Electrocatalyst System Research Articles

Breaking the Passivation Effect for MnO2 Catalysts in Li−S Batteries by Anion‐Cation Doping

AbstractTransition metal oxides (TMOs) are recognized as high‐efficiency electrocatalyst systems for restraining the shuttle effect in lithium‐sulfur (Li−S) batteries, owing to their robust adsorption capabilities for polysulfides. However, the sluggish catalytic conversion of Li2S redox and severe passivation effect of TMOs exacerbate polysulfide shuttling and reduce the cyclability of Li−S batteries, which significantly hinders the development of TMOs electrocatalysts. Here, through the anion‐cation doping approach, dual incorporation of phosphorus and molybdenum into MnO2 (P,Mo‐MnO2) was engineered, demonstrating effective mitigation of the passivation effect and allowing for the simultaneous immobilization of polysulfides and rapid redox kinetics of Li2S. Both experimental and theoretical investigations reveal the pivotal role of dopants in fine‐tuning the d‐band center and optimizing the electronic structure of MnO2. Furthermore, this well‐designed configuration processes catalytic selectivity. Specifically, P‐doping expedites rapid Li2S nucleation kinetics by minimizing reaction‐free energy, while Mo‐doping facilitates robust Li2S dissolution kinetics by mitigating decomposition barriers. This dual‐doping approach equips P,Mo‐MnO2 with robust bi‐directional catalytic activity, effectively overcoming passivation effect and suppressing the notorious shuttle effect. Consequently, Li−S batteries incorporating P,Mo‐MnO2‐based separators demonstrate favorable performance than pristine TMOs. This design offers rational viewpoint for the development of catalytic materials with superior bi‐directional sulfur electrocatalytic in Li−S batteries.

Breaking the Passivation Effect for MnO2 Catalysts in Li-S Batteries by Anion-Cation Doping.

Transition metal oxides (TMOs) are recognized as high-efficiency electrocatalyst systems for restraining the shuttle effect in lithium-sulfur (Li-S) batteries, owing to their robust adsorption capabilities for polysulfides. However, the sluggish catalytic conversion of Li2S redox and severe passivation effect of TMOs exacerbate polysulfide shuttling and reduce the cyclability of Li-S batteries, which significantly hinders the development of TMOs electrocatalysts. Here, through the anion-cation doping approach, dual incorporation of phosphorus and molybdenum into MnO2 (P,Mo-MnO2) was engineered, demonstrating effective mitigation of the passivation effect and allowing for the simultaneous immobilization of polysulfides and rapid redox kinetics of Li2S. Both experimental and theoretical investigations reveal the pivotal role of dopants in fine-tuning the d-band center and optimizing the electronic structure of MnO2. Furthermore, this well-designed configuration processes catalytic selectivity. Specifically, P-doping expedites rapid Li2S nucleation kinetics by minimizing reaction-free energy, while Mo-doping facilitates robust Li2S dissolution kinetics by mitigating decomposition barriers. This dual-doping approach equips P,Mo-MnO2 with robust bi-directional catalytic activity, effectively overcoming passivation effect and suppressing the notorious shuttle effect. Consequently, Li-S batteries incorporating P,Mo-MnO2-based separators demonstrate favorable performance than pristine TMOs. This design offers rational viewpoint for the development of catalytic materials with superior bi-directional sulfur electrocatalytic in Li-S batteries.

Charge Transfer in n-FeO and p-α-Fe2O3 Nanoparticles for Efficient Hydrogen and Oxygen Evolution Reaction.

This study aims to explore the n-FeO and p-α-Fe2O3 semiconductor nanoparticles in hydrogen (HER) and oxygen (OER) evolution reactions and a combined full cell electrocatalyst system to electrolyze the water. We have observed a distinct electrocatalytic performance for both HER and OER by tuning the interplay between iron oxidation states Fe2+ and Fe3+ and utilizing phase-transformed iron oxide nanoparticles (NPs). The Fe2+ rich n-FeO NPs exhibited superior HER performance compared to p-α-Fe2O3 and Fe(OH)x NPs, which is attributed to the enhancement in n-type semiconducting nature under HER potential, facilitating the electron transfer for the reduction in H+ ions. In contrast, p-α-Fe2O3 NPs demonstrated excellent OER activity. An H-cell constructed using n-FeO||p-α-Fe2O3 NPs as cathode and anode achieved a cell voltage of 1.87 V at a current density of 50 mA/cm2. The cell exhibited remarkable stability after 30 h of activation and maintained the high current density of 100 mA/cm2 for 80 h with a negligible increase in cell voltage. This work highlights the semiconducting properties of n-FeO and p-α-Fe2O3 for the electrochemical water splitting system using the band bending phenomenon under the applied potential.

