Decoupled electrolysis has proven to be a novel method for safe hydrogen production, but improvement is still possible. Redox mediators allow us to produce H2 and O2 in separate time and space, avoiding explosive gas mixtures. A critical factor in developing new redox mediators is the availability of the material and non-toxicity. Traditionally used acidic solid-state redox mediators are V2O5, WO3 and MoO3, but they are relatively scarce and unavailable in the EU; that is why developing new materials, in this case- TiO2, is essential. Here, we demonstrate a decoupled electrolysis system with TiO2 quantum dots of 4.5 nm as an efficient redox mediator in acidic electrolytes. TiO2 nanoparticles showed a high electrochemical surface area on carbon felt supported, with a specific capacity of 375 F/g, ten times larger than commercially available TiO2 P25 nanoparticles. During the O2 production cycle, H+ ions intercalated in the TiO2 redox mediator, forming Ti3+, as demonstrated by XPS results and observable colour change. Produced electrodes showed high stability even after 3000 cycles with an overall energy efficiency of 52.4% and gas purity above 98%. These results demonstrate the perspective of TiO2 as a possible alternative to well-established redox mediators for decoupled electrolysis. Decoupled electrolysis with cheap and abundant redox mediators can provide a viable alternative to membrane electrolysers, eliminating the need for expensive membranes and extensive pressure-equalising systems.