Bifunctional Substrates: In‐situ Ni, Fe co‐doped Cobalt Carbonate Hydroxides for Overall Water Splitting

Developing highly efficient and stable electrocatalysts with large current densities for hydrogen and oxygen evolution is still challenging. Herein, Ni and Fe co‐doped cobalt carbonate hydroxide catalysts were designed in situ on the three‐dimensional porous NiFe foam through a facile one‐step hydrothermal strategy. Inductively coupled plasma atomic emission spectrum, transmission electron microscopy‐element mapping, X‐ray photoelectron spectroscopy, and DFT calculations demonstrate that the three‐dimensional NiFe foam substrate not only serves as the porous substrate, which enhances the exposed number of active sites, but also enhances the intrinsic activities of single active sites via introducing Ni and Fe dopants in the cobalt carbonate hydroxide catalyst during the hydrothermal process. The obtained hybrid electrocatalyst can be employed as a highly efficient and stable bifunctional electrocatalyst for the oxygen and hydrogen evolution reactions, with overpotentials of 340 mV and 371 mV at 1000 mA cm−2, respectively. In addition, tests in an alkaline electrolyzer revealed that the current density could reach 1000 mA cm−2 at a voltage of 2 V and maintain stable operation for 100 h. Our study presents experimental evidence of the significant role of the catalyst substrate in the hydrothermal reaction, offering novel ideas for improving the catalyst performance. The fabricated Ni and Fe co‐doped cobalt carbonate/NiFe electrode shows superior OER and HER bifunctional electrocatalytic performance, revealing potential commercial opportunities in overall water splitting.