Self-supported 3D porous N-Doped nickel selenide electrode for hydrogen evolution reaction over a wide range of pH

Synergistic design of hierarchical and heterostructural P-NiMoO4@Net-like Ni2P for enhanced hydrogen evolution electrocatalysis

Hierarchical structure design and heterostructure engineering are effective strategies for enhancing hydrogen evolution reaction (HER) performance, yet their synergistic integration remains underexplored. In this work, a novel hierarchical P-NiMoO4@Net-like Ni2P heterostructure HER electrocatalyst was prepared via a two-step hydrothermal method followed by low-temperature phosphorization. The three-dimensional net like Ni2P was closely integrated with one-dimensional phosphorus-doped NiMoO4 micro/nanorod arrays, enabling hierarchical structural assembly and the formation of synergistic heterointerfaces. The hierarchical structure significantly increased active site exposure, with a double-layer capacitance of 254.4 mF cm-2, more than five times that of single-component Ni2P (48.4 mF cm-2). Density functional theory calculations revealed that the heterostructure lowered the d-band center of active Ni3 sites and optimized the hydrogen adsorption energy, thereby enhancing HER activity. The P-NiMoO4@Net-like Ni2P catalyst exhibited an alkaline HER overpotential of 49 mV at a current density of 10 mA cm-2. It also maintained stable operation for 100 h at 10mA cm-2 and 120 h at 100mA cm-2. This study demonstrates the potential of integrating hierarchical and heterostructural strategies, providing a reference for advanced nanostructured catalyst development.

Electrodeposition and Optimisation of Amorphous NixSy Catalyst for Hydrogen Evolution Reaction in Alkaline Environment

Anion exchange membrane (AEM) water electrolysers have shown their potential in green hydrogen production. One of the crucial tasks is to discover novel cost-effective and sustainable electrocatalyst materials. In this study, a low-cost Ni-S-based catalyst for hydrogen evolution reaction was prepared via a simple electrodeposition process from a modified Watts bath recipe. Physical characterisation methods suggest this deposit film to be amorphous. Optimisation of the electrodeposition parameters of the NixSy catalyst was carried out using a rotating disk electrode setup. The optimised catalyst exhibited excellent catalytical performance in 1 M KOH on a microelectrode, with overpotentials of 41 mV, 111 mV and 202 mV at 10, 100 and 1000 mA cm-2 with Tafel slope of 67.9 mV dec-1 recorded at 333 K. Long-term testing of the catalyst demonstrated steady performance over a 24 h period on microelectrode at 100 mA cm-2 with only 71 mV and 37 mV overpotential increase at 293 K and 333 K respectively. Full cell testing with the optimised NixSy as cathode and NiFe(OH)2 as anode showed 1.88 V after 1 h electrolysis at 500 mA cm-2 in 1 M KOH under 333 K with FAA-3-30 membrane.

Electronic structure engineering on NiSe2 micro-octahedra via nitrogen doping enabling long cycle life magnesium ion batteries

Multivalent ion batteries have attracted great attention because of their abundant reserves, low cost and high safety. Among them, magnesium ion batteries (MIBs) have been regarded as a promising alternative for large-scale energy storage device owing to its high volumetric capacities and unfavorable dendrite formation. However, the strong interaction between Mg²⁺ and electrolyte as well as cathode material results in very slow insertion and diffusion kinetics. Therefore, it is highly necessary to develop high-performance cathode materials compatible with electrolyte for MIBs. Herein, the electronic structure of NiSe₂ micro-octahedra was modulated by nitrogen doping (N-NiSe₂) through hydrothermal method followed by a pyrolysis process and this N-NiSe₂ micro-octahedra was used as cathode materials for MIBs. It is worth noting that N-NiSe₂ micro-octahedra shows more redox active sites and faster Mg²⁺ diffusion kinetics compared with NiSe₂ micro-octahedra without nitrogen doping. Moreover, the density functional theory (DFT) calculations indicated that the doping of nitrogen could improve the conductivity of active materials on the one hand, facilitating Mg²⁺ ion diffusion kinetics, and on the other hand, nitrogen dopant sites could provide more Mg²⁺ adsorption sites. As a result, the N-NiSe₂ micro-octahedra cathode exhibits a high reversible discharge capacity of 169 mAh g^-1 at the current density of 50 mA g^-1, and a good cycling stability over 500 cycles with a maintained discharge capacity of 158.5 mAh g^-1. This work provides a new idea to improve the electrochemical performance of cathode materials for MIBs by the introduction of heteroatom dopant.

Cobalt, Ferrum Co-Doped Ni3Se4 Nano-Flake Array: An Efficient Electrocatalyst for the Alkaline Hydrogen Evolution and Overall Water Splitting

Herein, Co, Fe co-doped Ni3Se4 nano-flake array (Ni0.62Co0.35Fe0.03)3Se4) was prepared on conductive carbon cloth by a two-step hydrothermal method. XRD and EDX analysis show that the nanosheets are monoclinic Ni3Se4, and Co, and Fe were doped into the lattice of Ni3Se4. Electrochemical tests showed that Co, Fe co-doping can effectively improve the hydrogen evolution activity of Ni3Se4 in acidic and alkaline environment. When the current density of (Ni0.62Co0.35Fe0.03)3Se4/CC is 10 mA/cm2 in 1 M KOH solution, the overpotentials of hydrogen evolution and oxygen evolution are 87 mV and 53.9 mV, respectively, and the Tafel slopes are 122.6 and 262 mV/dec. The electrochemical active area test (ECSA) and the polarization curve test further show that (Ni0.62Co0.35Fe0.03)3Se4/CC has a larger electrochemical active area (34.8 mF/cm2), lower electrolytic potential (0.9 V at 10 mA/cm2) and better stability. Therefore, the novel bifunctional catalyst synthesized by a simple method is a promising candidate for large-scale industrial water electrolysis.

