Lacunary polyoxometalate oriented construction of dispersed NiS confined in WO for electrocatalytic water splitting.

Manufacturing low-cost, high-performance and earth-rich catalysts for hydrogen evolution (HER) and oxygen evolution reactions (OER) is critical to achieving sustainable green hydrogen production. Herein, we utilize lacunary Keggin-structure [PWO] (PW) as a molecular pre-assembly platform to anchor Ni within a single PW molecule by vacancy-directed and nucleophile-induced effects for the uniform dispersion of Ni at the atomic level. The chemical coordination of Ni with PW can avoid the aggregation of Ni and favor the exposure of active sites. The NiS confined by WO prepared from controlled sulfidation of NiPW/Nickel Foam (NiPW/NF) exhibited excellent catalytic activity in both 0.5 M HSO and 1 M KOH solutions, which required only 86 mV and 107 mV overpotentials for HER at a current density of 10 mA∙cm and 370 mV for OER at 200 mA∙cm. This is attributed to the good dispersion of Ni at the atomic level induced by trivacant PW and the enhanced intrinsic activity by synergistic effect of Ni and W. Therefore, the construction of active phase from the atomic level is insightful to the rational design of dispersed and efficient electrolytic catalysts.