Design of Cr-Based Molecular Electrocatalyst Systems for the CO2 Reduction Reaction.

ConspectusHuman influence on the climate system was recently summarized by the sixth Intergovernmental Panel on Climate Change (IPCC) Assessment Report, which noted that global surface temperatures have increased more rapidly in the last 50 years than in any other 50-year period in the last 2000 years. Elevated global surface temperatures have had detrimental impacts, including more frequent and intense extreme weather patterns like flooding, wildfires, and droughts. In order to limit greenhouse gas emissions, various climate change policies, like emissions trading schemes and carbon taxes, have been implemented in many countries. The most prevalent anthropogenic greenhouse gas emitted is carbon dioxide (CO2), which accounted for 80% of all U.S. greenhouse gas emissions in 2022. The reduction of CO2 through the use of homogeneous electrocatalysts generally follows a two-electron/two-proton pathway to produce either carbon monoxide (CO) with water (H2O) as a coproduct or formic acid (HCOOH). These reduced carbon species are relevant to industrial applications: the Fischer-Tropsch process uses CO and H2 to produce fuels and commodity chemicals, while HCOOH is an energy dense carrier for fuel cells and useful synthetic reagent. Electrochemically reducing CO2 to value-added products is a potential way to address its steadily increasing atmospheric concentrations while supplanting the use of nonrenewable petrochemical reserves through the generation of new carbon-based resources. The selective electrochemical reduction of CO2 (CO2RR) by homogeneous catalyst systems was initially achieved with late (and sometimes costly) transition metal active sites, leading the field to conclude that transition metal complexes based on metals earlier in the periodic table, like chromium (Cr), were nonprivileged for the CO2RR. However, metals early in the table have sufficient reducing power to mediate the CO2RR and therefore could be selective in the correct coordination environment. This Account describes our efforts to develop and optimize novel Cr-based CO2RR catalyst systems through redox-active ligand modification strategies and the use of redox mediators (RMs). RMs are redox-active molecules which can participate cocatalytically during an electrochemical reaction, transferring electrons─often accompanied by protons─to a catalytic active site. Through mechanistic and computational work, we have found that ligand-based redox activity is key to controlling the intrinsic selectivity of these Cr compounds for CO2 activation. Ligand-based redox activity is also essential for developing cocatalytic systems, since it enables through-space interactions with reduced RMs containing redox-active planar aromatic groups, allowing charge transfer to occur within the catalyst assembly. Following a summary of our work, we offer a perspective on the possibilities for future development of catalytic and cocatalytic systems with early transition metals for small molecule activation.

Performance enhancement of rechargeable zinc-air battery through synergistic ex-solution of multi-component Pt/CoWO4-x catalysts

Advancing zinc-air battery (ZAB) technology necessitates the development of air cathode electrocatalyst systems that demonstrate high reactivity and stability. We introduce a novel method to fabricate a robust catalyst-support hybrid. This hybrid comprises Co-doped Pt nanoparticles (NPs) anchored on metal oxide (Ex-PtCoWO) nanofibers (NFs), synthesized via electrospinning followed by selective metal ex-solution. Controlling the ex-solution of metal NPs leads to a highly active and stable oxygen reduction reaction (ORR). Moreover, the three-dimensional CoWO4-x NFs network enhances the surface exposure of ex-solved metal NPs, thereby aiding both selective ex-solution and the provision of active sites for the oxygen evolution reaction (OER) during ZAB recharge. The Ex-PtCoWO NF exhibits an ORR half-wave potential of 0.89 V and an OER potential of 1.69 V at 10 mA cm−2 in alkaline media. ZABs utilizing Ex-PtCoWO NF show an extended cycle life of over 240 h with reduced charge-discharge polarization, compared to commercial catalysts.

