Freestanding Surface Disordered NiCu Solid Solution as Ultrastable High Current Density Hydrogen Evolution Reaction Electrode

Design and fabrication of intermetallic NiCo electrocatalysts for the alkaline HER

The design and fabrication of highly efficient electrocatalysts are crucial for reducing energy consumption, improving hydrogen production rates, and prolonging the service life of alkaline electrolyzers. In this study, intermetallic L10-NiCo electrocatalysts were designed using DFT calculations and fabricated through a one-step solid-state reaction method. The DFT calculations indicated that L10-NiCo presented a lower H adsorption Gibbs free energy and a moderate H2O dissociation barrier compared to the commonly used Ni catalyst and disordered NiCo alloy. Increasing the solid-state reaction temperature facilitated the formation of intermetallic L10-NiCo. Electrocatalytic tests for the alkaline HER demonstrated that the ECSA of L10-NiCo nanoparticles increased to 2.3 times, the overpotential decreased by 19%, the electrocatalytic activity increased to 1.5 times, and the stability improved to 2.2 times compared to those of the Ni nanoparticles. This research provides insights into the design and fabrication of highly efficient catalytic electrodes for alkaline electrolyzers.

Spark plasma sintered catalytic nickel-copper alloy and carbon nanotube electrodes for the hydrogen evolution reaction

We report the proof-of-concept of spark plasma sintered (SPS) consolidated mesoporous composite catalytic electrodes based on nickel-copper alloys and carbon nanotubes for the electrocatalytic hydrogen evolution reaction (HER) in alkaline media. The optimized electrode (203 m2 g-1, 5 wt% Ni75Cu25) operated at -0.1 A cm-2 (current of -0.15 A) for 24 h with a stable overpotential of about 0.3 V. This newly described freestanding SPS approach allows the rational control of specific surface area, metal loading, and electrocatalytic performance, thus opening a new route to catalytic electrodes with controllable physical and catalytic properties.

Duplex Interpenetrating-Phase FeNiZn and FeNi3 Heterostructure with Low-Gibbs Free Energy Interface Coupling for Highly Efficient Overall Water Splitting

The sluggish kinetics of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) generate the large overpotential in water electrolysis and thus high-cost hydrogen production. Here, multidimensional nanoporous interpenetrating-phase FeNiZn alloy and FeNi3 intermetallic heterostructure is in situ constructed on NiFe foam (FeNiZn/FeNi3@NiFe) by dealloying protocol. Coupling with the eminent synergism among specific constituents and the highly efficient mass transport from integrated porous backbone, FeNiZn/FeNi3@NiFe depicts exceptional bifunctional activities for water splitting with extremely low overpotentials toward OER and HER (η1000 = 367/245 mV) as well as the robust durability during the 400 h testing in alkaline solution. The as-built water electrolyzer with FeNiZn/FeNi3@NiFe as both anode and cathode exhibits record-high performances for sustainable hydrogen output in terms of much lower cell voltage of 1.759 and 1.919 V to deliver the current density of 500 and 1000 mA cm-2 as well long working lives. Density functional theory calculations disclose that the interface interaction between FeNiZn alloy and FeNi3 intermetallic generates the modulated electron structure state and optimized intermediate chemisorption, thus diminishing the energy barriers for hydrogen production in water splitting. With the merits of fine performances, scalable fabrication, and low cost, FeNiZn/FeNi3@NiFe holds prospective application potential as the bifunctional electrocatalyst for water splitting.

Solar-driven methanogenesis with ultrahigh selectivity by turning down H2 production at biotic-abiotic interface

Integration of methanogens with semiconductors is an effective approach to sustainable solar-driven methanogenesis. However, the H₂ production rate by semiconductors largely exceeds that of methanogen metabolism, resulting in abundant H₂ as side product. Here, we report that binary metallic active sites (namely, NiCu alloys) are incorporated into the interface between CdS semiconductors and Methanosarcina barkeri. The self-assembled Methanosarcina barkeri-NiCu@CdS exhibits nearly 100% CH₄ selectivity with a quantum yield of 12.41 ± 0.16% under light illumination, which not only exceeds the reported biotic-abiotic hybrid systems but also is superior to most photocatalytic systems. Further investigation reveal that the Ni-Cu-Cu hollow sites in NiCu alloys can directly supply hydrogen atoms and electrons through photocatalysis to the Methanosarcina barkeri for methanogenesis via both extracellular and intracellular hydrogen cycles, effectively turning down the H₂ production. This work provides important insights into the biotic-abiotic hybrid interface, and offers an avenue for engineering the methanogenesis process.