Intrinsic Electrocatalytic Activity Research Articles

Boron-incorporated IrO2-Ta2O5 coating as an efficient electrocatalyst for acidic oxygen evolution reaction

The Ir-based electrocatalysts for the acidic oxygen evolution reaction (OER) have demonstrated remarkable durability. Enhancing the Ir-based electrocatalytic activity still remains crucial owing to the scarcity of iridium. Here, a high-temperature sintering technique is employed to fabricate a boron (B)-incorporated IrO2-Ta2O5 coating with an almost perfect rutile-type crystal structure on a corrosion-resistant titanium substrate, ensuring exceptional stability for the acidic OER. The B-incorporated IrO2-Ta2O5 electrode fabricated in a mixed solution of 0.6 M H3BO3, exhibits an overpotential of 210 mV at a current density of 10 mA cm−2 and a lower Tafel slope of 34.2 mV dec−1 in a 0.5 M H2SO4 solution, which is far lower than the 272 mV overpotential and the 45.3 mV dec−1 of the IrO2-Ta2O5/Ti electrode. The electrode possesses a minimal potential increase even after undergoing continuous OER for 400 h at a high current density of 100 mA cm−2 in a 0.5 M H2SO4 solution. The incorporation of B species into IrO2-Ta2O5 effectively fine-tunes the electronic structure of Ir active sites, leading to a substantial enhancement of the intrinsic electrocatalytic activity. This study provides promising prospects for reducing the energy consumption of noble IrO2-based electrocatalysts in the practical application of electrochemical industry for the acidic OER.

Stabilization of active ultrathin amorphous ruthenium oxide via constructing electronically interacted heterostructure for acidic water oxidation

Amorphous RuOx (a-RuOx) with disordered atomic arrangement and abundant coordinatively unsaturated Ru sites possesses high intrinsic electrocatalytic activity for oxygen evolution reaction (OER). However, the a-RuOx is prone to fast corrosion during OER in strong acid. Here, we realized the stabilization of an ultrathin a-RuOx layer via constructing heterointerface with crystalline α-MnO2 nanorods array (MnO2@a-RuOx). Benefiting from the strong electronic interfacial interaction, the as-formed MnO2@a-RuOx electrocatalyst display an ultralow overpotential of 128 mV to reach 10 mA cm−2 and stable operation for over 100 h in 0.1 M HClO4. The assembled proton exchange membrane (PEM) water electrolyzer reach 1 A cm−2 at applied cell voltage of 1.71 V. Extensive characterizations indicate the MnO2 substrate work as an electron donor pool to prevent the overoxidation of Ru sites and the OER proceeds in adsorbent evolution mechanism process without involving lattice oxygen. Our work provides a promising route to construct robust amorphous phase electrocatalysts.

Iron Active Center Coordination Reconstruction in Iron Carbide Modified on Porous Carbon for Superior Overall Water Splitting.

In this work, a novel liquid nitrogen quenching strategy is engineered to fulfill iron active center coordination reconstruction within iron carbide (Fe3C) modified on biomass-derived nitrogen-doped porous carbon (NC) for initiating rapid hydrogen and oxygen evolution, where the chrysanthemum tea (elm seeds, corn leaves, and shaddock peel, etc.) is treated as biomass carbon source within Fe3C and NC. Moreover, the original thermodynamic stability is changed through the corresponding force generated by liquid nitrogen quenching and the phase transformation is induced with rich carbon vacancies with the increasing instantaneous temperature drop amplitude. Noteworthy, the optimizing intermediate absorption/desorption is achieved by new phases, Fe coordination, and carbon vacancies. The Fe3C/NC-550 (550 refers to quenching temperature) demonstrates outstanding overpotential for hydrogen evolution reaction (26.3mV at -10 mAcm-2) and oxygen evolution reaction (281.4 mV at 10mAcm-2), favorable overall water splitting activity (1.57 V at 10 mAcm-2). Density functional theory (DFT) calculations further confirm that liquid nitrogen quenching treatment can enhance the intrinsic electrocatalytic activity efficiently by optimizing the adsorption free energy of reaction intermediates. Overall, the above results authenticate that liquid nitrogen quenching strategy open up new possibilities for obtaining highly active electrocatalysts for the new generation of green energy conversion systems.