Tandem catalysis in electrocatalytic nitrate reduction: Unlocking efficiency and mechanism

AbstractThe electrochemical nitrate reduction reaction (NO3RR) holds promise for ecofriendly nitrate removal. However, the challenge of achieving high selectivity and efficiency in electrocatalyst systems still significantly hampers the mechanism understanding and the large‐scale application. Tandem catalysts, comprising multiple catalytic components working synergistically, offer promising potential for improving the efficiency and selectivity of the NO3RR. This review highlights recent progress in designing tandem catalysts for electrochemical NO3RR, including the noble metal‐related system, transition metal electrocatalysts, and pulsed electrocatalysis strategies. Specifically, the optimization of active sites, interface engineering, synergistic effects between catalyst components, various in situ technologies, and theory simulations are discussed in detail. Challenges and opportunities in the development of tandem catalysts for scaling up electrochemical NO3RR are further discussed, such as stability, durability, and reaction mechanisms. By outlining possible solutions for future tandem catalyst design, this review aims to open avenues for efficient nitrate reduction and comprehensive insights into the mechanisms for energy sustainability and environmental safety.

(Invited) Forming Multifunctional Ceramics with Different ZrO2 Polymorphs: Mixed Ion-Electron Conducting Properties of Zirconium Titanium Oxides

Infiltrating porous electrodes with solution phase precursors is a strategy employed to improve performance, catalytic activity and longevity in high temperature electrochemical devices. For example, traditional Ni yttria-stabilized zirconia (Ni-YSZ) cermet anodes used in solid oxide fuel cells (SOFCs) are susceptible to carbon accumulation and to sulfur poisoning. To counter the effects of degradation, anodes have been infiltrated with secondary materials containing Sn, Ba, Al and a host of other constituents, typically at levels of 1-5% (by mass). Processing and preparing infiltrated electrodes, however, can lead to formation of new material phases that affect surface chemistry and electrode microstructure in unexpected ways.In this work, XRD and Raman spectroscopy are used to investigate the formation of functional zirconium titanate secondary phases in Ti/Zr oxides. Different zirconia polymorphs (either pure or stabilized with small amounts of yttria (YSZ)) mechanically mixed with TiO2 and heated above 1000 ˚C in stagnant air react to form several secondary phases. For sintering temperatures > 1100 ˚C, mixtures of TiO2 and m-ZrO2 form a ZrTiO4 secondary phase while mixtures of TiO2 and 3YSZ or 8YSZ form Zr5Ti7O24. The extent of secondary phase formation is enhanced with both higher sintering temperature and yttria content. The Zr5Ti7O24 secondary phase formed from TiO2/8YSZ samples sintered at 1400 ˚C exhibits unexpected mixed ionic and electronic conductivity at 800 ˚C. These findings suggest that secondary phases intentionally integrated into electrode architectures can improve the performance of high temperature electrocatalyst systems.

Interfacial P–O covalent bonds regulated electronic configuration in black phosphorus for improving oxygen evolution activity

Black phosphorus (P(black)) shows impressive physicochemical features for electrocatalysis including adjustable bandgap and high charge carrier mobility. However, the existence of solitary electron pairs in exfoliated P(black) nanosheets (EP(black)) leads to rapid surface degradation, resulting in unfavorable durability. Herein, a P–O bridge was created in the heterostructure EP(black)/vanadium-doped cobalt hydroxide with oxygen vacancy (EP(black)/V–CoO2-xH2) to stabilize and expedite oxygen evolution reaction (OER) activity. By bonding the solitary electron pairs of EP(black) and oxygen species (OH*) of V–CoO2-xH2, the distinctive P–O bridge resulted in important ligand effects that improved not merely the stability of EP(black) but effectively regulated the electron configuration of V–CoO2-xH2. DFT simulations revealed that directional interfacial electron migration from V–CoO2-xH2 to EP(black) facilitated the formation of pivotal OER intermediates and hence boosted OER activities. This study proposes a novel strategy to enhance the electrochemical properties of EP(black), which could be extended to a wide range of high-performance electrocatalyst systems.

Enhanced Alkaline Hydrogen Evolution Reaction through Lanthanide-Modified Rhodium Intermetallic Catalysts.

