Bicontinuous RuO2 nanoreactors for acidic water oxidation

Improving activity and stability of Ruthenium (Ru)-based catalysts in acidic environments is eager to replace more expensive Iridium (Ir)-based materials as practical anode catalyst for proton-exchange membrane water electrolyzers (PEMWEs). Here, a bicontinuous nanoreactor composed of multiscale defective RuO 2 nanomonomers (MD-RuO 2 -BN) is conceived and confirmed by three-dimensional tomograph reconstruction technology. The unique bicontinuous nanoreactor structure provides abundant active sites and rapid mass transfer capability through a cavity confinement effect. Besides, existing vacancies and grain boundaries endow MD-RuO 2 -BN with generous low-coordination Ru atoms and weakened Ru-O interaction, inhibiting the oxidation of lattice oxygen and dissolution of high-valence Ru. Consequently, in acidic media, the electron- and micro-structure synchronously optimized MD-RuO 2 -BN achieves hyper water oxidation activity (196 mV @ 10 mA cm −2 ) and an ultralow degradation rate of 1.2 mV h −1 . A homemade PEMWE using MD-RuO 2 -BN as anode also conveys high water splitting performance (1.64 V @ 1 A cm −2 ). Theoretical calculations and in-situ Raman spectra further unveil the electronic structure of MD-RuO 2 -BN and the mechanism of water oxidation processes, rationalizing the enhanced performance by the synergistic effect of multiscale defects and protected active Ru sites. Developing stable water oxidation catalysts is of great importance for proton-exchange membrane water electrolyzers. Here the authors report a bicontinuous nanoreactor composed of multiscale defected RuO 2 nanocrystals for robust acidic water oxidation reactivity.