Effect of Intrinsic Ferroelectric Phase Transition on Hydrogen Evolution Electrocatalysis

AbstractHeterogeneous electrocatalysis closely relies on the electronic structure of the catalytic materials. The ferroelectric‐to‐paraelectric phase transition of the materials also involves a change in the state of electrons that could impact the electrocatalytic activity, but such correlation remains unexplored. Here, we demonstrate experimentally and theoretically that the intrinsic electrocatalytic activity could be regulated as exampled by hydrogen evolution reaction catalysis over two‐dimensional ferroelectric CuInP2S6. The obvious discontinuity in the overpotential and apparent activation energy values for CuInP2S6 electrode are illustrated during the ferroelectric‐to‐paraelectric phase transition caused by copper displacement around Tc point (318 K), revealing the ferroelectro‐catalytic effect on thermodynamics and kinetics of electrocatalysis. When loading Pt single atom on the CuInP2S6, the paraelectric phase one showed an improved hydrogen evolution activity with smaller apparent activation energy over the ferroelectric phase counterpart. This is attributed to the copper hopping between two sulfur planes, which alternate between strong and weak H adsorption at the Pt sites to simultaneously promote H+ reactant adsorption and H2 product desorption.

Enhancing Intrinsic Electrocatalytic Activity of Pt/C Nanoparticles for Ox-ygen Reduction Reaction in Acidic Media by Microwave-Assisted Synthesis

Abstract: This study is focused on the enhancement of the intrinsic electrocatalytic activity of Pt nanoparticles supported on C (Pt/C NPs) towards Oxygen Reduction Reaction (ORR) in acidic media. The goal was to investigate the effect of microwave-assisted synthesis on the electrocatalytic perfor-mance of Pt/C NPs towards ORR. Thus, Pt/C NPs were synthesized using a microwave-assisted method and by a conventional heating method; structural and morphological characteristics were an-alyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Electrochemical studies were performed using the rotating disk electrode technique to evaluate the ORR performance. Microwave-assisted synthesis produced Pt/C NPs with a smaller particle size (6.3 ± 0.2 nm) than con-ventionally synthesized nanoparticles (8.6 ± 0.3 nm). Electrochemical analysis showed that the micro-wave-synthesized Pt/C NPs exhibited higher mass activity (4.6 ± 0.8 mA･g-1Pt) for ORR compared to conventionally synthesized nanoparticles (1.9 ± 0.4 mA･mA･g-1Pt). These results demonstrate that microwave-assisted synthesis enhances the intrinsic electrocatalytic activity of Pt/C NPs for ORR in acidic media. These findings have important implications for the development of efficient electrocat-alysts for fuel cell applications. Background: The synthesis and characterization of platinum nanoparticles on C are crucial for ad-vancing electrocatalysis, particularly in the context of potential applications in fuel cells. This study builds on previous research, focusing on two distinct synthesis methods to enhance our understanding of their impact on nanoparticle properties and electrocatalytic performance. Objective: To investigate the synthesis efficiency, structural characteristics, and electrocatalytic activ-ities of platinum nanoparticles on C using microwave-assisted heating and conventional synthesis re-actor heating. The objective is to discern any significant differences in particle size, structure, and electrocatalytic performance between the two synthesis methods. method: The synthesis involved a comparative analysis of platinum nanoparticles using microwave-assisted and conventional heating methods. Chemical composition analysis verified the synthesis efficiency, and structural and morphological characterizations were performed using X-ray Diffraction and Transmission Electron Microscopy. Electrochemical studies employed the rotating disk electrode technique, with activation and evaluation conducted through cyclic voltammetry, and the oxygen reduction reaction studied via linear sweep voltammetry in an acidic media (0.5 mol⋅L-1 H2SO4). Methods: The synthesis involved a comparative analysis of platinum nanoparticles using microwave-assisted and conventional heating methods. Chemical composition analysis verified the synthesis ef-ficiency, and structural and morphological characterizations were performed using X-ray Diffraction and Transmission Electron Microscopy. Electrochemical studies employed the rotating disk electrode technique, with activation and evaluation conducted through cyclic voltammetry, and the oxygen re-duction reaction studied via linear sweep voltammetry in an acidic media (0.5 mol⋅L-1 H2SO4). Results: Well-supported platinum nanoparticles with a face-centered cubic structure were obtained on C using both synthesis methods. However, microwave-synthesized particles (6.3 ± 0.2 nm) exhibited a smaller size compared to conventionally synthesized particles (8.6 ± 0.3 nm). Electrochemical as-sessment revealed superior mass activity for microwave-synthesized material (4.6 ± 0.8 mA･g-1Pt), outperforming commercial Pt nanoparticles (3.0 ± 0.3 mA･g-1Pt) and conventionally synthesized ma-terial (1.9 ± 0.4 mA･mA･g-1Pt). Conclusion: This study concludes that microwave-assisted synthesis yields platinum nanoparticles on C with enhanced electrocatalytic performance, as evidenced by the smaller particle size and superior mass activity compared to conventionally synthesized material and commercial Pt nanoparticles. These findings highlight the potential of microwave-synthesized Pt nanoparticles for applications in fuel cells.

