Evolution Reaction Performance Research Articles

Hierarchical NiCo2Se4 Arrays Composed of Atomically Thin Nanosheets: Simultaneous Improvements in Thermodynamics and Kinetics for Electrocatalytic Water Splitting in Neutral Media.

The inefficiency of electrocatalysts for water splitting in neutral media stems from a comprehensive impact of poor intrinsic activity, a limited number of active sites, and inadequate mass transport. Herein, hierarchical ultrathin NiCo2Se4 nanosheets are synthesized by the selenization of NiCo2O4 porous nanoneedles. Theoretical and experimental investigations reveal that the intrinsic hydrogen evolution reaction (HER) activity primarily originate from the NiCo2Se4, whereas the high oxygen evolution reaction (OER) performance is related to the NiCoOOH due to the structural reconstruction. The abundant Se and O vacancies introduced by atomically thin nanostructure modulate the electronic structure of NiCo2Se4 and NiCoOOH, thereby improving the intrinsic HER and OER activities, respectively. COMSOL simulation demonstrate the edges of extended nanosheets from the main body significantly promote the charge aggregation, boosting the reduction and oxidation current during HER/OER process. This charge aggregation effect notably exceeds the tip effect for the nanoneedle, highlighting the unique advantage of the hierarchical nanosheet structure. Benefiting from abundant vacancies and unique nanostructure, the hierarchical ultrathin nanosheet simultaneously improve the thermodynamics and kinetics of the electrocatalyst. The optimized samples display an overpotential of 92mV for HER and 214mV for OER at 100mA cm-2, significantly surpassing the performance of currently reported HER/OER catalysts in neutral media.

Revealing the characteristics of oxygen evolution reaction performance of NiZn ferrites

Magnetic field-assisted method has been proved as an effective method to improve oxygen evolution reaction performance (OER) of water splitting, however, the essential reason for the improvement of OER performance still remains unclear. Herein, Ni1-xZnxFe2O4 ferrites were prepared by the combination of hydrothermal and calcination method, the magnetic properties, oxygen evolution reaction performance and the effect of applied magnetic field on OER performance were studied and discussed according to the magnetic properties and ion site situation. The magnetic field effect depended on the applied magnetic field strength and the magnetic magnetization density of catalysts, it was attributed to changes of electron state and redistribution of ions in the spinel structure. The overpotential decreased by approximately 50 mV and its double layer capacitance increased about 60 % at 125 mT applied magnetic field. The results provided a newness research view for the domain of electrochemistry.

Ce-anchored NiFeOOH derived from in-situ self-optimization for efficient and highly durable water oxidation

Metal-organic frameworks could undergo surface reconstruction to form (oxy)hydroxide which is regarded as a real active species during the electrolysis. However, it is still a challenge to manipulate the reconstruction process to achieve the highly active (oxy)hydroxide species. Herein, a viable Ce decoration strategy is developed to optimize the structural reconstruction of NiFe-MIL-53 and enhance the activity of reconstructed species. Theoretical and experimental investigations suggest that the unique 4f valence electron structure of Ce atoms induces charge redistribution through strong 3d-2p-4f orbital electron coupling. This promotes the interface charge transfer, optimizes the adsorption of oxygen-containing intermediates, and reduces the energy barrier of rate-determining step, thus enhancing oxygen evolution reaction (OER) performance. Consequently, the reconstructed Ce@NiFeOOH requires a low overpotential of 219 mV at 10 mA cm−2 with a small Tafel slope of 28.1 mV dec−1. Additionally, Ce@NiFeOOH is also operated for 1780 h at 10/100 mA cm−2 without noticeable attenuation, demonstrating excellent long-term durability. This study offers a promising strategy for the construction of outstanding performance electrocatalysts.

