Nanoporous Sulfur-Doped Copper Oxide (Cu₂O_xS_1-x) for Overall Water Splitting

Developing active and bifunctional noble metal-free electrocatalysts is crucial for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the full water splitting process. A ternary nanoporous sulfur-doped copper oxide (Cu₂O_xS_1-x) was successfully synthesized on Cu foam. The obtained Cu₂O_xS_1-x/Cu shows robust electrocatalytic activity toward HER with a low overpotential of 40 mV at 10 mA cm^-2 and a Tafel slope of 68 mV dec^-1 and exhibits long-term stability in acid solution. Moreover, Cu₂O_xS_1-x shows excellent electrocatalytic activity for OER, HER, and overall water splitting as a bifunctional catalyst in 1.0 M KOH electrolyte. The sulfur doping strategy implemented here can greatly improve the catalytic performance and stability in both acidic and alkaline water electrolyzers and presents an efficient catalyst for overall water splitting.