Effect of Intrinsic Ferroelectric Phase Transition on Hydrogen Evolution Electrocatalysis.

Heterogeneous electrocatalysis closely relies on the electronic structure of the catalytic materials. The ferroelectric-to-paraelectric phase transition of the materials also involves a change in the state of electrons that could impact the electrocatalytic activity, but such correlation remains unexplored. Here, we demonstrate experimentally and theoretically that the intrinsic electrocatalytic activity could be regulated as exampled by hydrogen evolution reaction catalysis over two-dimensional ferroelectric CuInP2S6. The obvious discontinuity in the overpotential and apparent activation energy values for CuInP2S6 electrode are illustrated during the ferroelectric-to-paraelectric phase transition caused by copper displacement around Tc point (318 K), revealing the ferroelectro-catalytic effect on thermodynamics and kinetics of electrocatalysis. When loading Pt single atom on the CuInP2S6, the paraelectric phase one showed an improved hydrogen evolution activity with smaller apparent activation energy over the ferroelectric phase counterpart. This is attributed to the copper hopping between two sulfur planes, which alternate between strong and weak H adsorption at the Pt sites to simultaneously promote H+ reactant adsorption and H2 product desorption.

Glassy State Hydroxide Materials for Oxygen Evolution Electrocatalysis.

Hydroxides are the archetype of layered crystals with metal-oxygen (M-O) octahedron units, which have been widely investigated as oxygen evolution reaction (OER) catalysts. However, the better crystallinity of hydroxide materials, the more perfect octahedral symmetry and atomic ordering, resulting in the less exposed metal sites and limited electrocatalytic activity. Herein, a glassy state hydroxide material featuring with short-range order and long-range disorder structure is developed to achieve high intrinsic activity for OER. Specifically, a rapid freezing point precipitation method is utilized to fabricate amorphous multi-component hydroxide. Owing to the freezing-point crystallization environment and chaotic M-O (M = Ni/Fe/Co/Mn/Cr etc.) structures, the as-fabricated NiFeCoMnCr hydroxide exhibit a highly-disordered glassy structure, as-confirmed by X-ray/electron diffraction, enthalpic response, and pair distribution function analysis. The as-achieved glassy-state hydroxide materials display a low OER overpotential of 269mV at 20mA cm-2 with a small Tafel slope of 33.3mV dec-1 , outperform the benchmark noble-metal RuO2 catalyst (341mV, 84.9mV dec-1 ) . Operando Raman and density functional theory studies reveal that the glassy state hydroxide converted into disordered active oxyhydroxide phase with optimized oxygen intermediates adsorption under low OER overpotentials, thus boosting the intrinsic electrocatalytic activity.

Iron-doped nickel-molybdate nanoarrays for efficient urea oxidation reaction

Designing efficient electrocatalysts based on non-noble metals for urea oxidation reaction (UOR) is highly desirable. Herein, a facile approach is reported for the construct of Fe-NiMoO4-NF as an efficient electrocatalyst toward UOR. Remarkably, Fe-NiMoO4-NF displayed excellent UOR activity with tiny potentials of 1.362 V delivering large current density of 100 mA cm−2, surpassing other NiMoO4-NF, Fe-NiO-NF, and NF catalysts. Experimental results suggested that Fe-doping can moderate the electron structure of NiMoO4-NF, simultaneously enhancing intrinsic electrocatalytic activity and speeding up the UOR kinetics. This work highlights the potential benefits of electron structure manipulation for the rational design of advanced electrocatalysts for large-scale urea oxidation reaction.

