Non-noble Metal Electrocatalysts Research Articles

In-situ growth of MoSe2 on N-doped Ti3C2Tx for electrocatalytic hydrogen evolution in alkaline media

Abstract Serious environmental contamination and the energy crisis have heightened public desire for new renewable energy sources. Because of its high energy content and non-polluting qualities, hydrogen energy has emerged as a viable alternative to fossil fuels. Currently, high-purity hydrogen is typically produced through water electrolysis. The sensible use of electrocatalysts in this process can significantly minimize power usage in the electrolysis of water, which is of great significance to industrial production. However, the electrocatalyst that is inexpensive, has abundant reserves and performs well has yet to be discovered, severely restricting the promotion and application of hydrogen energy. In this paper, a MoSe2/N-doped Ti3C2TX heterostructure with notable electrocatalytic hydrogen evolution activity in an alkaline environment was fabricated via nitrogen doping and in-situ growth of molybdenum selenide. When the current density is 10 mA·cm-2, its overpotential and Tafel slope are 321.87 mV and 139.97 mV·dec-1, respectively. This work serves as a valuable experimental reference for the development of non-noble metal electrocatalysts based on two-dimensional materials.

Promotion of the oxygen evolution reaction by introducing MoS2 into CoFe LDH via improved charge transfer and electrocatalytical activity

It is of great significance to investigate economical and efficient non-noble metal electrocatalysts for improving the kinetics of slow oxygen evolution reaction (OER). This study presents a hydrothermal method employed for the synthesis of MoS2@CoFe LDH/NF (NF: nickel foam) electrocatalysts. The layered structure of CoFe LDH offers abundant active sites for OER. The combined effects of MoS2 nanoparticles and LDH structure elevate the catalytic performance of OER. When the current density of 10 mA cm−2, the overpotential and Tafel slope were measured to be 234 mV and 87.68 mV dec-1. Moreover, the current density remained at 90 % of its initial value for 18 h in an alkaline solution, demonstrating excellent stability. Consequently, this study provides valuable insights for designing nanoparticle-LDH heterostructures to achieve resultful OER in practical applications.

Accelerating H* desorption of hollow Mo2C nanoreactor via in-situ grown carbon dots for electrocatalytic hydrogen evolution

Molybdenum carbide (Mo2C) is a promising non-noble metal electrocatalyst with electronic structures similar to Pt for hydrogen evolution reaction (HER). However, strong H* adsorption at the Mo sites hinders the improvement of HER performance. Here, we synthesized monodisperse hollow Mo2C nanoreactors, in which the carbon dots (CD) were in situ formed onto the surface of Mo2C through carburization reactions. According to finite element simulation and analysis, the CD@Mo2C possesses better mesoscale diffusion properties than Mo2C alone. The optimized CD@Mo2C nanoreactor demonstrates superior HER performance in alkaline electrolyte with a low overpotential of 57 mV at 10 mA cm−2, which is better than most Mo2C-based electrocatalysts. Moreover, CD@Mo2C exhibits excellent electrochemical stability during 240 h, confirmed by operando Raman and X-ray diffraction (XRD). Density functional theory (DFT) calculations show that carbon dots cause the d-band center of CD@Mo2C to shift away from Fermi level, promoting water dissociation and the desorption of H*. This study provides a reasonable strategy towards high-activity Mo-based HER eletrocatalysts by modulating the strength of Mo–H bonds.

Liquid metal-assisted solid-flame combustion synthesis of transition metal carbide nanocrystals for enhanced hydrogen evaluation reaction

Efficient hydrogen production relies on cost-effective and durable non-noble metal electrocatalysts for the hydrogen evolution reaction (HER). In this work, a liquid metal-assisted solid-flame combustion synthesis (SF-CS) method was used to create transition metal carbide TMC) nanocrystals with exposed facets. The TMCs include TiC, VC, NbC, TaC, Ta2C, WC, and Mo2C. In acidic solutions, the TMC nanocrystals show enhanced conductivity and superior HER performance, as evidenced by their lower Tafel slope, higher current density, and decreased overpotential. In particular, Mo2C nanocrystals exhibit an overpotential of 95 mV and a Tafel slope of 26 mV dec−1. These findings highlight a noteworthy improvement over previously reported nanostructures in recent years in terms of the HER properties of Mo2C with particular facets. This improvement is attributed to the unique surface characteristics, such as energy and active sites, which are impacted by various factors and require more investigation to meet the intended goals.