MXenes as Electrocatalysts for Energy Conversion Applications: Advances and Prospects

Hydrogen as a potential future energy source provides a number of benefits in terms of sustainability, high energy density, and zero emissions. The production of hydrogen via water splitting is regarded as the cleanest and sustainable process. In contrast, fossil fuel combustion causes significant environmental problems through the production and release of secondary gases such as NOx, SO2, and CO2. It is vital to focus on reducing these harmful gases. CO2, a major pollutant produced by the combustion of fossil fuels and various human activities, plays a central role in the greenhouse effect and contributes to global warming. It is therefore imperative to actively eliminate and mitigate CO2 levels to preserve the global environment. MXenes and MXene‐based catalysts exhibit both outstanding hydrogen evolution reaction (HER) performance and CO2 reduction. In this review, recent progress is systematically examined and discussed in the preparation and utilization of MXenes as catalysts for HER and carbon dioxide reduction reaction (CO2RR). The discussion begins with a concise overview of the fabrication and characteristics of MXenes, followed by a comprehensive exploration of their efficacy as catalysts for HER and CO2RR.

Synergetic engineering of ZnS/In2Te3 heterostructure for efficient oxygen evolution reaction

AbstractThe potential of electrochemical water splitting to tackle energy and environmental issues has garnered substantial interest. In the present work, an effective ZnS/In2Te3 has been constructed by hydrothermal support on a stainless‐steel strip and explored for oxygen evolution. The addition of ZnS modifies the band structure of In2Te3 and enhances its specific conductivity and capacitance on an intrinsic level, making rapid ion transportation. The optimized ZnS/In2Te3 displayed efficient oxygen evolution reaction (OER) performance with an overpotential of 228 mV and a Tafel slope of 111 mV dec−1 with cyclic activity up to 1000 cycles in 1 M KOH solution. ZnS/In2Te3 has a large surface area (28 m3g−1) and a charge capacitance of (.037 mF), according to studies using Brunauer–Emmett–Teller and double‐layer capacitance. Combining several strategies improves overall electrochemical performance of ZnS/In2Te3, making it a promising option for use in state‐of‐the‐art OER.

Enhancing the acidic oxygen evolution reaction performance of RuO2-TiO2 by a reduction-oxidation process

As a promising alternative to Ir based acidic oxygen evolution reaction (OER) catalysts, Ru suffers from severe fading issues. Supporting it on robust oxides such as TiO2 is a simple and effective way to enhance its lifetime. Here, we find that a simple reduction-oxidation process can further improve both activity and stability of RuO2-TiO2 composites at high potentials. In this process, the degree of oxidation was carefully controlled to form Ru/RuO2 heterostructure to improve OER activity. Moreover, due to the oxophilicity difference of Ru and Ti, the structure of catalysts was changed from supported to embedded, which enhanced the protective effect of TiO2 and mitigated the dissolution of Ru element in acidic electrolyte, making as-prepared Ru/RuO2-TiO2 with better durability at all tested potentials.

Structure and oxygen evolution reaction performance of Ni-supported catalysts based on steam-exploded poplar

Using renewable steam-exploded poplar (SEP) as carbon source, nickel metal doped carbon hybrid materials were designed to synthesize catalysts (Ni/SEP) with certain oxygen evolution reaction (OER) properties and were compared with nickel catalysts supported on metal organic framework structure (ZIF67-Ni). The roles of SEP support in Ni-based catalyst were considered. Scanning electron microscope (SEM) images confirmed that the fiber could better hinder the aggregation of metal particles. Fourier transform infrared spectroscopy (FT-IR) indicated the presence of surface OH groups after the reduction process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the major form of metallic Ni in the resulting Ni catalysts. Carbon materials as carriers, the synergetic effect of Ni-doped, and carbon carrier played an important role in facilitating the kinetics of OER, which was similar to the carrier of metal-organic frame material. Notably, the Ni/SEP (11.3 mF/cm-2) and ZIF67-Ni (37.2 mF/cm-2) with better OER performance exhibited a smaller double layer capacitances (Cdl), suggesting the intrinsic OER catalytic activity of the Ni/SEP and ZIF67-Ni were much higher in comparison to the ZIF67-Ni/SEP. Moreover, the inferior performance of Ni/SEP further indicated that the synergistic effect between carbon and Ni/NiO contributes to the enhanced OER activity.