Modified electronic structure and enhanced hydroxyl adsorption make quaternary Pt-based nanosheets efficient anode electrocatalysts for formic acid-/alcohol-air fuel cells

Surface/interface engineering of a multimetallic nanostructure with diverse electrocatalytic properties for direct liquid fuel cells is desirable yet challenging. Herein, using visible light, a class of quaternary PtAgBiTe ultrathin nanosheets is fabricated and used as high-performance anode electrocatalysts for formic acid-/alcohol-air fuel cells. The modified electronic structure of Pt, enhanced hydroxyl adsorption, and abundant exterior defects afford Pt1Ag0.1Bi0.16Te0.29/C high intrinsic anodic electrocatalytic activity to boost the power densities of direct formic acid-/methanol-/ethanol-/ethylene glycol-/glycerol-air fuel cells, and the corresponding peak power density of Pt1Ag0.1Bi0.16Te0.29/C is respectively 129.7, 142.3, 105.4, 124.3, and 128.0 mW cm−2, considerably outperforming Pt/C. Operando in situ Fourier transform infrared reflection spectroscopy reveals that formic acid oxidation on Pt1Ag0.1Bi0.16Te0.29/C occurs via a CO-free direct pathway. Density functional theory calculations show that the presence of Ag, Bi, and Te in Pt1Ag0.1Bi0.16Te0.29 suppresses CO* formation while optimizing dehydrogenation steps and synergistic effect and modified Pt effectively enhance H2O dissociation to improve electrocatalytic performance. This synthesis strategy can be extended to 43 other types of ultrathin multimetallic nanosheets (from ternary to octonary nanosheets), and efficiently capture precious metals (i.e., Pd, Pt, Rh, Ru, Au, and Ag) from different water sources.

Surface oxygen vacancy engineering of Cr-doped FeNi3/NiFe2O4 Mott-Schottky heterojunction as efficient electrocatalyst for high current density water oxidation

The defect engineering at the surface by filling of oxygen vacancies during OER causing surface reconstruction is considered to be a unique way to boost up intrinsic electrocatalytic activity, especially towards oxygen evolution reaction (OER) mechanism. The present study aimed creation of large number of oxygen vacancies by Cr-doping into FeNi3/NiFe2O4 Mott-Schottky heterojunction electrocatalyst causing much desirable surface engineering and electronic modulation in favour of OER activity. The optimized heterojunction nanoparticles exhibited an excellent catalytic activity with low overpotential of 246 mV at the current density of 20 mA cm−2 with low Tafel slope value of 55 mV dec−1 for OER. Such oxygen vacancy-aided surface reconstruction during OER demonstrated an outstanding durability over 200 h even at high current density of 1000 mA cm−2 in 1 M KOH electrolyte. The surface oxygen vacancy engineering with the help of ex-situ Raman spectroscopy at different anodic potentials reveals the filling of vacancies and generation of MOOH as surface reconstruction of electrocatalyst during OER, also supported by XPS, TEM and EELS analyses.

Single‐nanoparticle electrochemical collision for study of the size‐dependent activity of Au nanoparticles during hydrogen evolution reaction

AbstractIdentifying the intrinsic electrocatalytic activity of an individual nanoparticle is essential to reveal the structure‐activity relations of catalysts. However, it is challenging as the performance of catalysts is typically evaluated with ensembles, providing an elusive averaged response of complex catalyst‐modified electrodes. Herein, a single‐nanoparticle electrochemical collision (SNEC)‐based method was employed to characterize the electrocatalysis of citrate‐capped Au NPs with six different particle sizes, and investigate the size‐dependent electrocatalytic activity of Au NPs toward hydrogen evolution reaction (HER) at the single‐particle level. Results showed that the geometric activity of Au NPs showed a decreasing trend as the size increased from 5 nm to 40 nm, consisting with the linear sweep voltammetry (LSV) data that the onset potentials and potentials to reaching at HER currents of 50 μA cm−2 shifted negatively as the size of Au NPs increased. Also noteworthy is that the measured geometric activity of single Au NP toward HER was 5~6 orders of magnitude higher than the ensemble data derived from the LSV tests. The extraordinary enhancement of catalytic activity is believed to originate from the high accessible surface area of monodispersed Au NPs. Hence, the proposed SNEC‐based method could investigate the intrinsic electrocatalytic activity of NPs in solution at the single‐particle level, and achieve true size‐activity correlation, which may provide effective guidance for the rational design of advanced electrocatalysts.

