Electrochemical construction of Cu@NF frameworks and synthesis of self-supported microflower Cu₂S@NF as bifunctional catalysts for overall water splitting

A two-step electrochemical method is proposed for the in-situ deposition of copper and synthesis of copper(Ⅰ) sulfide (Cu₂S) with controllable morphology on nickel foam (NF), and the thus-prepared self-supported Cu₂S@NF electrodes exhibit excellent performance as bifunctional electrocatalysts. Characterizations with scanning electron microscopy show rock-shape of the deposited copper through potentiostatic method, which can be further sulfurized to microflower morphology by a unique underpotential electrochemical method. The size and amount of the deposits can be adjusted by controlling applied potentials, leading to the optimization of electrocatalytic activity. The Cu₂S@NF exhibits superior electrocatalytic performance towards HER and OER in 1 M KOH with the low overpotentials of 105 mV and 194 mV at 10 mA/cm², as well as small Tafel slopes of 92.89 mV/dec and 72.81 mV/dec, respectively. This work provides a simple method for the synthesis of efficient catalysts, which can be extended to the fabrication of other transition metal-based electrocatalysts.