Core-Shell Ru/NiOx@graphene Composite Aerogel as efficient Bifunctional Electrocatalysts for Overall Water Splitting

Abstract

The development of bifunctional catalysts with excellent catalytic properties is the main task for alkaline electrolytic water, and hence the construction of a novel crystalline/amorphous heterojunction catalysts is proved to be an effective strategy to realize bifunctional electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction(OER). In this paper, uniformly dispersed and highly active Ru/NiOx heterojunction anchored on the GA composites (Ru/NiOx@GA) were successfully synthesized by freeze-drying and calcination process. The results of XRD, TEM, and XPS tests show that there were strong interactions in the Ru/NiOx heterojunction and graphene, and the NiOx in the outer layer exert a squeezing effect on the Ru in the inner layer that generate charge transfer from Ni to Ru. As such, the Ru/NiOx@GA only requires a overpotentials of only 34 mV (HER) and 237 mV (OER) when reaching a current density of 10 mA cm-2 in 1 M KOH electrolyte, as well as display a roust cycling stability of over 200 h. A low decomposition voltage of 1.53 V and a high Faraday efficiency of 100% were obtained for the assembled overall water splitting (OWS) device. All these are attributed to the synergistic effect of between Ru/NiOx heterojunction resulting in charge-enriched Ru sites and oxidation state-corrected Ni site, as well as high conductivity of GA. This study highlights the unique advantages of the synergistic effect of both crystalline/amorphous heterojunctions and GA, which provides a new way to prepare GA-based materials for advanced multifunctional electrocatalytic applications.