An on-site and portable electrochemical sensing platform based on spinel zinc ferrite nanoparticles for the quality control of paracetamol in pharmaceutical samples.

In this study, crystalline spinel zinc ferrite nanoparticles (ZnFe2O4 NPs) were successfully prepared and proposed as a high-performance electrode material for the construction of an electrochemical sensing platform for the detection of paracetamol (PCM). By modifying a screen-printed carbon electrode (SPE) with ZnFe2O4 NPs, the electrochemical characteristics of the ZnFe2O4/SPE and the electrochemical oxidation of PCM were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV) methods. The calculated electrochemical kinetic parameters from these techniques including electrochemically active surface area (ECSA), peak-to-peak separation (ΔEp), charge transfer resistance (Rct), standard heterogeneous electron-transfer rate constants (k0), electron transfer coefficient (α), catalytic rate constant (kcat), adsorption capacity (Γ), and diffusion coefficient (D) proved that the as-synthesized ZnFe2O4 NPs have rapid electron/mass transfer characteristics, intrinsic electrocatalytic activity, and facilitate the adsorption-diffusion of PCM molecules towards the modified electrode surface. As expected, the ZnFe2O4/SPE offered excellent analytical performance towards sensing of PCM with a detection limit of 0.29 μM, a wide linear range of 0.5-400 μM, and high electrochemical sensitivity of 1.1 μA μM-1 cm-2. Moreover, the proposed ZnFe2O4-based electrochemical nanosensor also exhibited good repeatability, high anti-interference ability, and practical feasibility toward PCM sensing in a pharmaceutical tablet. Based on these observations, the designed electrochemical platform not only provides a high-performance nanosensor for the rapid and highly efficient detection of PCM but also opens a new avenue for routine quality control analysis of pharmaceutical formulations.

Modulating the electronic structure of VS2via Ru decoration for an efficient pH-universal electrocatalytic hydrogen evolution reaction.

High-efficiency water electrolysis over a broad pH range is desirable but challenging. Herein, Ru-decorated VS2 on carbon cloth (Ru-VS2/CC) has been in situ synthesized, which features the regulated electronic structure of VS2 by introducing Ru. It is remarkable that the optimal Ru-VS2/CC displays excellent electrocatalytic hydrogen evolution activity with overpotentials of 89 and 87 mV at -10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively. Theoretical calculations and electrocatalytic measurements have demonstrated that introducing Ru induces an enhanced charge density around the Fermi level, facilitating charge transfer and speeding up the electrocatalytic HER kinetics. The Gibbs free energy of the hydrogen intermediate (ΔGH*) of Ru-VS2/CC (0.23 eV) is much closer to zero than that of pure VS2 (0.51 eV) and Ru (-0.37 eV), demonstrating an easier hydrogen adsorption and desorption process for Ru-VS2/CC. The more favorable ΔGH*, differential charge density and the d-band center endow Ru-VS2 with enhanced intrinsic electrocatalytic activity. This study presents a feasible strategy for enhancing electrocatalytic HER activity by the regulation of the electronic structure and the rational integration of dual active components.