Agaric-like cobalt diselenide supported by carbon nanofiber as an efficient catalyst for hydrogen evolution reaction

We synthesized herein a novel 3D cathode constructed by growing cobalt diselenide in situ on the surface of carbon nanofiber for hydrogen evolution reaction. The cobalt diselenides with two typical morphologies (agaric-like and nanorod-like) were synthesized by precisely controlling reaction time and temperature in the same system. They show excellent electrocatalytic performance for hydrogen evolution reactions. Especially, the agaric-like diselenide cobalt electrode has the low overpotential (187 and 199 mV) to obtain the current density of 50 and 100 mA cm^-2 with a small Tafel slope of 37 mV dec^-1 in acidic medium. The excellent catalytic performance of the agaric-like cobalt diselenide can be attributed to its large specific surface area and fast electron transfer rate. More importantly, the agaric-like cobalt diselenide supported carbon nanofiber electrode has excellent long-term stability in electrolyte. The outstanding electrocatalytic performance and stability of agaric-like cobalt diselenide supported carbon nanofiber indicate that it is a promising electrocatalyst for hydrogen evolution reactions.

Emergence of Ni-Based Chalcogenides (S and Se) for Clean Energy Conversion and Storage

Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco-friendly nature, and low cost. The present review compiles recent progress in the area of nickel-(S and Se)-based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano-structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro-active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future development of these materials for energy-oriented devices with high performance.

Towards the Hydrogen Economy—A Review of the Parameters That Influence the Efficiency of Alkaline Water Electrolyzers

Environmental issues make the quest for better and cleaner energy sources a priority. Worldwide, researchers and companies are continuously working on this matter, taking one of two approaches: either finding new energy sources or improving the efficiency of existing ones. Hydrogen is a well-known energy carrier due to its high energy content, but a somewhat elusive one for being a gas with low molecular weight. This review examines the current electrolysis processes for obtaining hydrogen, with an emphasis on alkaline water electrolysis. This process is far from being new, but research shows that there is still plenty of room for improvement. The efficiency of an electrolyzer mainly relates to the overpotential and resistances in the cell. This work shows that the path to better electrolyzer efficiency is through the optimization of the cell components and operating conditions. Following a brief introduction to the thermodynamics and kinetics of water electrolysis, the most recent developments on several parameters (e.g., electrocatalysts, electrolyte composition, separator, interelectrode distance) are highlighted.

Structure-controlled tungsten carbide nanoplates for enhanced hydrogen evolution reaction

Developing a low-cost and durable non-noble metal eletrocatalyst for hydrogen evolution reaction (HER) is critical in efficient hydrogen production. Herein, tungsten carbide nanoplates (WC NPs) with typical mesoporous structure were prepared by a controlled hydrothermal reaction followed by a gas-solid carburization process. The crystal phases, microstructure and chemical components of the nanoplates were characterized, and their electrochemical properties were measured. The results show that the as-prepared WC NPs expose active sites upmost, and exhibit enhanced conductivity and superior HER performance in acid solution in terms of a small η 10 (overpotential to obtain a current density of 10 mA cm−2) of 120 mV, a Tafel slope of 58 mV dec−1 and outstanding long-term cycling stability. These indicate that the HER properties of WC NPs are dramatically enhanced compared to that of all phase pure WC materials reported in recent years. This enhancement can be attributed to their unique structural and electronic properties, which can be exploited to improve the electrochemical properties of traditional non-noble metal material.

Computational Screening toward Hydrogen Evolution Reaction by the Introduction of Point Defects at the Edges of Group IVA Monochalcogenides: A First-Principles Study

Exploring materials with high hydrogen evolution reaction (HER) performance is of importance for the development of clean hydrogen energy, and the defects on the surfaces of catalysts are essential. In this work, we evaluate the HER performance among group IVA monochalcogenides MXs (M = Ge/Sn, X = S/Se) with M/X point defects on the edges. Compared with basal planes and bare edges, the GeS edge with Ge vacancy (ΔG_H* = 0.016 eV), GeSe edge with Se vacancy (ΔG_H* = 0.073 eV), and SnSe edge with Sn vacancy (ΔG_H* = -0.037 eV) hold the best HER performances, which are comparable to or even better than the value for Pt (-0.07 eV). Furthermore, the relationships between ΔG_H* and p-band centers of considered models are summarized. The stability of proposed electrocatalysts are analyzed by vacancy-formation energy and strain engineering. In summary, the HER performance of MXs is greatly improved by introduction of point defects at the edges, which is promising for their use as electrocatalysts for the conversion and storage of energy in the future.

Recent progress in transition metal selenide electrocatalysts for water splitting

The urgent demand of scalable hydrogen production has motivated substantial research on low cost, efficient and robust catalysts for water electrolysis. In order to replace noble metals and their derivatives, transition metal (Fe, Co, Ni, Mo, Cu, etc.) selenides have demonstrated promising catalysis on both hydrogen and oxygen evolutions. Very recently, a number of reports have presented a variety of approaches to enhance their electrocatalytic activity. This review summarizes the most recent progress in transition metal selenide electrocatalysts for HER, OER, and overall water splitting. The merits and limitations of metal selenides are also discussed in the aspects of structure and composition. Moreover, we highlight new strategies and future challenges for design and synthesis of high performance electrocatalysts.

Amorphous Ni–Fe–Se hollow nanospheres electrodeposited on nickel foam as a highly active and bifunctional catalyst for alkaline water splitting

The electrodeposition of amorphous Ni–Fe–Se hollow nanospheres as a highly efficient bifunctional catalyst for the sustainable production of hydrogen.