Electrosynthesis of NiFe Layered Double Hydroxides with Gradient Structure for Oxygen Evolution Reaction

Well-designed gradient electrodes often possess both good structural stability and high electrochemical activity. Herein, NiFe layered double hydroxide (NiFe LDH)-based gradient electrode was fabricated by two-step electrodeposition on nickel foam (NF) at different potentials (gradient potential method) with the assistance of O 2 . The NiFe LDH with gradient structure and composition displayed higher catalytic activity for oxygen evolution reduction (OER) and better long-term stability than the uniform NiFe LDH. At a current density of 50 mA cm −2 , the overpotential of the optimum NiFe LDH based gradient electrode (G(1/4)-NiFe LDH) is only 295 mV. To achieve 10 mA cm −2 , the voltage required by G(1/4)-NiFe LDH based electrolytic cell for overall water splitting is 1.52 V. In addition, the important role of O 2 in the electrodeposition process was studied in detail. The O 2 -assisted gradient potential method is also applicable for the synthesis of other LDHs such as NiCo LDH and NiAl LDH. This study provides a facile and effective method to prepare LDHs with gradient structure and excellent OER performance.