Non-PGM Cathode Electrocatalysts for PEM Fuel Cells

Polymer electrolyte membrane fuel cells, PEMFCs, are considered the most ideal next generation energy conversion device, able to provide power to a broad range of applications; automotive, combined heat and power, portable electronic devices. Pt-based electrocatalysts are regarded as ideal for promoting the desired redox reactions of a fuel cell, especially the sluggish oxygen reduction at the cathode, ORR. High expense and scarcity of Pt are the greatest impediments to successful commercialization of this technology. The replacement of unsustainable noble-metal catalysts with platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) is essential for material wise and market value viable PEMFCs.Among the different attempts towards non-PGM catalysts, incorporating atomically dispersed transition metal atoms (Fe, Mn, etc.) and heteroatoms (N, S, etc.) into carbon frameworks is the most promising [1,2]. Large specific surface area, high intrinsic ORR electrocatalytic activity, efficient porosity and sufficient stability in acid media and/or in the actual working environment are the least requirements to consider when designing the catalysts. So far, despite the tremendous efforts, many drawbacks still persist that include poor understanding of the nature of active centres and their control over the synthesis, as well as fast decay of the structure under operation.In this work, we will present a rationally designed strategy to prepare hybrid composite catalysts by developing Fe–N–C materials onto different 2D and 3D templates [3,4] with differentiated surface chemistry (silicon and heteroatom-doped carbon structures). Despite structural and physicochemical characterization, the study includes extensive electrochemical characterization in terms of activity and durability in relative to the application conditions. An example is depicted in Figure 1 for a single atom Fe-N-C catalyst synthesized using porous silica nanotubes as the sacrificial template resulting in a hierarchically porous structure with a surface area of 370 m2/g. Electrochemical study revealed a half-wave potential of 0.72 V and an onset potential of 0.88 V with high stability in acidic environment.Very importantly, the different findings are correlated to one another, thereby establishing a composition to function relationship to provide a pathway for the integrated engineering of novel structures with improved performance. Acknowledgments Funding from the Operational Program “Competitiveness, Entrepreneurship & Innovation” (EPAnEK), NSRF 2014-2020 through the project Solar2HyP Τ2ΕΔΚ-01877 References [1] L. Osmieri, et al., Current Opinion in Electrochemistry 25 (2020) 100627.[2] T. Asset, et al., Joule 4 (2019) 33-44.[3] Jin-Cheng Li et al., Asia Materials 10 (2018) e461[4] Nan Zhang et al., Energy Environ. Sci. 13 (2020) 111-118 Figure 1

Modulation of Phase Transition in Cobalt Selenide with Simultaneous Construction of Heterojunctions for Highly-Efficient Oxygen Electrocatalysis in Zinc-Air Battery.

Phase transformation of cobalt selenide (CoSe2 ) can effectively modulate its intrinsic electrocatalytic activity. However, enhancing electroconductivity and catalytic activity/stability of CoSe2 still remains challenging. Heterostructure engineering may be feasible to optimize interfacial properties to promote the kinetics of oxygen electrocatalysis on a CoSe2 -based catalyst. Herein, a heterostructure consisting of CoSe2 and cobalt nitride (CoN) embedded in a hollow carbon cage is designed via a simultaneous phase/interface engineering strategy. Notably, the phase transition of orthorhombic-CoSe2 to cubic-CoSe2 (c-CoSe2 ) accompanied by in situ CoN formation is realized to build the c-CoSe2 /CoN heterointerface, which exhibits excellent/highly stable activities for oxygen reduction/evolution reactions (ORR/OER). Notably, heterostructure can modulate the local coordination environment and increase Co-Se/N bond lengths. Theoretical calculations show that Co-site (c-CoSe2 ) with an electronic state near Fermi energy level is the main active site for ORR/OER.Energetical tailoring of the d-orbital electronic structure of the Co atom of c-CoSe2 in heterostructure by in situ CoN incorporation lowers thermodynamic barriers for ORR/OER. Attractively, a zinc-air battery with a c-CoSe2 -CoN cathode displays excellent cycling stability (250h) and charge/discharge voltage loss (0.953/0.96V). It highlights that heterointerface engineering provides an option for modulating the bifunctional activity of metal selenides with controlled phase transformation.

Industrially Promising β‐Ni(OH)2 Nanosheets Self‐Supported Electrode for Highly Efficient Electrooxidation of 5‐Hydroxymethylfurfural

AbstractThe electrocatalytic selective oxidation of 5‐hydroxymethylfurfural (HMF) presents a highly efficient and eco‐friendly method for biomass utilization. Herein, we synthesized pure β‐Ni(OH)2 and amorphous Ni(OH)2 on nickel foam (NF) using a facile stepwise electrodeposition technique and evaluated their catalytic performances for the oxidation of HMF to 2,5‐furan dicarboxylic acid (FDCA). The β‐Ni(OH)2 nanosheets‐decorated electrode (β‐NiNS/NF) exhibited excellent interfacial lattice matching with the substrate nickel, resulting in enhanced electron transfer at the catalyst‐substrate interface, as confirmed by electrochemical analysis. Consequently, the β‐NiNS/NF electrode displayed improved intrinsic electrocatalytic activity and interfacial stability. Additionally, it demonstrated effective HMF adsorption capability. These advantageous properties led to enhanced HMF conversion, selectivity, and structural stability. Notably, the β‐NiNS/NF electrode achieved an unprecedented FDCA yield of 80.6 % under relatively large current density galvanostatic electrolysis commonly used in industry. Moreover, our investigation identified a novel possible oxidation pathway during HMF electrocatalysis. This study not only showcases an efficient and scalable synthetic approach but also highlights the potential of the β‐NiNS/NF electrode for industrial HMF electrocatalytic oxidation under conditions involving relatively large applied currents.