Vertical graphene nanowalls supported hybrid W2C/WOx composite material as an efficient non-noble metal electrocatalyst for hydrogen evolution

Research for the development of noble metal-free electrodes for hydrogen evolution has blossomed in recent years. Transition metal carbides compounds, such as W2C, have been considered as a promising alternative to replace Pt-family metals as electrocatalysts towards hydrogen evolution reaction (HER). Moreover, hybridization of TMCs with graphene nanostructures has emerged as a reliable strategy for the preparation of compounds with high surface to volume ratio and abundant active sites. The present study focuses in the preparation of tungsten carbide/oxide compounds deposited in a three-dimensional vertical graphene nanowalls (VGNW) substrate via chemical vapor deposition, magnetron sputtering and thermal annealing processes. Structural and chemical characterization reveals the partial carburization and oxidation of the W film sputtered on the VGNWs, due to C and O migration from VGNWs towards W during the high temperature annealing process. Electrochemical characterization shows the enhanced performance of the nanostructured hybrid W2C/WOx on VGNW compound towards HER, when compared with planar W2C/WOx films. The W2C/WOx nanoparticles on VGNWs require an overpotential of −252 mV for the generation of 10 mA cm−2. Chronoamperometry tests in high overpotentials reveal the compounds stability while sustaining high currents, in the order of hundreds of mA. Post-chronoamperometry test XPS characterization unveils the formation of a W hydroxide layer which favours hydrogen evolution in acidic electrolytes. We aspire that the presented insights can be valuable for those working on the preparation of hybrid electrodes for electrochemical processes.

From Atomic-Level Synthesis to Device-Scale Reactors: A Multiscale Approach to Water Electrolysis.

ConspectusThe development of an advanced energy conversion system for water electrolysis with high efficiency and durability is of great significance for a hydrogen-powered society. This progress relies on the fabrication of electrocatalysts with superior electrochemical performance. Despite decades of advancements in exploring high-performance noble and non-noble metal electrocatalysts, several challenges persist at both the micro- and macrolevels in the field of water electrolysis.At the microlevel, which encompasses electrocatalyst synthesis and characterization, design strategies for high-performance electrocatalysts have primarily focused on interface chemical engineering. However, comprehensive understanding and investigation of interface chemical engineering across various length scales, from micrometers to atomic scales, are still lacking. This deficiency hampers the rational design of catalysts with optimal performance. Under harsh reaction conditions, such as high bias potential and highly acidic or alkaline media, the surface of catalyst materials is susceptible to undergoing "reconstruction", deviating from what is observed through ex situ characterization techniques postsynthesis. Conventional ex situ characterization methods do not provide an accurate depiction of the catalyst's structural evolution during the electrocatalytic reaction, hindering the exploration of the catalytic mechanism.At the macrolevel, pertaining to catalysis-performance evaluation systems and devices, traditional laboratory settings employ a conventional three-electrode or two-electrode system to assess the catalytic performance of electrocatalysts. However, this approach does not accurately simulate hydrogen production under realistic industrial conditions, such as elevated temperatures (60-70 °C), high current densities exceeding 0.5 A cm-2, and flowing electrolytes. To address this limitation, it is crucial to develop testing equipment and methodologies that replicate the actual industrial conditions.In this Account, we propose a multiscale research framework for water electrolysis, spanning from microscale synthesis to macroscale scaled reactor design. Our approach focuses on the design and evaluation of high-performance HER/OER (hydrogen evolution reaction/oxygen evolution reaction) electrocatalysts, incorporating the following strategies: Leveraging principles of interface chemical engineering across various length scales (micrometers, nanometers, and atoms) enables the design of catalyst materials that enhance both activity and durability. This approach provides a comprehensive understanding of the intricate interplay between the catalyst structure and activity, implementing in situ/operando characterization techniques to monitor dynamic interfacial reactions and surface reconstruction processes. This facilitates a profound exploration of catalytic reaction mechanisms, offering insights into the catalyst's structural evolution during the electrocatalytic reaction. We construct a laboratory-scale membrane electrode assembly (MEA) electrochemical reactor capable of operating at high current densities (>1 A cm-2) to evaluate the electrocatalytic performance under simulated industrial conditions. This ensures objective and authentic assessments of the catalyst application potential. Throughout the following sections, we illustrate the application of interface chemical engineering on different length scales in designing diverse electrocatalyst materials. We rely on in situ characterization techniques to gain a profound understanding of the mechanisms behind the HER and OER. Additionally, we describe the development of both acidic and alkaline MEA electrochemical reactors to enhance the precision of electrocatalytic performance evaluation. Finally, we provide a concise overview of the challenges and opportunities in this field.

