Cobalt Polyoxometalates Anchored on Nife-LDH Nanoplates as Highly Active and Stable Bifunctional Catalysts for Overall Water Splitting

Designing efficient and bifunctional electrocatalysts for water splitting conforms to the concept of energy conservation and emission reduction but remains challenging now. Herein, the fabrication of a heterostructure by anchoring cobalt-polyoxometalates (Co-POM) on NiFe layered double hydroxide (NiFe-LDH) nanoplates in situ on nickel foam (NF) is first reported (Co-POM@LDH/NF). The surface area, electron transfer ability, and stability of the heterostructure are increased due to the synergistic effect between Co-POM and NiFe-LDH. Particularly, Co-POM@LDH/NF can deliver a current density of 100 mA cm-2 with an overpotential of only 220 mV for hydrogen evolution reaction (HER) and 226 mV for oxygen evolution reaction (OER) in 1.0 m KOH electrolytes. Impressively, the outstanding stability of Co-POMs in heterostructures is verified by the experimental observations after electrolysis, indicating the successful construction of stable POMs-based heterogeneous electrocatalysts. More attractively, the electrolyzer composed by Co-POM@LDH/NF as anode and cathode shows a much lower operating voltage of 1.51 V at the current density of 10 mA cm-2 for overall water splitting. This study provides a feasible and extensible idea for the design of the POM-based heterostructures. A novel cobalt-polyoxometalates (Co-POMs) on layered double hydroxide (LDH) heterostructure is demonstrated, which exhibits outstanding catalytic activity and long-term durability toward alkaline overall water splitting. And the excellent electrocatalytic performance and the outstanding stability of Co-POMs in heterostructures are attributed to the synergistic effect between Co-POMs and LDH. This work presents a new strategy for fabricating stable POM-based heterostructure with excellent catalytic activity.image