{1̄11} faceted Ni ₃ S ₂ with an asymmetric zigzag structure is elaborately designed and fabricated, which exhibits remarkable electrocatalytic performance for the HER and OER.

Designing low-cost and high-active bifunctional catalysts for overall water splitting has attracted increasing research interest. Herein, the brilliant overall water splitting performance of cobalt–vanadium bimetal-based nanocomposites is explored. Co–V based nanocomposites are synthesized through a one-step hydrothermal method, in which the cobalt species is introduced into the lepidocrocite VOOH and further cobalt vanadium oxide is formed. The additive level of cobalt is optimized and the corresponding effect on electrocatalytic activity is also investigated in this work, systematically. The targeted catalyst (denoted as Co_0.2-VOOH) exhibits a unique sheet-like morphology, resulting in the high exposure of catalytically active sites. When used as the bifunctional catalyst, Co_0.2-VOOH can achieve a current density of 10 mA cm⁻² at the overpotentials of 210 mV for water oxidation and 130 mV for hydrogen generation, respectively. Notably, it only requires low cell voltages of 1.57 and 1.74 V to drive the catalytic current densities of 10 and 100 mA cm⁻² during the water splitting process. This work significantly indicates that cobalt–vanadium based materials are promising alternatives for overall water splitting.

Through hydro- and solvothermal methods and an electrodeposition-assisted in situ growth strategy, a transition metal disulfide (TMD)-assembled heterostructural cathode (Ni₃S₂/MoS₂-CC) and derivative TMD superficial amorphous bimetallic hydroxide-coated anode (NiFe(OH)_x@Ni₃S₂/MoS₂-CC) were successfully prepared for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. The synthesized electrodes demonstrate first-rate performance with enhanced durability for electrolysis. Individually, Ni₃S₂/MoS₂-CC affords an overpotential (η) of 173 mV (at 100 mA cm⁻²) in HER, while NiFe(OH)_x@Ni₃S₂/MoS₂-CC affords an η of 309 mV (at 100 mA cm⁻²) in OER. Tight interstratification between the nanosheet (NS) array and amorphous bimetallic hydroxides lead to enhanced affinity for OH⁻/H⁺, improved conductivity, increased charge transfer, and enriched active sites. The two-electrode alkaline (1.0 M KOH) electrolyzer (NMC//NFNMC) requires a low overall voltage (ΔV) of 1.55 and 1.71 V to reach 10 and 100 mA cm⁻², respectively. The rational combination of TMDs and TMDs/NiFe(OH)_x delivers a useful methodology for designing and constructing low-cost, hierarchical, transition metal-based composite catalysts with high performance for water electrolysis.