La and S Co-Doping Induced the Synergism of Multiphase Nickel-Iron Nanosheets with Rich Oxygen Vacancies to Trigger Large-Current-Density Oxygen Evolution and Urea Oxidation Reactions.

The development of cost-effective electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is of great significance for hydrogen production. Herein, La and S co-doped multiphase electrocatalyst (LSFN-63) is fabricated by metal-corrosion process. FeOOH can reduce the formation energy of NiOOH, and enhance the stability of NiOOH as active sites for OER/UOR. The rich oxygen vacancies can increase the number of active sites, optimize the adsorption of intermediates, and improve electrical conductivity. Beyond, La and S co-doping can also regulate the electronic structure of FeOOH. As a result, LSFN-63 presents a low overpotential of 210/450 mV at 100/1000 mA cm , small Tafel slope (32 mV dec ), and outstanding stability under 1000 mA cm @60 h, and can also display excellent OER activity with 180 mV at 250 mA cm and long-term catalytic durability at 250 mA cm @135 h in 30 wt% KOH under 60 °C. Moreover, LSFN-63 demonstrates remarkable UOR performance in 1 m KOH + 0.5 m urea, which just requires an ultra-small overpotential of 140 mV at 100 mA cm , and maintain long-term durability over 120 h. This work opens up a promising avenue for the development of high-efficiency electrocatalysts by a facile metal-corrosion strategy.