Nanoflowers Ni(OH)x/p-Ni with in-situ formation of high-valence nickel for boosting energy-saving hydrogen production from urea-assisted water splitting

Using urea oxidation reaction (UOR) instead of oxygen evolution reaction (OER) is one of promising strategies for significantly diminish power consumption for hydrogen production from electrochemical water splitting. The electrocatalysts with cost-effective, multifunctional and high-performance are urgently required for enhancing UOR and hydrogen evolution reaction (HER), but this remains a challenge. Herein, we designed a bifunctional Ni(OH)x/p-Ni catalyst by electrochemical oxidation of Ni(OH)2in-situ grown on the surface of porous Ni membrane (p-Ni) to generate more abundant high-valence Ni3+ active species, which is favorable for reducing the energy barrier of electrochemical reaction. At the same time, a large number of metallic oxygen bonds (Ni–O) were formed to optimize the reaction kinetics of the electrochemical process, thus promoting the overall urea electrolysis efficiency. In 1.0 M KOH with 0.3 M urea, the optimized Ni(OH)x/p-Ni only requires potentials of 1.38 V and 0.22 V to obtain a current density of 100 mA cm−2 for UOR and HER, respectively. Notably, by assembling the Ni(OH)x/p-Ni as the cathode and anode for hydrogen production from urea-assisted water splitting, it can drive a current density of 100 mA cm−2 at a low voltage of 1.52 V and has excellent stability. This work provides a feasible strategy for design efficiently non-noble metal electrocatalysts for energy-saving hydrogen production and purifying urea-rich wastewater.

Facile synthesis of amorphous/crystalline Ni-Fe thiophenedicarboxylate coordination polymer nanobelts for efficient water oxidation

The oxygen evolution reaction (OER) is a complex four-electron transfer process that poses a significant challenge to the efficient production of hydrogen through water splitting. However, developing non-noble metal electrocatalyst with excellent OER performance is still a big challenge. Herein, we propose a new strategy for the in-situ growth of two-dimensional amorphous/crystalline thiophene-based Ni-Fe metal–organic frameworks (MOFs) using Ni-Fe foam (NFF) as metal source and current collector, and thiophene-2,5-dicarboxylic acid (TDC) as corrosion agent and ligand. TDC was ionized at high temperature to produce H+ ions that etch NFF to release Ni2+ and Fe2+ ions, which were coordinated with TDC to in situ synthesize two-dimensional Ni-Fe thiophenedicarboxylate coordination polymer (NiFe-TDC) nanobelts on NFF. The unique structure and synergistic effect of Ni and Fe ions of NiFe-TDC0.05 result in the excellent OER performance with an overpotential of 224 and 256 mV at current densities of 10 and 100 mA cm−2, respectively, and it can run stably for 100 h at a current density of 100 mA cm−2, indicating the outstanding stability. Furthermore, NiFe-TDC0.05 remains the excellent OER performance with an extremely low potential of 196 and 271 mV at current densities of 10 and 100 mA cm−2 in seawater with 1 mol L-1 (M) KOH, respectively. The assembled NiFe-TDC0.05 || Pt/C water electrolysis cell achieves a current density of 100 mA cm−2 at a low voltage of 1.78 V. The work provides a new method to prepare two dimensional MOFs for efficient water oxidation.

Porous high-entropy alloy coatings as highly efficient electrocatalysts for electrocatalytic water splitting

Developing highly efficient and stable non-noble metal electrocatalysts has always been a grand challenge for water splitting. Herein, the promising and highly efficient porous high entropy alloy (HEA) coatings is fabricated through the plasma spraying, which could be favorable to solve the above issues. Abased on the synergistic effect of different metals and the porous structure within the HEA coatings, it can provide the superior catalytic activities. Hence, the CoCrFeNiMo catalyst displays a low overpotential of 273 mV (for oxygen evolution reaction, OER) at 100 mA cm−2 in 1.0 M KOH electrolyte. As hydrogen evolution reaction (HER) catalysts, the CoCrFeNiMo presents a small overpotential. When the catalysts can be utilized to the overall water splitting, it delivers an excellent durable for 24 h. DFT result shows that CoCrFeNiMo is conducive to the hydrogen adsorption/desorption process, and it can enhance the transformation of *O to *OOH and improve the OER performance. This study not only offers a universal method to prepare high performance electrocatalysts, but also demonstrates the great potential of HEA coatings in energy conversion fields.

