Tuning the coupling interface of a heterostructured catalyst is an effective approach to achieve abundant surface catalytic active sites and strong electronic interactions among active materials for improving electrocatalytic water splitting performance. Herein, we report a novel heterogeneous catalyst comprising Ni₃S₂ nanoparticles embedded in ultrathin NiV-layered double hydroxide nanosheet arrays supported on nickel foam, denoted as Ni₃S₂@NiV-LDH/NF. We demonstrate that the active edge-state length and the surface chemical state of such NiV-LDH-based heterostructures are well modulated by tailoring the coupling interfaces, resulting in the exposure of more catalytic reaction sites and enhancement of the electronic interactions between NiV-LDH and Ni₃S₂, thus greatly promoting the water dissociation kinetics. As expected, the optimized Ni₃S₂@NiV-LDH/NF heterostructures exhibit outstanding electrocatalytic activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with an extremely low overpotential of 126 mV and 190 mV to deliver 10 mA cm⁻² for the HER and OER without iR compensation in alkaline media, respectively. More importantly, Ni₃S₂@NiV-LDH/NF simultaneously functioned as both the anode and cathode for water splitting to yield a current density of 10 mA cm⁻² at a cell voltage of only 1.53 V with an outstanding durability for 160 h. This work provides a new insight into the regulation of the coupling interface for obtaining highly active heterostructured catalysts for overall water splitting.

The rational design and development of cost-effective and high-efficiency bifunctional electrocatalysts for overall water splitting is of prime significance for advancing large-scale commercial hydrogen production. Herein, a novel nanoporous NiAl layered double hydroxide nanosheet array with optimized Ni active sites on nickel foam (np-NiAl-LDH/NF) is prepared by a facile and simple metal-defect engineering strategy. We demonstrate that the partial leaking of catalytically inactive Al sites in NiAl-LDH nanosheets during anodic electrochemical etching can not only trigger the generation of a nanoporous structure and electron-rich Ni²⁺ sites, but can also increase the content of Ni³⁺ active sites accompanied by abundant oxygen defects, resulting in the synchronously increased density and intrinsic activity of Ni active sites and also enhanced mass and electron transport, thus greatly promoting the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. As expected, the as-obtained np-NiAl-LDH/NF electrode needs extremely small overpotentials of 90 and 180 mV to deliver the 10 mA cm⁻² current density for the HER and OER in alkaline media, respectively. Moreover, an alkaline electrolyzer assembled with np-NiAl-LDH/NF functioning as both the anode and cathode can yield 10 and 100 mA cm⁻² at quite low voltages of ∼1.5 and 1.7 V, respectively, far outperforming the Pt/C/NF–IrO₂/NF-coupled electrolyzer, and can give durable stability for at least 60 h. This work provides new insights for creating highly efficient Ni-based electrocatalysts toward overall water splitting via engineering on catalytically active Ni sites.

Developing efficient and low-cost bifunctional electrocatalysts as candidates for Pt-based materials to satisfy commercial applications in the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is still very challenging. Herein, we show that Co,N-codoped porous vanadium nitride (VCoN) nanoplates are successfully synthesized via a simple one-step pyrolysis protocol without the use of NH₃ gas. We also demonstrate that the crystallization, surface chemical state and porosity of vanadium nitride are well modulated by inventively using Co dopants as structural inducers. The resulting VCoN material exhibits an excellent catalytic activity towards the HER in alkaline media, with an extremely low onset potential of −0.03 V, an overpotential of 179 mV at 10 mA cm⁻², and a remarkable durability for over 100 h. Moreover, it shows a superior ORR performance, which compares favorably with commercial 20% Pt/C, exhibiting an onset potential of ∼1.02 V, a half-wave potential of ∼0.91 V and a weak potential shift (−5 mV) after 2000 cycles at 1600 rpm in 0.1 M KOH. Such excellent electrocatalytic performance primarily contributes to the unique structural features of the heteroatom N (pyrrolic and graphitic N) and Co codoping in favor of improving the electrical conductivity and the high porosity contributing to exposing numerous catalytic active sites.