Highly efficient and robust sulfur-doped nickel-cobalt oxide towards oxygen evolution reaction

A superior catalytic system for oxygen evolution reaction (OER) is developed utilizing a sulfur doping strategy to boost the intrinsic catalytic property of crystalline nickel-cobalt oxide. By varying the sulfur doping duration, the sulfur doping ratios can be altered, the morphology changed from nanorod to nanosheet, the defect oxygen density may be varied, and the electronic state can be modulated. The electronic state modification is identified to be predominant, while morphology and defect oxygen changes contribute to the promoted OER performance to certain degree. The S-NiCoOx-5 h sample possesses an optimum density of state near the Fermi level and the enlarged electrochemical active surface area, endowing a superior OER performance as indicated by the satisfactory 221 mV of overpotential required at 10 mA/cm2. After integration with our earlier-developed HER-active NiCo-based phosphate catalyst, a remarkable 1.61 V is obtained to drive the overall water splitting to reach 10 mA/cm2 in 1 M KOH. This work highlights the promotion effect of S incorporation for OER and offers a robust and efficient catalytic system for practical hydrogen production through water electrolysis.