Development of metal free biochar based material for water electrolysis hydrogen production using anion exchange membrane: Creating circular economy

In recent days, a steady growth is being noted in hydrogen energy field owing to the global rise in population and increased energy demand. Fast depletion of fossil-based fuels and climate change issues are driving nations towards exploring an alternate energy resource. Hydrogen energy is one such an option owing to availability of simple and cost intensive technology involvement. Alkaline water electrolysis is one of the simplest ways of producing hydrogen utilizing renewable energy and oxygen as the only byproduct thus not contributing to carbon footprint. However, immediate attention is needed to minimize the cost of electrolyzer components, maintenance and energy. Commercial proton exchange membrane water electrolyzers (PEM) in market employ large capital cost due to high-priced Nafion and other PFSA membranes, titanium endplates and noble metal-based electrocatalysts. As a consequence, researchers are looking into the usage of Anionic exchange membrane (AEM) for water/alkali based electrolyzer for producing hydrogen with non-noble metal electrocatalysts and low-cost metal end plates. In this article a waste coconut shell derived biochar is explored as the carbon matrix for base of electrocatalysts to replace other high-cost carbon support for electrocatalyst in water electrolyzer. The structural and electrical properties of the coconut shell biochar are studied and compared with other available carbon supports. To deep drive in the electrolyzer performance this approach is further extended to MEA (Membrane Electrode Assembly) level to study the metal free electrocatalyst behavior in real-time environmental conditions.

Ultrafast room-temperature construction of hierarchical hollow rodlike nanoarrays based on amorphous NiFeCo layered double hydroxide toward enhanced oxygen evolution reaction

Designing and constructing non-noble metal electrocatalysts with high catalytic activity for oxygen evolution reaction (OER) is a significant challenge for energy storage and conversion. Transition-metal-based layered double hydroxides (LDHs) are the most efficient OER catalysts. However, their catalytic performance and commercial application are limited by their small electrochemical active areas and poor electronic conductivity. Herein, hollow hierarchical rodlike nanoarrays on nickel foam assembled with amorphous NiFeCo-LDH nanosheets were prepared using a metal–organic framework, ZIF-67, as a sacrificial template by a facile and ultrafast ion-exchanged reaction at room temperature. The as-prepared electrocatalyst possessed a large specific surface area (397 m2/g), unique structure, fast charge transfer and abundant active sites, and thus displayed a superior performance for OER with a low overpotential of 202 mV at 10 mA/cm2, a Tafel slope of 47.9 mV/dec and long-term durability in 1.0 M KOH electrolyte. This research affords a facile strategy to rationally design high activity electrocatalysts of multi-metallic LDHs for OER.

Interfacial engineering of Ni-Co-Mn@Ni nanosheet-nanocone arrays as high performance non-noble metal electrocatalysts for hydrogen generation.

The electrochemical hydrogen production from water splitting is a promising strategy for obtaining new energy sources and replacing fossil fuels. In this study, nickel nanocones were first deposited on a nickel foam substrate using a direct current method. Then, a nickel-cobalt-manganese ternary alloy with a nanosheet morphology was deposited on the nanocones using a cyclic voltammetry method with different cycles and sweep rates. The results show that the sample synthesized in 3 cycles with a sweep rate of 10 mV s-1 exhibits the best electrocatalytic activity and requires -81, -121, and -214 mV overpotentials to reach 10, 20 and 100 mA cm-2 current densities, respectively. Electrochemical impedance spectroscopy studies also improved the HER performance with the lowest charge transfer resistance among all of the synthesized electrodes. This study introduces an effective and facile method for the fabrication of highly active and stable electrocatalysts.

Dopamine-modified cobalt spinel nanoparticles as an active catalyst for the acidic oxygen evolution reaction.

