Fullerene-Buffered Electron Shuttle of Ru/RuO with Switchable Active Sites Enables Robust and Efficient Bifunctional Alkaline Water Electrolysis.

Developing highly-efficient and robust bifunctional electrocatalyst for overall water splitting (OWS) is desirable, but it confronts long-term challenge in the local structural reconstruction of catalyst during the hydrogen and oxygen evolution reaction (HER and OER). As inspired by the stable acid-base buffer system in human life, here we construct an electron buffer system to well address the key issue of structural reconstruction, in which the charge-buffered fullerene renders Ru-based active species to be reversibly shuttled between Ru and RuO during HER and OER. Consequently, the as-prepared Ru-RuO/C catalyst exhibits overpotentials of merely 7 and 194 mV at 10 mA cm for HER and OER in alkaline conditions, respectively. The photovoltaic-driven OWS device with a solar-to-hydrogen (STH) efficiency of 18.9% and an anion exchange membrane water electrolysis (AEMWE) system with good robustness was fabricated based on Ru-RuO/C . It was unraveled by in situ/operando spectroscopy and theoretical calculation that the significantly promoted performance of water electrolysis benefits from the fullerene-based electron shuttle effect on inhibition of structural reconstruction and electronic structural modulation of active sites as well as adsorption energy of the reaction intermediates. Our work may open an avenue to develop efficient and robust bifunctional electrocatalyst for promising industrial water electrolysis.