property relationships in OER and CO2RR. Calculations based on density functional theory (DFT) and microkinetic modeling (MKM) were then implemented to gain fundamental insight into these systems. We observed the edge-enhanced OER activity of Au-supported, ultra-thin Fe2O3 electrocatalysts and revealed incorporation of Ni at the edge sites (NiFeOx) further boosting their OER activity. We also resolved the size-dependent transition between CO2RR and H2 evolution reaction (HER) selectivity in sub-5 nm Ag electrocatalysts and identified an effective minimum size limit of ∼4 nm for active and selective Ag catalysts: particle diameters below this range experienced increased H2 evolutions due to a high population of Ag edge sites; and larger diameter particles favored CO2RR as the population of Ag(100) surface sites grew but will begin to lose catalyst utilization based on total metal masses.

Probing the Effect of Environments on the Stability of Ni2P Nanoparticle Electrocatalysts

Ni2P has been shown to be an effective catalyst for the hydrogen evolution reaction (HER), making it a promising replacement for Pt which is the current state of the art HER catalyst.1,2 H2 is a clean-energy critical fuel and chemical highlighted by the US Department of Energy’s “Hydrogen Shot,” which seeks to reduce “the cost of carbon-neutral hydrogen by 80% to $1 per 1 kg in 1 decade, highlighting the key role of hydrogen in implementing carbon-neutral solutions.”3 Ni2P is also a good or promising catalyst for other reactions, such as alcohol oxidation, hydrodesulfurization,4,5 nitrate reduction, and oxygen evolution reaction.6 However, Ni2P and other TMPs are susceptible to oxidation, which can lead to catalyst degradation and loss in certain conditions.7,8 Stability is an important part of catalysis, especially for achieving the goals of the Hydrogen Shot. Therefore, it is important to understand complex degradation mechanisms in order to better understand structure-activity relationships in these materials. In the present work, in situ Ni K-edge X-ray absorption spectroscopy (XAS) and ex situ P Kα and Kβ X-ray emission spectroscopy (XES) couple together to understand the degradation of Ni2P and show the effects of electrolyte pH, ligands, and air on Ni2P nanoparticles.5 nm Ni2P nanoparticles were synthesized by heating NiCl2 and tris(diethylamino)phosphine in oleylamine. The nanoparticles were drop cast onto carbon fiber paper electrodes and Si wafers or Au-coated wafers for P Kα and Kβ XES. Oleylamine ligands are removed by thermal annealing. Electrochemical experiments were conducted with a three-electrode cell using carbon fiber paper or Au-coated wafers deposited with Ni2P nanoparticles as working electrode, Ag/AgCl calibrated to the H2 redox couple as reference electrode, and graphite rod as counter electrode. P Kα and Kβ XES experiments were conducted inside a N2 glovebox to prevent unintentional air oxidation. Transmission-mode Ni K-edge XAS was conducted on a benchtop spectrometer.Upon exposure to air, as-synthesized Ni2P nanoparticles were studied via P Kα and Kβ XES. Results showed that the phosphide species converted to phosphate with analysis of intermediates well fit by a simple two-phase mixture. Phosphide:phosphate ratios were quantified using linear combination analysis, providing a powerful tool to analyze P speciation on various samples in an inert environment and with minimal loss of material, both advantages of this system over 31P magic angle spinning solid state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. Continued work looks at analyzing the effects of the ligand environment on the stability of nanoparticles in electrolytes spanning from acidic to basic pH. We hypothesize that ligands will significantly stabilize the nanoparticles against corrosion and that without ligands Ni2P readily converts to a nickel phosphate species upon exposure to electrolyte.References(1) Popczun, E. J.; McKone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.; Schaak, R. E. Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2013, 135 (25), 9267–9270. https://doi.org/10.1021/ja403440e.(2) Liu, P.; Rodriguez, J. A. Catalysts for Hydrogen Evolution from the [NiFe] Hydrogenase to the Ni2P(001) Surface: The Importance of Ensemble Effect. J. Am. Chem. Soc. 2005, 127 (42), 14871–14878. https://doi.org/10.1021/ja0540019.(3) Bullock, M.; More, K. Basic Energy Sciences Roundtable: Foundational Science for Carbon-Neutral Hydrogen Technologies (Report); DOESC Office of Basic Energy Sciences, 2022. https://doi.org/10.2172/1834317.(4) Layan Savithra, G. H.; Muthuswamy, E.; Bowker, R. H.; Carrillo, B. A.; Bussell, M. E.; Brock, S. L. Rational Design of Nickel Phosphide Hydrodesulfurization Catalysts: Controlling Particle Size and Preventing Sintering. Chem. Mater. 2013, 25 (6), 825–833. https://doi.org/10.1021/cm302680j.(5) Rodriguez, J. A.; Kim, J.-Y.; Hanson, J. C.; Sawhill, S. J.; Bussell, M. E. Physical and Chemical Properties of MoP, Ni2P, and MoNiP Hydrodesulfurization Catalysts: Time-Resolved X-Ray Diffraction, Density Functional, and Hydrodesulfurization Activity Studies. J. Phys. Chem. B 2003, 107 (26), 6276–6285. https://doi.org/10.1021/jp022639q.(6) Menezes, P. W.; Indra, A.; Das, C.; Walter, C.; Göbel, C.; Gutkin, V.; Schmeiβer, D.; Driess, M. Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splitting. ACS Catal. 2017, 7 (1), 103–109. https://doi.org/10.1021/acscatal.6b02666.(7) Ha, D.-H.; Han, B.; Risch, M.; Giordano, L.; Yao, K. P. C.; Karayaylali, P.; Shao-Horn, Y. Activity and Stability of Cobalt Phosphides for Hydrogen Evolution upon Water Splitting. Nano Energy 2016, 29, 37–45. https://doi.org/10.1016/j.nanoen.2016.04.034.(8) Parra-Puerto, A.; Ng, K. L.; Fahy, K.; Goode, A. E.; Ryan, M. P.; Kucernak, A. Supported Transition Metal Phosphides: Activity Survey for HER, ORR, OER, and Corrosion Resistance in Acid and Alkaline Electrolytes. ACS Catal. 2019, 11515–11529. https://doi.org/10.1021/acscatal.9b03359.