The development of efficient non-noble metal electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions remains a critical challenge. Herein, we report a N-doped carbonaceous component-engineered Co3O4 (NCEC) catalyst synthesized via the sol-gel method. Dopamine hydrochloride (DA)-derived nitrogen-doped carbonaceous components were found to boost the OER performance of Co3O4. The optimized catalyst can reach an overpotential as low as 330 mV in 1 M H2SO4 at a current density of 10 mA cm-2 and maintains a good long-term stability of 60 hours. In particular, we found that the thermodynamic overpotential was inversely proportional to the content of oxidized N and pyridinic N, whereas it was directly proportional to the pyrrolic-N content. Our experiments and density functional theory (DFT) calculations confirm that the optimized catalyst exhibits enhanced charge transfer and the oxidized N species on Co3O4 is responsible for the high catalytic activity. Our study suggests that the performance of NCEC in acidic media can be further optimized by enhancing the content of oxidized N species.

Silver-M-Phathalocyanine (M= Co,Fe,Cu) Electrocatalysts for Oxygen Reduction Reaction in H2/O2 Anion Exchange Membrane Fuel Cells

In the transition from fossil fuels to clean energy sources, H2 plays a key role due to its high energy density, and direct conversion to electricity in fuel cells (FCs). FCs are devices that allow the clean conversion of chemical energy into electrical energy. In H2/O2 fuel cell the hydrogen oxidation reaction (HOR) occurs at the anodic electrode, while at the cathodic side oxygen is reduced into water (ORR). The electrodes are separated by a conductive membrane, that could exchange protons (Proton Exchange Membrane, PEM) or anions (Anion Exchange Membrane, AEM) to maintain the electro-neutrality of the system. AEMFCs are an attractive alternative to PEMFCs, thanks to the alkaline noncorrosive enviroment that allows the use of cheaper structural materials such as non-noble metal electrocatalysts. This work is centred on the study of silver (Ag) nanostructured electrocatalysts in ORR for the realization of a platinum-free AEMFCs. Ag nanoparticles promote, in alkaline media, a 4e- pathway of the ORR, optimizing the conversion of oxygen into water at the expense of hydrogen peroxide.1 However, the activity of Ag is limited by the strong hydroxide anion (OH-) binding energy, which reduces the free active sites destined to oxygen adsorption.1 To overcome this, Ag electrocatalysts were modified with metal-phthalocyanines (M-Pc M=Co, Fe, Cu) and supported on Ketjen-black carbon and on Ceria/Ketjen black (CeO2/C) supports. The synergistic effect between M-Pc and Ag NPs optimizes the OH- binding energy enhancing the ORR performances.2,3 The employment of ceria, thanks to its high oxophylicity, improves the transfer of OH- to the metal surface.4,5 The dispersion and size of nanoparticles (5-15 nm) was controlled through the Turkevich synthesis method, in order to maximize the interaction between Ag and Me-Pc. Physical characterization has been realized by High Resolution Trasmission Electron Microscopy (HR-TEM), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) while electrochemical behaviour has been explored in half cells and in complete AEMFCs. References Erikson, H., Sarapuu, A., & Tammeveski, K. (2019). Oxygen reduction reaction on silver catalysts in alkaline media: a minireview. ChemElectroChem, 6(1), 73-86.. Miller, H. A., Bevilacqua, M., Filippi, J., Lavacchi, A., Marchionni, A., Marelli, M., ... & Vizza, F. (2013). Nanostructured Fe–Ag electrocatalysts for the oxygen reduction reaction in alkaline media. Journal of Materials Chemistry A, 1(42), 13337-13347. Miller, H. A., Bellini, M., Oberhauser, W., Deng, X., Chen, H., He, Q., ... & Vizza, F. (2016). Heat treated carbon supported iron (ii) phthalocyanine oxygen reduction catalysts: elucidation of the structure–activity relationship using X-ray absorption spectroscopy. Physical Chemistry Chemical Physics, 18(48), 33142-33151. Miller, H. A., Bellini, M., Dekel, D. R., & Vizza, F. (2022). Recent developments in Pd-CeO2 nano-composite electrocatalysts for anodic reactions in anion exchange membrane fuel cells. Electrochemistry Communications, 135, 107219. Bellini, M., Pagliaro, M. V., Marchionni, A., Filippi, J., Miller, H. A., Bevilacqua, M., ... & Vizza, F. (2021). Hydrogen and chemicals from alcohols through electrochemical reforming by Pd-CeO2/C electrocatalyst. Inorganica Chimica Acta, 518, 120245. Figure 1

FeN4 Active Sites Electronically Coupled with PtFe Alloys for Ultralow Pt Loading Hybrid Electrocatalysts in Proton Exchange Membrane Fuel Cells.