Design of highly efficient electrocatalysts for alkaline hydrogen evolution reaction (HER) is of paramount importance for water electrolysis, but still a considerable challenge because of the slow HER kinetics in alkaline environments. Alloying is recognized as an effective strategy to enhance the catalytic properties. Lanthanides (Ln) are recognized as an electronic and structural regulator, attributed to their unique 4f electron behavior and the phenomenon known as lanthanide contraction. Here, a new class of Rh3Ln intermetallics (IMs) are synthesized using the sodium vapor reduction method. The alloying process induced an upshift of the d-band center and electron transfer from Ln to Rh, resulting in optimized adsorption and dissociation energies for H2O molecules. Consequently, Rh3Tb IMs exhibited outstanding HER activity in both alkaline environments and seawater, displaying an overpotential of only 19mV at 10mAcm-2 and a Tafel slope of 22.2mV dec-1. Remarkably, the current density of Rh3Tb IMs at 100mV overpotential is 8.6 and 5.7 times higher than that of Rh/C and commercial Pt/C, respectively. This work introduces a novel approach to the rational design of HER electrocatalysis and sheds light on the role of lanthanides in electrocatalyst systems.

Efficient and selective glycerol electrolysis for the co-production of lactic acid and hydrogen with multi-component Pt/C-zeolite catalyst

Among various electrochemical reactions to produce fuels and chemicals, glycerol electrolysis to co-produce hydrogen and lactic acid has received great attention. However, studies have shown the benchmark Pt based catalysts are insufficient in selectively catalysing the glycerol to lactic acid transformation, resulting in a low yield of lactic acid. Here we report a study on glycerol electrolysis with anion-exchange membrane electrode assembly electrolyser. The reaction conditions including mass transport, temperature, current density and KOH concentration were optimised, among which temperature played a significant role in facilitating the reaction rate and thermodynamics. With the optimised condition a multicomponent Pt/C-zeolite electrocatalyst system (Pt/C-CBV600) was developed and tested, which is capable to increase the lactic acid selectivity to 57.3% from the 33.8% with standalone Pt/C. Although the detailed mechanism required further investigation, it is hypothesised that the CBV600 zeolite with abundant Lewis acid surface sites can effectively bind the dihydroxyacetone intermediate, and drive the reaction towards pyruvaldehyde heterogeneously, the key step to form lactic acid.

Engineering pore-size distribution of metal-loaded carbon catalysts by in situ cavitation for boosting electrochemical mass transfer

In addition to highly active catalytic sites, mass transfer, especially diffusion of the reactant/product also play important roles in supported electrocatalyst systems. However, compared with the morphologies and specific surface areas, the pore structures of the catalyst supports and their influence on catalytic mass transfer have received less attention. Herein, we propose a universal in situ cavitation strategy to regulate the pore size distributions on the metal-loaded carbon through nitro modification on the molecule-based precursors, without significantly changing the electronic structures of the active metal centers. Gas sorption experiments, electrocatalytic measurements and molecular dynamic simulations certified that the increasing mesopore/macropore ratios can remarkably facilitate the diffusion coefficient, enabling improved oxygen evolution kinetics with 71 mV overpotential dropping at 10 mA·cm−2 compared with the nitro-free counterpart. This work demonstrates that the pore size distributions of the catalyst support should be another nonnegligible parameter on boosting the overall electrocatalytic performance.

2 A cm-2 Level Large-Scale Production of Hydrogen Enabled by Constructing Higher Capacity of Interface "Electron Pocket".

The batch production of high-purity hydrogen is a key problem that restricts the progress of fuel cells and the blueprint for achieving carbon neutrality. Transition-metal chalcogenide heterojunctions exhibit certain activity toward electrochemical overall water splitting (EOWS), but their high-current-density catalytic performances are still unsatisfactory due to the slow kinetic progression (H* or *O → *OOH). Inspired by the "electron pocket" theory, we designed a Ni-Mo bimetallic disulfide interface heterojunction electrocatalyst system (NM-IHJ-V) with high electronic storage capacity around the Fermi level (-0.5 eV, +0.5 eV) (e-DFE), which injects more power into the kinetic progression processes of intermediate species in the EOWS process. Consequently, it achieves a superhigh current density of 2 A cm-2 level for EOWS (only 1.98 V voltage is needed), which is 11.23-fold higher than that of the benchmarked Pt/C//IrO2 (178 mA cm-2@1.98 V), as well as an excellent long-term stability of 200 h. Most strikingly, NM-IHJ-V can efficiently produce hydrogen at currents up to 5 A. Our proposed strategy of constructing catalysts to produce hydrogen at superhigh current density through the electron pocket theory will supply valuable insights for the designing other catalytic systems.

