Ultra-thin hierarchical porous carbon coated metal phosphide self-assembled efficient tri-functional electrodes for overall water splitting and rechargeable zinc-air batteries

Highly efficient and stable trifunctional electrocatalysts with controllable nanostructures toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are extraor-dinarily important for the sustainable energy development. Here we report a general and facile synthetic method for designing a hierarchically porous Ni-foam-based self-supported electrode (NPO/NixPy@NF-HPCs). Based on its unique design concept, the NPO/NixPy@NF-HPCs shows high tri-functional catalytic activities. As a result, the NPO/NixPy@NF-HPCs-based rechargeable zinc-air battery (ZAB) and water splitting device exhibit high power density up to 377 mW cm-2 and low cell voltage of 1.52 V@10 mA cm-2, respectively. Notably, the mapping between the stability and the quasi-in situ characterization demonstrates that it is a reliable method to improve electrode stability by establishing a stable outer carbon layer to avoid the oxidation of internally active sites. This work is promised to provide a viable new approach to developing efficient and low-cost carbon-supported phosphate tri-functional electrode.