The exorbitant cost of Pt-based electrocatalysts and the poor durability of non-noble metal electrocatalysts for proton exchange membrane fuel cells limited their practical application. Here, FeN4 active sites electronically coupled with PtFe alloys (PtFe-FeNC) were successfully prepared by a vapor deposition strategy as an ultralow Pt loading (0.64 wt %) hybrid electrocatalyst. The FeN4 sites on the FeNC matrix are able to effectively anchor the PtFe alloys, thus inhibiting their aggregation during long-life cycling. These PtFe alloys, in turn, can efficiently restrain the leaching of the FeN4 sites from the FeNC matrix. Thus, the PtFe-FeNC demonstrated an improved Pt mass activity of 2.33 A mgPt-1 at 0.9 V toward oxygen reduction reaction, which is 12.9 times higher than that of commercial Pt/C (0.18 A mgPt-1). It demonstrated great stability, with the Pt mass activity decreasing by only 9.4% after 70,000 cycles. Importantly, the fuel cell with an ultralow Pt loading in the cathode (0.012 mgPt cm-2) displays a high Pt mass activity of 1.75 A mgPt-1 at 0.9 ViR-free, which is significantly better than commercial MEA (0.25 A mgPt-1). Interestingly, PtFe-FeNC catalysts possess enhanced durability, exhibiting a 12.5% decrease in peak power density compared to the 51.7% decrease of FeNC.

Amorphous Ni-Fe-Co-P-B nanosheets as efficient electrocatalyst for oxygen evolution reaction

Non-noble metal electrocatalysts with hierarchically structural design and heteroatom-doped is highly urgent for high-efficiency, low-cost electrochemical water splitting systems. Herein, this paper uses a simple and low-cost method to synthesize amorphous carbon-based Ni-Fe-Co-B-P composite material as efficient OER catalyst. Specifically, the catalytic performance can be enhanced through processes such as etching-recombination-reduction. First, we use ZIF-67 as the precursor to provide Co source and carbon source. Fe and Ni are creatively incorporated into the Co3O4 lattice as auxiliary metal atoms. Then, the above three metal oxides were simultaneously reduction with NaH2PO2 and NaBH4. Although this is the first time that MOF-based materials have been treated with P and B, the resulting samples are chemically stable. The obtained amorphous carbon-based material Ni-Fe-Co-B-P benefits from the advantages of its structure and composition, showing that the electron density is rearranged around the center of the catalytic metal atom and the energy barrier formed by the intermediate is reduced by weakening the metal-metal bond, thereby exhibiting excellent electrochemical performance. The overpotential to afford the current density of 10 mA cm-2 (268 mV) and the small Tafel slope (51.83 mV dec-1) show a predatorily competitive advantage compared with commercially available RuO2 (284 mV and 69.34 mV dec-1 respectively).

Porous W/N/C nanoframework: A trifunctionally effective cathodic electrocatalyst for rechargeable Zn-Air/iodide hybrid battery

Different from the conventional Zinc-Air batteries which only involves oxygen reduction and evolution (ORR/OER) in the cathode, the cathode of rechargeable zinc–air/iodide hybrid batteries (ZAIHBs), with the addition of I− species, involves I− electrooxidation (IOR) during charging and oxygen/iodate reduction (ORR and IDR) during discharging. This work reports the synthesis of a hierarchically porous tungsten-based nitrogen-doped carbon framework (W/N/C) with abundant WNx active sites and numerous ultrafine WN nanoclusters and explores their application as a trifunctional IOR/ORR/IDR electrocatalyst for ZAIHBs. The formation mechanism of ZIF-8-derived W/N/C framework as well as its structural and compositional features were investigated. The catalyst demonstrates high trifunctional catalytic activity and robust durability towards IOR/ORR/IDR in alkaline condition, owing to the uniform copresence of the numerous sub-nanometer-sized WN nanoclusters and the abundant single atom WNx sites in the hierarchically structured carbon framework. When applied in homemade ZAIHBs, it revealed a high peak energy density (141.9 mW cm−2) and remarkable cycling stability (65 h), outperforming the commercial Pt/C catalysts. This work demonstrates the multi-functional electrocatalytic activity of tungsten-based non-noble metal electrocatalyst for high-performance ZAIHBs.