Cobalt-Iron Cyanometallates as Active Components for Water Electrolysis through Oxygen Evolution in Acid Medium

Electrochemical water splitting (oxidation) leading to the oxygen evolution at anode and hydrogen generation at cathode is a topic of growing scientific and technological interest. The reaction provides not only means for producing oxygen but, more importantly, for generation of highly pure hydrogen, a carrier for storing renewable energy and further utilization in low-temperature fuel cells. Among important issues are choice of the catalytic material, its morphology and operating conditions including temperature, electrolyte, pH etc. In some cases of electrolysis cells, at cathode, the hydrogen evolution could be accompanied by CO2-reduction (to simple organic molecules), regardless of water oxidation, at anode.The suitability of polynuclear mixed-valence inorganic materials (e.g. polyoxometallates, infinite metal oxides, cyanometallates) for the preparation of thin electrocatalytic films on electrode surfaces has been recognized in recent years. Among such systems, Prussian Blue (iron hexacyanoferrate) and the metal-substituted (e.g. with Co, Ni, or Ru) analogues known as transition metal cyanometallates have received considerable attention owing to their physicochemical stability, well-defined redox transitions, counter-ion-sorption selectivity and catalytic electroactivity. In the present work, we explore Prussian-Blue-like cobalt(II,III) hexacyanoferrate(II,III) cocatalytic overlayers together with ruthenium oxide (conventional electrocatalysis) and tungsten oxide n-type semiconductors (photoelectrochemistry). While cobalt hexacyanoferrate has already been demonstrated to exhibit some activity toward oxidation of water under photoelectrochemical conditions, its intrinsic electrocatalytic activity is unclear, and it will be addressed during presentation.The mixed, or multi-layered, cyanometallates of cobalt, ruthenium and were fabricated through electrodeposition in the appropriate mixtures for modification. Special attention was paid to their morphological, structural properties and the presence of counter-cations (e.g., potassium or sodium, in addition to protons). Electrochemical measurements were performed using cyclic voltammetry, chronoamperometry and chronocoulometry. The systems’ structural modifications as well as their effect on the electroactivity of the catalytic systems towards the oxygen evolution reaction in acid media were addressed. It is noteworthy that some of the hybrid cobalt-ruthenium hexacyanoferrate compositions showed remarkable catalytic ability towards the oxygen evolution reaction in acid electrolyte. In other words, the cyanide-linked ruthenium-oxo species was used to promote oxygen evolution while cobalt hexacyanoferrates acted as stabilizing agents. The enhanced catalytic activities of the as-synthesized electrodes should also be attributed to such features as high population of hydroxyl groups and high Broensted acidity (due to presence of Ru or W oxo sites) and related fast electron transfers coupled to unimpeded proton displacements. The possibility of metal-metal interactions between nanosized metals (Co and Ru or Co and W) cannot be excluded.

(Invited) Toward Rigorous Modeling of Metal-Metal, Metal-Oxide and Oxide-Oxide Interfaces for the Electrochemical Oxygen Cycle