Unveiling the potential of a g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction photocatalyst for rechargeable zinc-air battery: Visible-light-driven photo-assisted charging for bifunctional ORR and OER at the air cathode

Advancements in solar-driven energy storage technology have been achieved for rechargeable zinc-air batteries (RZABs), facilitating accelerated kinetic responses in both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, we successfully synthesized a novel g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction through a facile hydrothermal process, demonstrating its efficacy as a bifunctional photocatalyst. Upon exposure to LED irradiation, this heterojunction triggers an effective separation of the photogenerated electron-hole pairs, resulting in enhanced oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance by 46.19 % and 65.69 % respectively, compared to non-LED conditions. Interestingly, the reduction in the potential gap under LED irradiation (0.06 V), correlating with a significant 2.71 % increase in round-trip efficiency (RTE), is observed. In addition, the optimized band alignment derived from g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction for photo-assisted charging rechargeable zinc-air batteries is proposed. Insightfully, photo-enhanced charging in RZABs mechanism during the charge/discharge process through in-situ X-ray absorption spectroscopy (XAS) is monitored, confirming the large interaction between O2 adsorption and Bi 6d orbitals of g-C3N4/BiOBr/Bi2O2CO3 in the presence of LED. In conclusion, our innovative g-C3N4/BiOBr/Bi2O2CO3 ternary heterojunction underscores the significant role that visible-light-driven photocatalysts can play in enhancing the efficiency of rechargeable zinc-air batteries.

Formation of ferromagnetic Fe5Se8 via phase transition and enhanced hydrogen evolution reaction with alternating magnetic fields

Leveraging alternating magnetic fields (AMFs) to induce localized heating in catalysts has emerged as a powerful approach to boost electrocatalytic reactions. However, the rational design and synthesis of ferromagnetic catalysts that can be stably coupled with an AMF to improve the hydrogen evolution reaction (HER) performance are still urgent and challenging. Herein, the ferromagnetic triclinic Fe5Se8 has been realized through the phase transition from nonmagnetic orthorhombic FeSe2 synergistically triggered by the selenium vacancies and the strain engineering, making it a good candidate for AMFs-assisted HER. Experimental results and theoretical calculation demonstrate that the phase transition-prepared ferromagnetic Fe5Se8 exhibits much better HER performance than nonmagnetic FeSe2. More importantly, under high-frequency AMF stimulation, the HER performance of ferromagnetic Fe5Se8 is greatly enhanced (the overpotential decreased by 63 mV), which is mainly attributed to the localized magnetic heating effect. This study realizes the controlled phase transition synthesis of ferromagnetic catalysts, indicating that AMF is an effective approach to manipulate the performance of ferromagnetic catalysts.

Effect and mechanism of hydrogen annealing temperature on the HER performance of RuO2-based catalysts in acid media

Annealing as an experimental means is often used to treat various electrocatalysts for improving their hydrogen evolution reaction (HER) performance. Herein, in order to investigate the effect of hydrogen annealing temperature on the HER performance of RuO2-based electrocatalysts, commercial RuO2, self-synthesized RuO2, and self-synthesized RuO2/MoO3 composite are annealed at 150, 300, 500, and 700 °C in a hydrogen atmosphere, respectively. It's found that RuO2 is gradually deduced at 150 °C, ultimately, completely reduced to Ru under 300 °C. Meanwhile, the content of RuO2 at the samples surface is gradually decreases as the annealing temperature increase to 700 °C. However, for all samples, the 500 °C annealed sample shows the best HER performance in acid solutions, including the lowest over potential, the smallest Tafel slope, and the largest double-layer capacitance. We inferred that the optimal HER performance of the 500 °C annealed samples maybe attributed to their appropriate Ru/RuO2 ratio. Density functional theory (DFT) calculations reveal that significant electron transfer across the Ru/RuO2 interface, thereby optimizing the adsorption free energy of H on Ru and RuO2, ultimately resulting in Ru/RuO2 catalyst exhibiting better HER activity than bare Ru and RuO2. The study provides guidance on the preparation of RuO2-based electrocatalysts for achieving efficient hydrogen evolution.

