context: Up to now, owing to the tremendous work done by different research groups, there have been several new types of electrolysers proposed for decoupled H2/O2 generation through the utilization of redox mediators, and a list of these new electrolysers has been provided in Table S1 in the ESI.† For example, a new PEM electrolyser is proposed with polyoxometalates (POMs) used as the redox relay, and the H2/O2 generation can be decoupled both in time and in space (Scheme 1b). Such a design requires three electrodes (OER electrode, carbon electrode for reduction of the soluble POM redox mediator, and Pt catalyst for spontaneous hydrogen evolution), one soluble redox mediator (POMs), one membrane (Nafion membrane) and two cells, which potentially increases the cost for the electrolysers. A solid redox mediator, such as Ni(OH)2, has also been successfully used as the relay for decoupled water splitting (Scheme 1c). This kind of design needs no separator between the cathode and the anode; however, an auxiliary relay electrode has been used and the whole cell is still a three-component system, and the overall cost for the electrolyser may not be effectively reduced. Also, among all these designs, since the HER and OER are decoupled in time, there is always an electrode (either the HER or the OER electrode) in an idle state when the cell is in operation. For decoupled water splitting in time, the integration of the HER and OER in one electrode can effectively reduce the cost and space for the electrolyser, which is more practical for scale-up applications; however, a rational design toward this direction has not been proposed.