To achieve Net-Zero Emissions by 2050, hydrogen and hydrogen fuel cells will play a significant role in powering vehicles. In this presentation, I will show, through first-principles-based modeling, how to achieve rigorous modeling of solid-solid interface for the hydrogen and oxygen evolution reactions in electrolysis and the oxygen reduction reaction in fuel cells; and how the fundamental understanding paves the way toward developing both model electrocatalysts and industrial electrocatalysts with significantly improved performance. Specifically, I will introduce the following three topics.[1] metal-metal interfaces: strain evolution and strain tuning of epitaxial, stepped and free-standing platinum group metals for the oxygen reduction reaction in fuel cells.(1)[2] metal-oxide interfaces: stability and activity of monolayer oxide/Pt interface toward improving the hydrogen evolution reaction in alkaline conditions.(2)[3] oxide-oxide interfaces: self-consistent modeling of active phases, reaction centers, and catalytic mechanisms of Ni- and Co-based layered double hydroxides for the oxygen evolution reaction.(3, 4) L. Wang, Z. Zeng, W. Gao, T. Maxson, D. Raciti, M. Giroux, X. Pan, C. Wang, J. Greeley, Tunable intrinsic strain in two-dimensional transition metal electrocatalysts. Science 363, 870-874 (2019).Z. Zeng, K.-C. Chang, J. Kubal, N. M. Markovic, J. Greeley, Stabilization of ultrathin (hydroxy)oxide films on transition metal substrates for electrochemical energy conversion. Nature Energy 2, 17070 (2017).F. Dionigi, Z. Zeng, I. Sinev, T. Merzdorf, S. Deshpande, M. B. Lopez, S. Kunze, I. Zegkinoglou, H. Sarodnik, D. Fan, A. Bergmann, J. Drnec, J. F. d. Araujo, M. Gliech, D. Teschner, J. Zhu, W.-X. Li, J. Greeley, B. R. Cuenya, P. Strasser, In-situ structure and catalytic mechanism of NiFe and CoFe layered double hydroxides during oxygen evolution. Nature Communications 11, 2522 (2020).F. Dionigi, J. Zhu, Z. Zeng, T. Merzdorf, H. Sarodnik, M. Gliech, L. Pan, W.-X. Li, J. Greeley, P. Strasser, Intrinsic Electrocatalytic Activity for Oxygen Evolution of Crystalline 3d-Transition Metal Layered Double Hydroxides. Angew. Chem., Int. Ed. 60, 14446-14457 (2021). Figure 1

Lattice Strain and Surface Activity of Dislocation‐Distorted AgPd Nanoalloys Under Preoxidation and Catalysis Condition

Although line defects endow excellent catalytic performance by undercoordinated sites with compressive tensile strain, few studies have systematically unraveled the relationship between dislocation, strain, and electrochemical activity for formate oxidation reactions (FOR). Herein, a novel approach for synthesizing defect‐rich nanomaterials at room temperature is proposed for the first time. The heated and dealloyed AgPd nanoparticles (hd‐AgPd NPs) substantially improve the intrinsic electrocatalytic activity by introducing compressive strain to tune its electronic structure. Electrochemical experiments show that the mass activity of hd‐AgPd NPs for FOR is 5.3 times higher than that of pure Pd nanoparticle catalysts. Following a 3600 s chronoamperometric process, a portion of the dislocation vanishes, but the strain persists on the AgPd (111) facet. The mechanisms for activity enhancement are further explored through density functional theory and molecular dynamics calculations, which show that compressive strain effectively alters its electronic structure and decreases the energy of the rate‐determining step during the reaction, significantly enhancing the FOR performance and stability. The results of electrochemical performance and physical characterization show that lattice strain has a more significant impact on FOR performance than alloying and preoxidation. This study presents a new approach to produce high‐performance catalysts by inducing strain into nanoparticles.

Study on density functional theory of MFe2O4 (M=Co, Ni, Cu) for electrocatalytic hydrogen and oxygen evolution reaction

The use of noble metals such as platinum (Pt) in electrocatalysts for oxygen and hydrogen evolution reactions has been studied for many years. However, the related electrocatalytic activity must be on par with Pt-based electrodes because of their high cost. Therefore, an attempt is made to find a low-cost alternative material that can show good electrocatalytic performance. In this work, we focused on M-Fe2O4 (M = Co, Ni, and Cu) as a potential electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) and theoretically studied it. As per our knowledge, no research regarding the theoretical investigation of an HER and OER electrocatalytic association with M-Fe2O4 is reported. This work is a simulation-based study on density functional theory to examine the combined electrocatalytic activity of M-Fe2O4 for HER and OER. The properties of the HER and OER processes, including the density of states, binding energies, band structure, charge transfer, and minimum-energy path, are studied and discussed. It is discovered that the energy barrier of the HER activity was computed lower in Ni-Fe2O4 is 0.046 eV, and the low computed energy barrier for OER in Co-Fe2O4 of 98 mV, irrespective of how it is set up. As a result, the study makes a detailed prediction that the suggested structure enhances MFe2O4's intrinsic electrocatalytic activity.