Manipulating the morphology and charge accumulation driven- Schottky functionalized type II-scheme heterojunction for photocatalytic hydrogen evolution and SERS detection

Inspired by energy conversion and sensing strategies, the construction of a type-II heterojunction proves advantageous in enhancing interfacial charge transfer, redox capabilities, and sensitive detection. Herein, we have developed as-prepared a hierarchical heteronanostructure composed of 2D ultrathin g-C3N4 (g-CN) nanosheets, 3D SrTiO3 (STO) nanocubes, and Ag plasmonic nanoparticles (NPs) with a well-controlled configuration and intimate contact for improved practical applications. This multifunctional heterojunction not only exhibits outstanding hydrogen evolution reaction (HER) performance but also shows excellent SERS detection. The creation of hybrid morphologies and type II schemes contributes to expanding visible light absorption and shortening the path of charge carrier transition. The ternary sample also exhibits an efficient photocatalytic HER rate of 9378 μmol g−1 h−1, which is 13.3 and 26.3 times higher than that of STO (703 μmol g−1 h−1) and g-CN (356 μmol g−1 h−1), respectively. Photoluminescence spectroscopy and linear sweep voltammetry (LSV) measurements suggest that the synergistic effect among g-CN nanosheets, STO nanocubes and Ag contributes to enhanced charge separation, as indicated by the applied potential of −0.9 V vs. saturated Ag/AgCl to obtain a photocurrent density of −15 mA cm−2 for the HER. The obtained STO/g-CN/Ag sample exhibits significant capability in enriching small molecules, facilitating the determination of organic pollutants even at ultralow concentrations. Additionally, it exhibits impressive SERS sensitivity and photocatalytic performance. Crystal Violet (CV) at low concentrations can be distinguished and undergoes almost complete degradation under visible-light illumination. The detection platform exhibits ultralow detection capability down to 10−10 M for CV. The outstanding SERS detection may be assigned to the combined enrichment abilities of g-CN, STO and the localized surface plasmon resonance (LSPR) of Ag NPs. Furthermore, the type-II heterojunction of the ternary photocatalyst and the mechanisms governing charge carrier flow and transfer on the conductive Ag co-catalyst were also investigated. This work provides novel insights and techniques for effectively engineering 3D STO-like semiconductors, facilitating both green energy production and the detection of trace molecules.

In-situ construction of RuS2 nanocrystal-decorated amorphous NiSx nanosheets for industrial-current-density water splitting

Developing enabling electrocatalysts for water splitting to operate at industrial-current-density is crucial for large-scale hydrogen production. Herein, a facile wet-chemistry strategy and scalable in-situ sulfidation technique are designed for formation of RuS2 nanocrystal-decorated amorphous NiSx nanosheets vertically aligned on Ni foam (NF) (RuNiSx/NF) as ultra-highly efficient electrocatalysts for electrochemical water splitting (EWS). The optimized electrocatalyst exhibits an excellent hydrogen evolution reaction (HER) performance, requiring overpotentials of only 15, 50, and 114 mV at 10, 100, and 1000 mA/cm2, respectively, with robust stability at 10, 100, and 500 mA/cm2 for 120 h, ranking it one of the efficient electrocatalysts for industrial water electrolysis. The electron redistribution over heterointerfaces induces the modulatory electronic states of heterostructures, thus leading to the favorable adsorption behavior for reaction intermediates, enhancing intrinsic activity of active sites. Impressively, a RuNiSx/NF||RuNiSx/NF EWS device can afford industrial current densities of 10, 100, and 500 mA/cm2 at voltages of 1.55, 1.77, and 2.35 V, respectively, together with robust durability for over 50 h (@1000 mA/cm2). This work provides an innovative approach to design unique heterostructures for industrial EWS via modulatory electronic states.

