Hierarchically assembling cobalt/nickel carbonate hydroxide on copper nitride nanowires for highly efficient water splitting

[Display omitted] •Cu3N@CoNiCHs heterostructures are fabricated as bifunctional electrocatalysts for HER and OER in alkaline electrolyte.•Cu3N@CoNiCHs integrate merits including abundant active sites, rapid charge transfer, and modulated electronic structure.•The dual-phase transformation of Cu3N@CoNiCHs during electrolysis provides active sites for HER and OER, respectively.•The Cu3N@CoNiCHs not only exhibit excellent HER and OER performance but also accelerate overall water splitting. The intensive pursuit of cost-effective electrocatalysts capable of enabling highly efficient and stable water splitting comprised of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is quite imperative but challenging. Herein, a 3-dimensional (3D) hierarchical architecture consisted of copper nitride (Cu3N) and Co-Ni carbonate hydroxides (CoNiCHs) on copper foam (CF) was synthesized, and the Cu3N@CoNiCHs@CF requires quite small overpotentials (ηs) of 182 and 155 mV to afford current density (j10) of 10 mA cm−2 for HER and OER, respectively. More importantly, it requires a comparably low potential of 1.58 V to deliver j10 upon driving overall water splitting due to an optimal integration of the 3D hierarchical configuration and the desirable interface interplay of Cu3N and CoNiCHs, outperforming those of noble metals and most of the benchmarking bifunctional electrocatalysts. This study paves an attractive way to better unraveling the interface interplay over hierarchical architectures with very promising electrocatalytic activity.