Ru Single Atoms and Sulfur Anions Dual‐Doped NiFe Layered Double Hydroxides for High‐Current‐Density Alkaline Oxygen Evolution Reaction

Abstract New anodic electrocatalysts with high performance and cost‐effectiveness at large current densities help advance the emerging anion exchange membrane water electrolyzer (AEMWE) technology. To this end, a ruthenium (Ru) single atoms and sulfur (S) anions dual‐doped NiFe layered double hydroxides (Ru‐S‐NiFe LDH) catalyst is reported with remarkably low alkaline oxygen evolution reaction (OER) overpotentials, high mass activities and prolonged stabilities at high current densities. Inspiringly, the AEMWE performance on Ru‐S‐NiFe LDH is also superior to the NiFe LDH. In‐depth mechanism investigations reveal that Ru single atoms not only act as the highly active sites, but also facilitate the conductivity of NiFe LDH. Meanwhile, S anions accelerate the electrochemical reconstruction of NiFe LDH to OER‐active NiFeOOH and alleviate the over‐oxidation issue on Ru active sites. Benefiting from these, Ru‐S‐NiFe LDH shows significantly enhanced OER activity and stability. Theoretical calculations further validate the decreased OER free energy difference brought about by the Ru single atoms and S anions dual‐doping. This study offers a proof‐of‐concept that the noble metal single atoms and anions dual‐doping is a feasible strategy to construct the promising 3 d transition metal‐based electrocatalysts toward the practical alkaline water electrolyzer.