Doping and heterostructure engineering regulated I-Ni(OH)2/Co(OH)2@nickel foam charge buffer electrode for decoupled and alternating water splitting

Abstract

The integration of a two-step, alternating hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) within a water splitting system is of paramount importance, enabling economically feasible and substantial production of molecular hydrogen. In this investigation, an extensive strategy involving doping and heterostructure engineering was implemented to fabricate the I-Ni(OH)2/Co(OH)2 @nickel foam (NF) charge buffer electrode. This electrode acted as a proficient charge mediator, effectively decoupling the simultaneous OER and HER. Notably, the initial HER process at the cathodic electrode demonstrated impressive efficacy, yielding a continuous 1500-second hydrogen evolution cycle at a current of 0.1 amperes. Concurrently, the as-developed I-Ni(OH)2/Co(OH)2 @NF experienced oxidation, transitioning to its corresponding oxidized form and reaching a remarkable operational voltage of 1.572 V. Following this, the OER process revitalized the charge mediator, facilitating anodic oxygen generation at the operational voltage of 0.33 V with equivalent gas production time. Additionally, combining an oxidizing mediator with a Zn sheet facilitated battery formation, effectively substituting the second OER stage. This innovative integration allowed for prolonged H2-production and battery discharge simultaneously, affording a novel avenue to H2-generation that obviates the necessity for an external power source. Therefore, this apparatus, decoupling the HER-OER processes, proposes a promising approach to effectively convert sustainable resources into H2.