Site Activity and Population Engineering of NiRu-Layered Double Hydroxide Nanosheets Decorated with Silver Nanoparticles for Oxygen Evolution and Reduction Reactions

Developing efficient and durable bifunctional electrocatalysts for oxygen reduction and evolution reaction (ORR/OER) is highly desirable in energy conversion and storage systems. This study prepares nickel−ruthenium layered double hydroxide (NiRu-LDHs) nanosheets subjected to decoration with conductive silver nanoparticles (Ag NP/ NiRu-LDHs), which interestingly induce their multivacancies associated with catalytic site activity and populations. The as prepared Ag NP/NiRu-LDH shows excellent catalytic activity toward both OER and ORR features with low onset overpotentials of 0.21 V and −0.27 V, respectively, with a 0.76 V potential gap between OER potential at 10 mA cm−2 and ORR potential at −3 mA cm−2 , demonstrating that it is the preeminent bifunctional electrocatalyst reported to date. Compared with pristine NiRu-LDHs, the resulting Ag NP/NiRu LDHs nanosheets require only an overpotential of 0.31 V to deliver 10 mA cm−2 with excellent durability. The superb bifunctional performance of Ag NP/NiRu-LDH is ascribed to the formation of multivacancies, mutual benefits of synergistic effect between metal LDHs and silver nanoparticles, and increased accessible active sites together with site activity are the key to the perceived performance. This work provides a new strategy to decorate LDHs and to engineer multivacancies to enhance site activity and populations simultaneously as ORR/OER bifunctional electrocatalysts.