Hierarchical Ni@CNTs-bridged MoxC/Ni2P heterostructure micro-pillars for enhanced seawater splitting and Mg/seawater battery

Abstract

In this study, a high-efficiency hybrid catalyst of Ni nanoparticles-encapsulated carbon nanotubes-bridged molybdenum carbide/nickel phosphide heterostructures (Ni@CNTs-MoxC/Ni2P) is prepared via a facile synthesis route. The catalyst having hierarchical structure with rich heterogeneous interfaces of MoxC/Ni2P micro-pillars bridged with Ni@CNTs offers an efficient connection among different active phases to guarantee good conductivity and stability. It also results in large electroactive surface with abundant multiple electroactive sites and creates unique modified electronic properties to effectively increase density of states near the Femi level and well adjust adsorption free energy, thus highly beneficial to simultaneously promote bifunctional OER and HER performances. The Ni@CNTs-MoxC/Ni2P only requires small overpotentials of 54 mV for HER and 228 for OER at 10 mA cm–2 in alkaline electrolyte, superior to recently reported bifunctional catalysts. The electrolyzer cell of Ni@CNTs–MoxC/Ni2P(+,-) requires a low operating voltage of 1.53 and 1.56 V at 10 mA cm–2 in alkaline freshwater and natural seawater, respectively. The Mg/seawater battery from Ni@CNTs–MoxC/Ni2P-based cathode exhibits a high peak power density of 7.01 mW cm−2 with a stable discharge period of 100 h. The results suggest that Ni@CNTs-MoxC/Ni2P is a promising candidate for future seawater splitting and prospective Mg/seawater battery application.