Metal-Organic-Framework-Derived Nitrogen-Doped Carbon-Matrix-Encapsulating Co0.5Ni0.5 Alloy as a Bifunctional Oxygen Electrocatalyst for Zinc-Air Batteries.

The development of low-cost, high-performance oxygen electrocatalysts is of great significance for energy conversion and storage. As a potential substitute for precious metal electrocatalysts, the construction of efficient and cost-effective oxygen electrocatalysts is conducive to promoting the widespread application of zinc-air batteries. Herein, CoxNiyMOF nanoparticles encapsulated within a carbon matrix were synthesized and employed as cathode catalysts in zinc-air batteries. Co0.5Ni0.5MOF exhibits superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance and durability. The zinc-air battery assembled with Co0.5Ni0.5MOF as the air cathode exhibits a maximum power density of 138.6 mW·cm-2. These improvements are mainly attributed to the optimized metal composition of the cobalt-nickel alloy, which increases the specific surface area of the material and optimizes its pore structure. Significantly, the optimization of the electronic structure and active sites within the material has led to amplified ORR/OER activity and better zinc-air battery performance. This study underscores the immense promise of Co0.5Ni0.5MOF catalysts as feasible substitutes for commercial Pt/C catalysts in zinc-air batteries.

Spectroscopic Investigations of Complex Electronic Interactions by Elemental Doping and Material Compositing of Cobalt Oxide for Enhanced Oxygen Evolution Reaction Activity

AbstractDoping and compositing are two universal design strategies used to engineer the electronic state of a material and mitigate its disadvantages. These two strategies are extensively applied to design efficient electrocatalysts for water splitting. Using cobalt oxide (CoO) as a model catalyst, it is proven that the oxygen evolution reaction (OER) performance can be progressively improved, first by Fe‐doping to form Fe‐CoO solid solution, and further by the addition of CeO2 to produce a Fe‐CoO/CeO2 composite. X‐ray absorption spectroscopy (XAS) reveals that distinct electronic interactions are induced by the processes of doping and compositing. Fe‐doping of CoO can break down the structural symmetry, changing the electronic structure of both Co and O species at the surface and decreasing the flat‐band potential (Vfb). In comparison, subsequent compositing of Fe‐CoO with CeO2 induces negligible electronic changes in the Fe‐CoO (as seen in ex situ characterizations), but significantly modifies the oxidative transformations of both Co and Fe under OER conditions. The spectroscopic investigations reveal that Fe‐doping and CeO2 compositing play different roles in modifying the electronic properties of CoO in its pristine state and during OER catalysis, in return, providing useful guidance for the design of more efficient electrocatalysts using these two strategies.

Ce-4f as an electron-modulation reservoir weakening Fe-O bond to induce iron vacancies in CeFevNi hydroxide for enhancing oxygen evolution reaction

Designing novel rare-earth-transition metal composites is at the forefront of electrocatalyst research. However, the modulation of transition metal electronic structures by rare earths to induce vacancy defects and enhance electrochemical performance has rarely been reported. In this study, we systematically investigate the mechanism by which Ce-4f electron modulation weakens the Fe-O bond, thereby altering the electronic structure in CeFevNi hydroxide to improve oxygen evolution reaction (OER) performance. Theoretical calculations and experimental characterizations reveal that Ce-4f orbitals function as electron-modulation reservoirs, capable not only of retaining or donating electrons but also of influencing the material's electronic structure. Moreover, Ce-4f bands optimize the Fe lower Hubbard bands (LHB) and O-2p bands, leading to weakened Fe-O bonds and the formation of cationic vacancies. This change results in the upshift of the d-band center at the active sites, favoring the reaction energy barrier for oxygen intermediates in the OER process. The synthesized catalyst demonstrated an overpotential of 201 mV at 10 mA cm−2 and a lifetime exceeding 200 h at 100 mA cm−2 under alkaline conditions. This work offers a proof-of-concept for the application of the mechanism of rare earth-induced transition metal vacancy defects, providing a general guideline for the design and development of novel highly efficient catalysts.

