Amorphous Nickel-Based Thin Film As a Janus Electrocatalyst for Water Splitting

Hydrogen generated by water splitting provides a renewable energy source, but development of materials with efficient electrocatalytic water splitting capability is challenging. Thin-film electrocatalytic material (H₂–NiCat) with robust water reduction properties, which can be readily prepared by a reduction-induced electrodeposition method from nickel salts in a borate-buffered electrolyte (pH 9.2), is reported. The material consists of nanoparticles with nickel oxide or hydroxide species located at the surface and metallic nickel in the bulk. The catalyst mediates H₂ evolution in a near-neutral aqueous buffer at low overpotential. The catalyst requires a subsequent oxidative pretreatment in order to attain a well-defined hydrogen evolution reaction (HER) activity, and the 1.5 h anodized catalyst film exhibits a HER current density of about 1.50 mA cm^–2 at 0.452 V overpotential over a period of 24 h with no observable corrosion. In addition, it can be converted by anodic equilibration into an amorphous Ni-based oxide film (O₂–NiCat) to catalyze O₂ evolution, and the switch between the two catalytic forms is fully reversible. The robust, bifunctional, switchable, and noble-metal-free catalytic material has immense potential in artificial solar water-splitting devices

High-Efficiency Electrochemical Hydrogen Evolution Based on Surface Autocatalytic Effect of Ultrathin 3C-SiC Nanocrystals

Good understanding of the reaction mechanism in the electrochemical reduction of water to hydrogen is crucial to renewable energy technologies. Although previous studies have revealed that the surface properties of materials affect the catalytic reactivity, the effects of a catalytic surface on the hydrogen evolution reaction (HER) on the molecular level are still not well understood. Contrary to general belief, water molecules do not adsorb onto the surfaces of 3C-SiC nanocrystals (NCs), but rather spontaneously dissociate via a surface autocatalytic process forming a complex consisting of −H and −OH fragments. In this study, we show that ultrathin 3C-SiC NCs possess superior electrocatalytic activity in the HER. This arises from the large reduction in the activation barrier on the NC surface enabling efficient dissociation of H₂O molecules. Furthermore, the ultrathin 3C-SiC NCs show enhanced HER activity in photoelectrochemical cells and are very promising to the water splitting based on the synergistic electrocatalytic and photoelectrochemical actions. This study provides a molecular-level understanding of the HER mechanism and reveals that NCs with surface autocatalytic effects can be used to split water with high efficiency thereby enabling renewable and economical production of hydrogen