Three‐Dimensional GeSe Microstructured Air Brick Photocathode for Advanced Solar Water Splitting

Air brick‐structured GeSe is first synthesized by a rapid box thermal deposition method, and the GeSe thin film with such air brick novel structure demonstrates advanced photoelectrochemical (PEC) performance. It is found that the electrode position of a few CdS nanoparticles (NPs) on a GeSe microair brick (MAB) prior to the chemical bath deposition (CBD) of CdS buffer affects the coverage/passivation efficiency of CdS onto GeSe MAB. In this case, the electrodeposited CdS particles were likely to be the seed for CdS growth/adsorption of Cd 2+ during the subsequent CBD process and also could serve as active sites between the adsorbed layer and buffer layer for collecting electrons and facilitating their transfer, ultimately reducing the recombination loss. The PEC performance, especially the current density, is obviously improved (8 mA cm −2 at 0 V RHE ) compared with that of a device without CdS NPs (3.6 mA cm −2 at 0 V RHE ). Moreover, surface modification with an 80 nm atomic layer deposition TiO 2 protective layer not only slows the photocorrosion of the CdS layer to 5 h but also promotes the half‐cell solar‐to‐hydrogen efficiency to 1.47%. More than 180 μmol H 2 and 90 μmol O 2 are evolved during 3 h of sustained solar light illumination with the final Pt–TiO 2 /CdS/CdS‐NP/GeSe MAB device.