Rhodium phosphide ultrathin nanosheets for hydrazine oxidation boosted electrochemical water splitting

[Display omitted] •Rh2P ultrathin nanosheets (Rh2P uNSs) with atomic thickness (1.5 nm) and big surface area (55.0 m2 g−1) are successfully synthesized.•Rh2P uNSs show excellent activity for both hydrogen evolution reaction and hydrazine oxidation reaction (HzOR).•The acidic electrolyte can restrain the undesirable chemical decomposition pathway of N2H4 and avoid the poisoning effect during HzOR.•Rh2P uNSs||Rh2P uNSs electrolyzer only requires electrolysis voltage of 0.377 V for HzOR boosted electrochemical water splitting. Optimizing component and morphology of precious metal nanomaterials can effectively promote their electrocatalytic performance and expand their application area. In this work, Rh2P ultrathin nanosheets (Rh2P uNSs) with atomic thickness and big surface area are successfully synthesized by phosphating treatment of Rh ultrathin nanosheets (Rh uNSs). Benefiting from special morphology, component, and electronic structure, Rh2P uNSs simultaneously display enhanced electrocatalytic activity for anodic hydrazine oxidation reaction (HzOR) as well as cathodic hydrogen evolution reaction (HER) compared to Rh uNSs in acidic media, which only require at −10 mV and 300 mV potential to obtain 10 mA cm−2 current density for HzOR and HER in three electrode system, respectively. In two electrode system, the symmetric Rh2P uNSs||Rh2P uNSs electrolyzer only requires electrolysis voltage of 0.377 V to achieve 10 mA cm−2 current density for HzOR boosted water splitting in strong acidic media, highlighting an energy-saving electrochemical hydrogen production method.