The Role of Proton in High Power Density Vanadium Redox Flow Batteries.

To design high-performance vanadium redox flow batteries (VRFBs), the influence of proton on electrocatalysts cannot be neglected considering the abundance of proton in a highly acidic electrolyte. Herein, the impact of proton on metal oxide-based electrocatalysts in VRFBs is investigated, and a proton-incorporating strategy is introduced for high power density VRFBs, in addition to unraveling the catalytic mechanism. This study discloses that the metal oxide-based electrocatalyst (WO 3 ) undergoes in situ surface reconstruction by forming H 0.5 WO 3 after incorporating proton. Experimental and theoretical results precisely disclose the catalytic active sites. The battery with H 0.5 WO 3 designed by a proton-incorporating strategy achieves an attractive power density of 1.12 W cm -2 and sustains more than 900 cycles without an obvious decay, verifying the outstanding electrochemical performance of H 0.5 WO 3 . This work not only sheds light on the influence of proton on electrocatalysts for rational design of advanced VRFBs catalysts but also provides guidelines for the fundamental understanding of the reaction mechanism, which is highly important for the application of VRFBs.