TiO2-carbon supported platinum electrocatalysts for oxygen reduction reaction: Synthesis, high activity and enhanced durability

Challenges still remain in catalysts cost, activity and durability for the commercialization of polymer electrolyte membrane (PEM) fuel cells. To preferably alleviate the durability problems with carbon corrosion (but secondarily not to compromise any activities), here we demonstrate composites supported Pt nanoparticles electrocatalysts (Pt/WPx-C4-x) for oxygen reduction reaction (ORR). Of interest the composite of warm plasma-synthesized TiO2 (WP, lab-made) and Vulcan® carbon, was used to support Pt nanoparticles using a simple ethylene glycol reduction method. In terms of physicochemical structures and properties, complimentary characterizations (e.g., SEM, TEM-EDX, XRD, XPS, EPR) and the electrochemical measurements have been conducted. This composite support definitely contributes to the uniform dispersion on surface and the electronic reconfiguration of Pt nanoparticles. Our Pt/WP1–C3 catalyst has an ultrasmall Pt size (ca. 2.15 nm), and surprisingly outperforms commercial Pt/C catalyst. It has achieved 1.24 times electrochemical active surface area (ECSA), 1.85 times mass activity, and 1.5 times specific activity, compared to commercial Pt/C. More importantly, our synthesized catalysts with WP exhibited almost half the activities losses (in ECSA, mass activity, specific activity) after accelerated stress test (AST, a DOE protocol) compared to Pt/C and commercial Pt/C catalysts. Based on the extraordinary achievements on both high activity and enhanced durability, it is attributed to the synergistic effect of WP (of strong metal support interaction, oxygen vacancies, corrosion resistance), and carbon (of high surface area, electrical conductivity).

Breaking the Limit of Size-Dependent CO2RR Selectivity in Silver Nanoparticle Electrocatalysts through Electronic Metal–Carbon Interactions

Breaking the Limit of Size-Dependent CO₂RR Selectivity in Silver Nanoparticle Electrocatalysts through Electronic Metal–Carbon Interactions

Exploring the impact of Nafion modifier on electrocatalytic CO2 reduction over Cu catalyst

Nafion as a universal polymer ionomer was widely applied for nanocatalysts electrode preparation. However, the effect of Nafion on electrocatalytic performance was often overlooked, especially for CO2 electrolysis. Herein, the key roles of Nafion for CO2RR were systematically studied on Cu nanoparticles (NPs) electrocatalyst. We found that Nafion modifier not only inhibit hydrogen evolution reaction (HER) by decreasing the accessibility of H2O from electrolyte to Cu NPs, and increase the CO2 concentration at electrocatalyst interface for enhancing the CO2 mass transfer process, but also activate CO2 molecule by Lewis acid-base interaction between Nafion and CO2 to accelerate the formation of *CO, which favor of C–C coupling for boosting C2 product generation. Owing to these features, the HER selectivity was suppressed from 40.6% to 16.8% on optimal Cu@Nafion electrode at −1.2 V versus reversible hydrogen electrode (RHE), and as high as 73.5% faradaic efficiencies (FEs) of C2 products were achieved at the same applied potential, which was 2.6 times higher than that on bare Cu electrode (∼28.3%). In addition, Nafion also contributed to the long-term stability by hinder Cu NPs morphology reconstruction. Thus, this work provides insights into the impact of Nafion on electrocatalytic CO2RR performance.

Cascade electrocatalysis via AgCu single-atom alloy and Ag nanoparticles in CO2 electroreduction toward multicarbon products

Electrocatalytic CO2 reduction into value-added multicarbon products offers a means to close the anthropogenic carbon cycle using renewable electricity. However, the unsatisfactory catalytic selectivity for multicarbon products severely hinders the practical application of this technology. In this paper, we report a cascade AgCu single-atom and nanoparticle electrocatalyst, in which Ag nanoparticles produce CO and AgCu single-atom alloys promote C-C coupling kinetics. As a result, a Faradaic efficiency (FE) of 94 ± 4% toward multicarbon products is achieved with the as-prepared AgCu single-atom and nanoparticle catalyst under ~720 mA cm−2 working current density at −0.65 V in a flow cell with alkaline electrolyte. Density functional theory calculations further demonstrate that the high multicarbon product selectivity results from cooperation between AgCu single-atom alloys and Ag nanoparticles, wherein the Ag single-atom doping of Cu nanoparticles increases the adsorption energy of *CO on Cu sites due to the asymmetric bonding of the Cu atom to the adjacent Ag atom with a compressive strain.