Electrocatalytic water splitting with unprecedentedly low overpotentials by nickel sulfide nanowires stuffed into carbon nitride scabbards

Electrocatalytic water splitting to oxygen and hydrogen has much attention as one of the most promising approaches for sustainable production of hydrogen as a carbon-neutral fuel. To establish efficient electrocatalytic water splitting, the overall overpotential for this reaction must be minimized via developing efficient catalysts to promote oxygen and hydrogen evolution at the anode and the cathode, respectively. However, the overpotentials (ηO210) for oxygen evolution are insufficiently low (180-300 mV for a current density of 10 mA cm-2), and the ηO210 value less than 100 m still remains untracked. Here we report the unprecedentedly low ηO210 of 32 mV for oxygen evolution attained by forming a unique motif of nickel sulfide nanowires stuffed into carbon nitride scabbards (NiSx/C3N4), demonstrating electrocatalytic water splitting at the lowest overall overpotential of 72 mV using the NiSx/C3N4 anode. This motif provides a key of a guided thought to develop efficient catalysts for oxygen evolution.