The electrochemical synthesis of CNTs/N-Cu₂S composites as efficient electrocatalysts for water oxidation

Oxygen evolution reaction (OER) catalysts are of central importance for electrocatalytic water oxidation and fuel generation, while it is still an urgent requirement to design and develop efficient OER catalysts with rapid kinetics and low overpotentials. Herein, we report an electrochemical deposition method to fabricate carbon nanotubes/N-doped cuprous sulfide (CNTs/N-Cu₂S) composites using thiourea and a CuSO₄ solution as the S and Cu sources, respectively. The advantages of this strategy include low cost, simple processing and the absence of templates or surfactants that can otherwise affect the electrochemical properties of the products. The N supplied by the thiourea can be used as a doping agent as a result of the in situ formation of small N-Cu₂S particles, which can increase larger surface area and create more active sites to enhance OER catalytic activity, compared with that obtained with materials synthesized without adding the thiourea. The synergic interface of CNTs and N-Cu₂S can improve conductivity and efficient chemical transfer in the composites electrodes by introducing CNTs. Under the optimal experimental conditions, the CNTs/N-Cu₂S-5cyc composites present an excellent activity with the current density of 10 mA cm⁻² at a low OER overpotential of 280 mV, the Tafel slope of 63 mV dec⁻¹ and a strong electrochemical stability in 1.0 M KOH solution.