Cost-efficient sunlight-driven thermoelectric electrolysis over Mo-doped Ni5P4 nanosheets for highly efficient alkaline water/seawater splitting

Thermoelectric water spitting to hydrogen systems has great potential in the production of environment-friendly fuel using renewable solar energy in the future. In this work, we prepared porous nanosheet Mo doping Ni5P4 catalysts on nickel foam with efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in alkaline media. Density Functional Theory (DFT) calculations and experimental studies have shown that Mo doping deadeneds the interaction between H and O atomic orbitals of transition state water molecules, effectively weakening the activation energy of H2O dissociation. Therefore, Mo doping is favorable for enhancing HER activity with overpotential at 10 mA cm–2 of 93 mV and Tafel slope of 40.1 mV dec–1 in 1 M KOH. Besides, it exhibits high alkaline OER activity with an ultra-low overpotential of 200 mV at 10 mA cm–2. Moreover, this catalyst only needs 1.537 V in a dual-electrode configuration of the electrolytic cell, which is much lower than the commercial Pt/C-RuO2 couple (1.614 V). In addition, we have developed and constructed a solar thermoelectric generator (TEG) that is capable of floating on water. This TEG has a continuous power output and an exceptionally long lifespan, providing a stable power supply to the synthesized catalyst electrolyzer. It can produce a maximum power output of over 90 mW, meeting the requirement of converting solar radiation heat into usable electricity. As a result, the system achieves productivity of 0.11 mL min–1 H2. This solar thermal energy conversion technology shows the possibility of large-scale industrial production of H2 and provides a new idea for exploring heat source utilization.

A robust and highly active bimetallic phosphide/oxide heterostructure electrocatalyst for efficient industrial-scale hydrogen production

Efficient and durable high-current-density bifunctional electrocatalysts are vital for cost-effective production of alkaline water electrolyzers (AWEs) on an industrial scale. However, existing commercial catalysts, such as Raney Ni which requires over 2.5 V for just 500 mA cm−2, fail to achieve high current densities with low cell voltages. In this study, we introduce a bifunctional RuP2/Ni5P4/NiMoO4 heterostructure electrocatalyst, synthesized via a facile hydrothermal method, followed by the controlled addition of ruthenium (Ru) and subsequent phosphorization. This process yielded (Ru, Ni) phosphides and NiMoO4 with a moderate weight percentage and mass loading of Ru content, approximately 1.02 wt% and 61 μg cm−2, respectively. The synergistic effect of these phosphides and bimetallic oxides significantly improves water dissociation, as well as the hydrogen and oxygen evolution reaction (HER and OER) performances. Under industrial conditions (80 °C and 6 M KOH), our catalyst achieves low overpotentials of 273 mV for HER and 390 mV for OER at 2000 mA cm−2, outperforming commercial Pt/C and RuO2 catalysts. Additionally, in an AWE, our catalyst maintains a low operating voltage of 1.76 V for 1 A cm−2, with consistent performance over 100 h at 500 mA cm−2. It records an electricity consumption of 3.97 kW h Nm−³ and an electrolyzer efficiency of 89.1%, underscoring its potential for cost-effective industrial applications. Furthermore, accelerated degradation tests under variable current loads show no significant change in cell voltage and high-frequency resistance (HFR), demonstrating robustness for intermittent energy sources. This work proposes a novel design principle for high-performance electrocatalysts, significantly reducing reliance on noble metals and offering a robust, efficient solution for industrial-scale hydrogen production.