Operando identification of synergistic dynamic for cobalt-tungsten-based bimetallic electrocatalysts in oxygen evolution reaction

The bimetallic electrocatalysts in oxygen evolution reaction (OER) have been the subject of numerous investigations. However, due to their heterogeneous nature, understanding the individual roles and reaction mechanisms of the catalytic sites remains challenging. Herein, we present an electrocatalyst system featuring a cobalt-tungsten (Co/W)-based bimetallic pair. In this bimetallic series, the catalytic activity displays a trend, with the overpotential of 385 mV at 10 mAcm−2 and the lowest Tafel slope of 70 mVdec−1 under alkaline conditions for the OER. Operando characterization reveals the Co site functions as the active site, undergoing a CoIII/CoIV redox cycle, while the W site also exhibits a simultaneous redox cycle, acting as a driving force to trigger the OER process. We propose a catalytic cycle that demonstrates the synergistic effect of hetero-atoms, in which they follow a similar O–O bond-forming step to metal oxides under OER conditions yet exhibit distinct rate-determining steps. Our research contributes to the understanding of bimetallic electrocatalysts as promising systems for fundamental studies and improved OER performance.

Effect of molybdenum phosphorus-based single/double-atom catalysts on hydrogen evolution reaction: First principles

In terms of green energy, it is critical to investigate the carrier stability and hydrogen evolution reaction activity of atomic catalysts. On the (111) and (101) surfaces of MoP, we investigate how single and double atom interactions affect HER activity. According to the results, the Ru/Ni@MoP(111) catalyst's energy barrier and hydrogen evolution free energy are 0.012 eV and 0.129 eV, respectively, during hydrolysis. In contrast, Pt/Ni@MoP(101) requires only 0.087 eV energy to absorb in order to produce OH∗ and H∗, demonstrating how effectively the diatom can increase the activity of the catalyst surface. Additionally, the localized surface plasmon resonance effect, which benefits double-atom catalysts, can be induced by precious metals. Ni has good HER activity in general, which can significantly lower the price of precious metals. Homoplastically, it is demonstrated that the MoP stable surface has outstanding hydrogen evolution activity and functions well as a carrier. A research foundation for expanding the synergistic law of the novel electrocatalyst system and multi-atomic loads is provided by the study's revelation of the structure-activity link of catalysts.

Effects of Mesoporosity and Conductivity of Hierarchically Porous Carbon Supports on the Deposition of Pt Nanoparticles and Their Performance as Electrocatalysts for Oxygen Reduction Reaction in Alkaline Media.

The structural characteristics of supports, such as surface area and type of porosity, affect the deposition of electrocatalysts and greatly influence their electrochemical performance in fuel cells. In this work, we use a series of high surface area hierarchical porous carbons (HPCs) with defined mesoporosity as model supports to study the deposition mechanism of Pt nanoparticles. The resulting electrocatalysts are characterized by several analytical techniques, and their electrochemical performance is compared to a state-of-the-art, commercial Pt/C system. Despite the similar chemical composition and surface area of the supports, as well as similar amounts of Pt precursor used, the size of the deposited Pt nanoparticles varies, and it is inversely proportional to the mesopore size of the system. In addition, we show that an increase in the size of the catalyst particles can increase the specific activity of the oxygen reduction reaction. We also report on our efforts to improve the overall performance of the above electrocatalyst systems and show that increasing the electronic conductivity of the carbon support by the addition of highly conductive graphene sheets improves the overall performance of an alkaline fuel cell.

Development, Essence, and Application of a Metal-Catalysis Battery.

