Hollow Nanocages of NixCo1-xSe for Efficient Zinc-Air Batteries and Overall Water Splitting

HighlightsA facile strategy for fabricating NixCo1-xSe hollow nanocages was developed, and the formation mechanism was well explained.Ni0.2Co0.8Se outperformed a Pt/C+RuO2 catalyst in rechargeable and all-solid-state Zn-air battery tests, as well as in overall water splitting.The hydrogen adsorption onto NixCo1-xSe was simulated, and Gibbs free energies were calculated. AbstractDeveloping Earth-abundant, highly efficient, and anti-corrosion electrocatalysts to boost the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) for the Zn-air battery (ZAB) and for overall water splitting is imperative. In this study, a novel process starting with Cu2O cubes was developed to fabricate hollow NixCo1-xSe nanocages as trifunctional electrocatalysts for the OER, ORR, and HER and a reasonable formation mechanism was proposed. The Ni0.2Co0.8Se nanocages exhibited higher OER activity than its counterparts with the low overpotential of 280mV at 10mAcm(-2). It also outperformed the other samples in the HER test with a low overpotential of 73mV at 10mAcm(-2). As an air-cathode of a self-assembled rechargeable ZAB, it exhibited good performance, such as an ultralong cycling lifetime of>50h, a high round-trip efficiency of 60.86%, and a high power density of 223.5mWcm(-2). For the application in self-made all-solid-state ZAB, it also demonstrated excellent performance with a power density of 41.03mWcm(-2) and an open-circuit voltage of 1.428V. In addition, Ni0.2Co0.8Se nanocages had superior performance in a practical overall water splitting, in which only 1.592V was needed to achieve a current density of 10mAcm(-2). These results show that hollow NixCo1-xSe nanocages with an optimized Ni-to-Co ratio are a promising cost-effective and high-efficiency electrocatalyst forZABs and overall water splitting in alkaline solutions.