Engineering of interface-assisted oxygen vacancies to enhance electrode activity in aqueous anthraquinone redox flow...

Sluggish redox kinetics at the carbon felt (CF) anode hinder the large-scale application of aqueous organic redox flow batteries (AORFBs) that employ anthraquinone derivatives as anolytes. Although the use of transition metal oxide catalysts, particularly those with oxygen vacancies, could overcome this limitation, their potential capability and catalytic mechanisms remain underexplored. In this study, a self-assembled MoO_3-x/MXene heterostructure was designed for the first time for use in AORFBs. The MoO_3-x/MXene-modified CF electrode exhibited a markedly enhanced electrochemical activity. At a 50 % state of charge, the battery with the MoO_3-x/MXene/CF electrode delivered power densities that were 27.4 % and 79.1 % higher than those in batteries with MXene/CF and MoO_3-x/CF electrodes, respectively. Experimental and theoretical results demonstrated that the high catalytic activity of the heterostructure stemmed from the optimization of oxygen vacancy engineering via the synergistic effect between interface reconstruction and the electric field, both of which were induced by the interfacial asymmetric chemical potential. This synergy increased the population of highly intrinsic active oxygen vacancy sites and activated additional active sites by ameliorating inherent conductivity defects. This study elucidates the mechanism by which oxygen vacancies accelerate the redox kinetics of the anode and proposes an interfacial asymmetric chemical potential-assisted oxygen vacancy engineering strategy to develop high-performance electrocatalysts for AORFBs.