ConspectusIn the pursuit of maximizing the energy supply and sustainable energy development, high-energy-density energy storage systems beyond lithium-ion batteries are surging. The metal-catalysis battery, composed of a metal anode, electrolyte, and redox-coupled electrocatalyst cathode with gas, liquid, or solid as active reactants, is regarded as a promising energy storage and conversion system due to its dual functions of energy storage and chemical production. In this system, with the assistance of a redox-coupled catalyst, during discharging, the reduction potential energy of the metal anode is converted into chemicals along with electrical energy generation, while the external electrical energy is translated to the reduction potential energy of the metal anode and the oxidation potential energy of the reactants during charging. In this loop, the electrical energy and sometimes chemicals can be generated simultaneously. Although intensive effort has been devoted to the exploration of redox-coupled catalysts, the essence of the metal-catalysis battery, which is the prerequisite for further development and application, has been overlooked.In this Account, we present the journey of the metal-catalysis battery from development to essence and application and propose that the metal-catalysis battery system, which combines energy storage and electrocatalytic redox reactions with the characteristics of temporal decoupling and spatial coupling and an energy-conversion paradigm from electrical energy to chemicals via electrochemical energy storage, is achieved. First, inspired by the Zn-air/Li-air battery, we developed and realized Li-CO2/Zn-CO2 batteries and enriched the functions of the metal-catalysis battery from energy storage to chemical production. Based on OER/ORR and OER/CDRR catalysts, we have further explored OER/NO3-RR and HzOR/HER coupled catalysts and developed Zn-nitrate and Zn-hydrazine batteries. By extending the redox-coupled electrocatalyst systems from O, C species to N species and others, the metal-catalysis battery systems would develop from metal-Ox, Cx to metal-Nx and other batteries. Then, from Zn-CO2 and Zn-hydrazine batteries, we found that the overall reaction is decoupled into two separate reduction and oxidation reactions via the cathodic discharge and charge processes, and we further extracted the essence of the metal-catalysis battery, namely, the temporal-decouple and spatial-couple (TD-SC) mechanism, which is completely opposite to the conventional temporal couple and spatial decouple in electrochemical water splitting. Based on the TD-SC mechanism, we developed various applications of metal-catalysis batteries for the green and efficient synthesis of fine chemicals by modifying the metal anode and redox-coupled catalysts and electrolytes, including the Li-N2/H2 battery for NH3 synthesis and the organic Li-N2 battery for fine chemical synthesis. Finally, the main challenges and the possible opportunities for the metal-catalysis battery are discussed, including the rational design of highly efficient redox-coupled electrocatalysts and green electrochemical synthesis. The deep insight into the metal-catalysis battery will provide an alternative approach to energy storage and chemical production.

Designing mixed-metal electrocatalyst systems for photoelectrochemical dinitrogen activation.

Efficient artificial photosynthesis systems are currently realized as catalyst- and surface-functionalized photovoltaic tandem-and triple-junction devices, enabling photoelectrochemical (PEC) water oxidation while simultaneously recycling CO2 and generating hydrogen as a solar fuel for storable renewable energy. Although PEC systems also bear advantages for the activation of dinitrogen - such as a high system tunability with respect to the electrocatalyst integration and a directly controllable electron flux to the anchoring catalyst through the adjustability of incoming irradiation - only a few PEC devices have been developed and investigated for this purpose. We have developed a series of photoelectrodeposition procedures to deposit mixed-metal electrocatalyst nanostructures directly on the semiconductor surface for light-assisted dinitrogen activation. These electrocatalyst compositions containing Co, Mo and Ru in different atomic ratios follow previously made recommendations of metal compositions for dinitrogen reduction and exhibit different physical properties. XPS studies of the photoelectrode surfaces reveal that our electrocatalyst films are to a large degree nitrogen-free after their fabrication, which is generally difficult to achieve with traditional magnetron sputtering or e-beam evaporation techniques. Initial chronoamperometric measurements of the p-InP photoelectrode coated with the Co-Mo alloy electrocatalyst show higher photocurrent densities in the presence of N2(g) than in the presence of Ar at -0.09 V vs. RHE. Indications of successful dinitrogen activation have also been found in consecutive XPS studies, where both N 1s and Mo 3d spectra reveal evidence of nitrogen-metal interactions.

Interfacial Engineering of Polycrystalline Pt5 P2 Nanocrystals and Amorphous Nickel Phosphate Nanorods for Electrocatalytic Alkaline Hydrogen Evolution.

Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is important for hydrogen economy but suffers from sluggish reaction kinetics due to a large water dissociation energy barrier. Herein, Pt5 P2 nanocrystals anchoring on amorphous nickel phosphate nanorods as a high-performance interfacial electrocatalyst system (Pt5 P2 NCs/a-NiPi) for the alkaline HER are demonstrated. At the unique polycrystalline/amorphous interface with abundant defects, strong electronic interaction, and optimized intermediate adsorption strength, water dissociation is accelerated over abundant oxophilic Ni sites of amorphous NiPi, while hydride coupling is promoted on the adjacent electron-rich Pt sites of Pt5 P2 . Meanwhile, the ultra-small-sized Pt5 P2 nanocrystals and amorphous NiPi nanorods maximize the density of interfacial active sites for the Volmer-Tafel reaction. Pt5 P2 NCs/a-NiPi exhibits small overpotentials of merely 9 and 41mV at -10 and -100mA cm-2 in 1M KOH, respectively. Notably, Pt5 P2 NCs/a-NiPi exhibits an unprecedentedly high mass activity (MA) of 14.9mA µgPt -1 at an overpotential of 70mV, which is 80 times higher than that of Pt/C and represents the highest MA of reported Pt-based electrocatalysts for the alkaline HER. This work demonstrates a phosphorization and interfacing strategy for promoting Pt utilization and in-depth mechanistic insights for the alkaline HER.

Electrosynthesis of Low Pt‐Loaded High Entropy Catalysts for Effective Hydrogen Evolution with Improved Acidic Durability

The synergistic effect in multi‐metal electrocatalysts has gained attention as an efficient strategy for enhancing intrinsic electrocatalytic activities. In this study, a facile electrodeposition technique is used to synthesize a multi‐metal high entropy catalyst (HEC) for efficient electrocatalytic hydrogen production. To boost the synergistic effect between noble metals and transition metals, the Pt ratio is controlled in a multi‐metal electrocatalyst system. The prepared Pt‐involved HEC (Pt‐HEC) exhibits a bamboo‐like morphology with uniformly distributed elements. The 2.5 mM Pt‐HEC has outstanding electrocatalytic activity toward hydrogen evolution reaction (HER) among other Pt‐HECs, with a low overpotential of 70 mV and a Tafel slope value of 47 mV dec−1. Additionally, the Pt mass activity of the 2.5 mM Pt‐HEC is 5.6 times higher than commercial Pt/C electrocatalyst owing to the improved synergistic effect with an optimized Pt ratio. According to the electrochemical impedance spectroscopy (EIS) analysis, the proton‐coupled electron transfer (PCET) process occurs more quickly in the 2.5 mM Pt‐HEC electrocatalyst, confirming its smaller charge transfer resistance properties compared to those of the 5 and 1 mM Pt‐HEC. Therefore, HEC systems can be extensively encouraged as a platform for improving synergistic effects and enhancing electrocatalytic activities for a highly efficient HER electrocatalyst.

The Electrochemical Growth of 2D Metals on Insulators Using a Graphene Interface

2D confined metals (2D-M) under heteroepitaxial relations with graphene (Gr) allow for the potential control of chemical properties of the 2D-M by an external electric field. If this external electric field is supplied by an insulating substrate (such as a dielectric or a ferroelectric), then it can enable a non-Faradaic manipulation of electrocatalytic reactions via the M-Gr electrocatalyst system. In this work, we will explore the architecture of a 2D metal-graphene (2D M-Gr), where the substrate is supplying an electric field as well as fulfilling the role of the insulating substrate (dielectric) in the system. The insulating substrate will carry an embedded electron charge at the interface between two dielectric (DE) layers, close to the surface of the metal, allowing for electronic influence on the metal. In this system, graphene acts as an imperfect screener of electric fields allowing the dielectric/ferroelectric-generated field to influence the metal. We find that providing an approximate potential of 0.1 V yields a significant increase in the hydrogen evolution current within a 2D platinum/graphene (2D Pt/Gr) system. Extended X-ray absorption fine structure (EXAFS) studies are used to examine 2D M-Gr epitaxy. EXAFS results indicate a strain condition imposed by Gr on the metal grown, where Gr is constraining nearest-neighbor distances through epitaxial directions. Experimental research on the strain induced in graphene-templated Pt monolayers by Alamgir et al. found that a single graphene layer induces a 3.5% compressive strain on the Pt adlayer deposited onto it, increasing the catalytic activity of the system In the 2D M-Gr system, our strained, epitaxially grown metal on Gr will be demonstrated on an Au/Gr/DE and Pd/Gr/DE system.