Plasma Transforming Ni(OH)2 Nanosheets into Porous Nickel Nitride Sheets for Alkaline Hydrogen Evolution

Modulating adsorption energy on nickel nitride-supported ruthenium nanoparticles through in-situ electrochemical activation for urea-assisted alkaline hydrogen production

The rational design of electrocatalysts with exceptional performance and durability for hydrogen production in alkaline medium is a formidable challenge. In this study, we have developed in-situ activated ruthenium nanoparticles dispersed on Ni3N nanosheets, forming a bifunctional electrocatalyst for hydrogen evolution and urea oxidation. The results of experimental analysis and theoretical calculations reveal that the enhanced hydrogen evolution reaction (HER) performance of O-Ru-Ni3N stems primarily from the optimized hydrogen adsorption and hydroxyl adsorption on Ru sites. The O-Ru-Ni3N on nickel foam (NF) electrode exhibits excellent HER performance, requiring only 29 mV to reach 10 mA cm-2 in an alkaline medium. Notably, when this O-Ru-Ni3N/NF catalyst is employed for both HER and urea oxidation reaction (UOR) to create an integrated H2 production system, a current density of 50 mA cm-2 can be generated at the cell voltage of 1.41 V. This report introduces an energy-efficient catalyst for hydrogen production and proposes a viable strategy for anodic activation in energy chemistry.

Surface plasmon-enhanced photo-driven CO2 hydrogenation by hydroxy-terminated nickel nitride nanosheets

The majority of visible light-active plasmonic catalysts are often limited to Au, Ag, Cu, Al, etc., which have considerations in terms of costs, accessibility, and instability. Here, we show hydroxy-terminated nickel nitride (Ni₃N) nanosheets as an alternative to these metals. The Ni₃N nanosheets catalyze CO₂ hydrogenation with a high CO production rate (1212 mmol g^-1 h^-1) and selectivity (99%) using visible light. Reaction rate shows super-linear power law dependence on the light intensity, while quantum efficiencies increase with an increase in light intensity and reaction temperature. The transient absorption experiments reveal that the hydroxyl groups increase the number of hot electrons available for photocatalysis. The in situ diffuse reflectance infrared Fourier transform spectroscopy shows that the CO₂ hydrogenation proceeds via the direct dissociation pathway. The excellent photocatalytic performance of these Ni₃N nanosheets (without co-catalysts or sacrificial agents) is suggestive of the use of metal nitrides instead of conventional plasmonic metal nanoparticles.

In situ synthesis of two-dimensional graphene-like nickel-molybdenum nitride as efficient electrocatalyst towards water-splitting under large-current density

Transition metal nitride (TMNs) electrocatalysts have attracted tremendous attentions for their unique electron structure, high activity, and excellent stability. Herein, a two-dimensional (2D) graphene-like structured nickel-molybdenum nitride (Ni-MoN) on nickel foam (NF), is prepared via facile hydrothermal and following nitridation process. The as-prepared Ni-MoN-450 (pyrolysis at 450 °C) displays good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances in alkaline media. Only 22 mV and 117 mV are needed to achieve current densities of 10 mA cm^-2 and 500 mA cm^-2 in 1.0 M KOH, respectively, toward HER. The assembled two-electrode system, with the synthesized Ni-MoN-450 as the anode and cathode, exhibits good performance to achieve 1000 mA cm^-2 in 1.0 M KOH + 25 °C and 6.0 M KOH + 80 °C. Moreover, it also presents long-term stability under large-current density, which verified its robust property.

Kirkendall effect Strengthened-Superhydrophilic/superaerophobic Co-Ni3N/NF heterostructure as electrode catalyst for High-current hydrogen production

The development of efficient electrocatalysts for large-scale water electrolysis is crucial and challenging. Research efforts towards interface engineering and electronic structure modulation can be leveraged to enhance the electrochemical performance of the developed catalysts. In this work, a surface-engineered Co-Ni₃N/NF heterostructure electrode was prepared based on Kirkendall effect for high-current water electrolysis. In the experiments, the textural feature and intrinsic activity of the Co-Ni₃N/NF heterostructure were tuned through cobalt-doping and the creation of structural defects. As a result, the increased surface energy endowed Co-Ni₃N/NF heterostructure with superhydrophilic and superaerophobic properties. Meanwhile, the contact area of the gas-liquid-solid three phases was optimized. With a large underwater bubble contact angle (CA) of 169°, the electrolyte solution can infiltrate the Co-Ni₃N/NF electrode within 150 ms. Sequentially, the generated gas bubbles were able to detach at high frequency, which ensured the rapid mass exchange. The performance tests showed that the optimal Co-Ni₃N/NF electrode sample reached current densities of 100 mA cm^-2 and 500 mA cm^-2 at the overpotentials of 98 mV and 123 mV, respectively. Benefiting from the reduction of hydrogen embrittlement, the HER performance of the prepared Co-Ni₃N/NF electrode sample decreased slightly after 100 h durability test, but the overall structure remained well. Those results allowed us to conclude that the prepared Co-Ni₃N/NF electrocatalyst holds the promises for large-scale water electrolysis in industries. More specifically, this work provided a new perspective that the efficiency of electrocatalysts for large-scale water electrolysis can be enhanced by constructing a heterostructure with good wettability and gas repellency.

Facet Control of Nickel Nitride Nano-Framework for Efficient Hydrogen Evolution Electrocatalysis via Auxiliary Cooling Assisted Plasma Engineering

The precise facet modulation of transition metal nitrides (TMNs) has been regarded as an essential issue in boosting electrocatalytic H₂ production. Compared to thermal nitridation, the plasma technique serves as a favorable alternative to directly achieve TMNs, but the apparent surface heating effect during plasma treatment inevitably causes the thermally stabilized nitride formation, resulting in the deterioration of the highly reactive facet. To optimize the hydrogen evolution reaction (HER) behavior, an auxiliary cooling assisted plasma system to selectively expose Ni₃ N (2-10) with favorable activity by controlling surface heating during plasma nitridation is designed. The resultant nickel nitride (cp-Ni₃ N) nano-framework delivers exceptional catalytic performance, evidenced by its low overpotential of 58 and 188 mV at the current density of 10 and 100 mA cm^-2 for HER, in stark comparison with that of normal plasma and thermally fabricated Ni₃ N. Operando plasma diagnostics along with numerical simulation further confirm the effect of surface heating on typical plasma parameters as well as the Ni₃ N nanostructure, indicating the key factor responsible for the high-performance nitride electrocatalyst.

Transition metal nitrides for electrochemical energy applications

This review comprehensively summarizes the progress on the structural and electronic modulation of transition metal nitrides for electrochemical energy applications.

Ni(OH)2–Ag hybrid nanosheet array with ultralow Ag loading as a highly efficient and stable electrocatalyst for hydrogen evolution reaction

0D Ag nanoparticles were successfully loaded onto 2D Ni(OH)₂ nanosheets on 3D nickel foam by a one-step hydrothermal method for enhancing the electrocatalytic ability.

Plasma modified BiOCl/sulfonated graphene microspheres as efficient photo-compensated electrocatalysts for the oxygen evolution reaction

Plasma regulation of oxygen vacancies in BiOCl/sulfonated graphene composites enables light energy compensation for the electrocatalytic OER process.