Cobalt Iron Hydroxide as a Precious Metal‐Free Bifunctional Electrocatalyst for Efficient Overall Water Splitting

Highly efficient and stable electrocatalysts from inexpensive and earth‐abundant elements are emerging materials in the overall water splitting process. Herein, cobalt iron hydroxide nanosheets are directly deposited on nickel foam by a simple and rapid electrodeposition method. The cobalt iron hydroxide (CoFe/NF) nanosheets not only allow good exposure of the highly active surface area but also facilitate the mass and charge transport capability. As an anode, the CoFe/NF electrocatalyst displays excellent oxygen evolution reaction catalytic activity with an overpotential of 220 mV at a current density of 10 mA cm−2. As a cathode, it exhibits good performance in the hydrogen evolution reaction with an overpotential of 110 mV, reaching a current density of 10 mA cm−2. When CoFe/NF electrodes are used as the anode and the cathode for water splitting, a low cell voltage of 1.64 V at 10 mA cm−2 and excellent stability for 50 h are observed. The present work demonstrates a possible pathway to develop a highly active and durable substitute for noble metal electrocatalysts for overall water splitting. A synthesized CoFe/NF electrode exhibits efficient electrocatalytic activity for OER and HER. The higher catalytic activity of CoFe/NF is attributed to synergistic effects between Co and Fe as cooperating active sites. The CoFe/NF films used as bifunctional catalysts for overall water splitting could achieve a current density of 10 mA cm−2 at 1.64 V and excellent stability for 50 h.