Solar photoelectrochemical water-splitting is a potential process for producing renewable hydrogen. Here, the energy transport phenomena associated with hydrogen bubble generation are investigated for the future design of large-scale reactors. Light transfer analysis shows that using a thin aqueous-electrolyte layer is essential for utilizing the full spectrum of solar radiation. The hydrogen bubble flow needs to be redirected to avoid screening the photoelectrode from incident light. Hence, a bubble flow guide for controlling the stream of bubbles in a planarly confined aqueous electrolyte has been proposed. It is found that the surface wettability and inclination angle are important for designing an effective bubble flow guide. The hydrophilic coating on a polymethyl methacrylate surface inhibits bubble adhesion and reduces energy loss. Furthermore, measuring the electrode potential variation during water electrolysis is useful for comparing the performances of bubble flow guides.