Facile fabrication of nickel-cobalt oxide for efficient oxygen evolution reaction from ammonia leaching solution of spent lithium-ion batteries

Ammonia leaching has been gained considerable attention for its ability to selectively extract nickel and cobalt from spent ternary cathode material. Despite its efficacy, the subsequent recovery of ammonia leachate remains challenging. Herein, a short-process and sustainable method for the synthesis of nickel-cobalt oxide via ammonia evaporation of ammonia leachate and heat treatment of the resultant precursor has been proposed. The ammonia evaporation process, conducted at an evaporation temperature of 130 °C with hydrazine hydrate as a reducing agent, facilitated the precipitation of ∼95% Ni and ∼99% Co as a precursor. Subsequently, the effect of precursor roasting temperature on electrode material synthesis was systematically studied. The precursor was roasted at 300 °C to successfully synthesize nickel-cobalt oxide. Physical and electrochemical characterizations revealed that the nickel-cobalt oxide possesses a significant specific surface area of 161.150 m2/g, and exhibits excellent oxygen evolution reaction performance, evidenced by an overpotential of 350.7 mV at 10 mA/cm2 and a Tafel slope of 159.8 mV/dec. Overall, the proposed method not only promotes the recycling and utilization of ammonia reagents and mother liquor, but also introduces an innovative approach for the synthesis of nickel-cobalt oxide as an electrode material.

Porous TiN-based ceramic electrode with N-modified Co-based Nanorods/TiN heterointerfaces for efficient overall water splitting

The development of high-performance electrocatalytic electrodes for overall water splitting is a crucial issue to realize renewable hydrogen production. This paper presents the in situ growth of N-modified Co-based nanorods on porous TiN ceramic membranes using the hydrothermal method and thermal NH3 treatment, resulting in a novel self-supported electrocatalytic electrode with abundant heterointerfaces, denoted as NCTN-x-y (x: nitridation temperature; y: nitridation time). In the alkaline medium (1 M KOH), the NCTN-350-2 electrode displays the best hydrogen evolution reaction (HER) activity (ƞ10 = 66 mV), and the NCTN-250-3 electrode manifests the best oxygen evolution reaction (OER) performance (ƞ10 = 270 mV). Accordingly, these two electrodes comprise an electrolyzer, which features a current density of 10 mA cm−2 at a low cell voltage of 1.63 V. The good electrocatalytic performance can be attributed to the abundant heterointerfaces formed between the porous TiN ceramic membrane and the N-modified Co-based nanorods, in conjunction with the hierarchical pore structure of the TiN ceramic membrane. Theoretical calculations identify that the construction of heterointerfaces modulates the electronic structure of active sites, thereby promoting the dissociation of H2O, optimizing the H* adsorption energy (ΔGH*), and accelerating the reaction kinetics, which ultimately improve the electrocatalytic activity of electrode.

Heterophase Intermetallic Compounds for Electrocatalytic Hydrogen Production at Industrial-Scale Current Densities.

Heterophase nanomaterials have sparked significant research interest in catalysis due to their distinctive properties arising from synergistic effects of different components and the formed phase boundary. However, challenges persist in the controlled synthesis of heterophase intermetallic compounds (IMCs), primarily due to the lattice mismatch of distinct crystal phases and the difficulty in achieving precise control of the phase transitions. Herein, orthorhombic/cubic Ru2Ge3/RuGe IMCs with engineered boundary architecture are synthesized and anchored on the reduced graphene oxide. The Ru2Ge3/RuGe IMCs exhibit excellent hydrogen evolution reaction (HER) performance with a high current density of 1000 mA cm-2 at a low overpotential of 135 mV. The presence of phase boundaries enhances charge transfer and improves the kinetics of water dissociation while optimizing the processes of hydrogen adsorption/desorption, thus boosting the HER performance. Moreover, an anion exchange membrane electrolyzer is constructed using Ru2Ge3/RuGe as the cathode electrocatalyst, which achieves a current density of 1000 mA cm-2 at a low voltage of 1.73 V, and the activity remains virtually undiminished over 500 h.