As expected, an increase in the electrolyser's current density was observed under flow conditions, in comparison to that observed under static electrolyte conditions. Interestingly, an increase in the electrolyser's current density was also observed with increasing electrolyte flow rates. The observed increase in the current density, (ΔI) rises rapidly at low flow rates, and then tend to stabilize at a certain plateau at increasing flow rates. To understand the increase in the electrolyser's current density at increasing flow rates, the in-situ visualization of the electrochemical water splitting cell under operation was performed under no-flow and under different flow rate conditions. As a control, the in-situ visualization of an electrolyser cell with 'buffering' electrolyte was performed under no-flow static conditions. As expected, no change in the spatiotemporal fluorescence imaging results was observed upon voltage application in the 'buffered' cell, as the corresponding acid and base by-products formed at the anode and cathode, respectively, are immediately and completely compensated by the externally used buffering agents in this control cell (Figure ). However, in non-buffered neutral medium, a clear spatiotemporal distinction in the fluorescence intensity, at cathode and the anode electrodes, for both 395 nm and 440 nm are observed due to the formation of basic and acidic space regions. To analyse the effect of flow on these acidic and basic conditions, the in-situ fluorescence imaging was performed under static and flow conditions at different flow rates (Figure ). Furthermore, the spatiotemporal ratiometric analysis was performed to visualize any changes occurring upon voltage application, and the concomitant 'neutralization' effect happening upon flowing the electrolyte (Figure ). Interestingly, under a very slow electrolytic flow condition of 3 ml/min (total cell exchange volume factor of 6 exchange/min), a considerable 'shrinking' in the acidic and basic space regions is observed, however, it can be observed that the acidic and basic space fronts are still clearly visible under these flow conditions (Figure ). The ratiometric analysis further demonstrates a clear spatiotemporal pH change upon the application of voltage (static condition, blue colour) in comparison to the non-bias condition (black colour). Upon flowing the electrolyte under a voltage bias, a lesser deviation in the fluorescence intensity ratio (440nm:395nm) is observed (red colour) in comparison to that for without flow (Figure ). Upon increasing the electrolyte flow rate, a systematic decrease in the acidic and basic space fronts is observed, with the nonbias conditions slowly matching the results observed for flow conditions upon voltage bias application. Specifically, at a high flow rate of 29 mL/min (total cell exchange volume factor of 58 exchange/min), no acidic or basic space fronts are visible in the spatiotemporal fluorescence imaging, with the non-bias condition almost perfectly matching with that of bias application at high flow condition in the fluorescence intensity ratio plot (Figure ). Thus, the plot for increase in current density with the increase in flow rates can be directly related to the reduction, or complete inhibition, of the detrimental acidic and basics space fronts forming at the anode and cathode, respectively, upon electrolytic flow during the water splitting process.