Highly Efficient Cobalt Sulfide Heterostructures Fabricated on Nickel Foam Electrodes for Oxygen Evolution Reaction in Alkaline Water Electrolysis Cells

Non-noble metal electrocatalysts for the oxygen evolution reaction (OER) have recently gained particular attention. In the present work, a facile one-step electrodeposition method is applied in situ to synthesize cobalt sulfide nanostructures on nickel foam (NF) electrodes. For the first time, a systematic study is carried out on the impact of the Co/S molar ratio on the structural, morphological, and electrochemical characteristics of Ni-based OER electrodes by employing Co(NO3)2·6 H2O and CH4N2S as Co and S precursors, respectively. The optimum performance was obtained for an equimolar Co:S ratio (1:1), whereas sulfur-rich or Co-rich electrodes resulted in an inferior behavior. In particular, the CoxSy@NF electrode with Co/S (1:1) exhibited the lowest overpotential value at 10 mA cm−2 (0.28 V) and a Tafel slope of 95 mV dec−1, offering, in addition, a high double-layer capacitance (CDL) of 10.7 mF cm−2. Electrochemical impedance spectroscopy (EIS) measurements confirmed the crucial effect of the Co/S ratio on the charge-transfer reaction rate, which is maximized for a Co:S molar ratio of 1:1. Moreover, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF) were conducted to gain insights into the impact of the Co/S ratio on the structural and morphological characteristics of the electrodes. Notably, the CoxSy@NF electrocatalyst with an equimolar Co:S ratio presented a 3D flower-like nanosheet morphology, offering an increased electrochemically active surface area (ESCA) and improved OER kinetics.

Interface regulation of Zr-MOF/Ni2P@nickel foam as high-efficient electrocatalyst for pH-universal hydrogen evolution reaction

Currently, the development of economical and effective non-noble metal electrocatalysts is vital for advancing hydrogen evolution reaction (HER) and enabling its widespread applications. The customizable pore structure and enormous surface area of metal–organic frameworks (MOFs) have made them to become promising non-noble metal electrocatalysts for HER. However, MOFs have some challenges, including low conductivity and instability, which can result in them having high overpotentials and slow reaction kinetics in electrocatalytic processes. In this work, we present an innovative approach for synthesizing cost-effective and high-efficient Zr-MOF-derived pH-universal electrocatalysts for HER. It entails creating the interfaces of the electrocatalysts with suitable proportions of phosphide nanostructures. Zr-MOF/Ni2P@nickel foam (NF) electrodes with interface regulated by Ni2P nanostructures were successfully developed for high-efficient pH-universal HER electrocatalysts. The presence of Ni2P nanostructures with abundant active sites at the Zr-MOFs@NF interfaces boosted the electronic conductivity and local charge density of the hybrid electrocatalysts. This helped to improve their reaction kinetics and electrocatalytic activity. By optimizing the Ni2P amount, Zr-MOF/Ni2P@NF demonstrated impressive stability and superior HER activities, with a low overpotential of 149 mV (acidic electrolytes) and 143 mV (alkaline electrolytes) at 10 mA cm−2. The proven strategy in this work can be expanded to many types of MOF-based materials for wider practical applications.

Collaborative coupling catalytic interface enabling efficient hydrogen evolution in universal-pH electrolytes and seawater

Developing particularly effective and synergistic non-noble metal electrocatalysts for complex chemical processes remains an enormous challenge. Herein, the collaborative catalytic interface among rare earth compounds, bimetallic carbide, and N-doped carbon is demonstrated to accelerate the hydrogen evolution process in acid-base electrolytes and seawater. Therefore, the HER performance of the resultant electrocatalyst in both 1.0 M KOH and 0.5 M H2SO4 with the overpotentials of 70 and 79 mV, to achieve the current density of 10 mA cm−2. In addition, they also show excellent performance of HER in natural seawater and have good characteristics in catalytic activity and stability, which is reflected in the slight decrease of activity after the 5000 cyclic voltammetry (CV) cycle and almost no attenuation after electrolysis for 10 h. This work will pave a new way for collaborative coupling interface catalysis strategy to boost electrocatalytic hydrogen production in acidic, alkaline, and seawater.