Nanoscale capillarity for mitigating gas bubble adhesion on arrayed photoelectrode during photoelectrochemical water splitting

One-dimensional (1D) arrayed photoelectrodes usually present superior performance in photoelectrochemical (PEC) water splitting. This superiority is known to be attributed to directional transport of photogenerated charge carriers. Herein, we show that in addition to this intrinsic charge transport property, a 1D arrayed structure introduces nanoscale capillary wetting, which is also believed to contribute to the improved PEC performance. Our theoretical model predicts that this morphology-dependent capillarity leads to the formation of a liquid film between the photoelectrode surface and the adhered bubble (the generated H-2/O-2 bubble), thus largely reducing the blockage of active sites at the bubble base. This prediction has been experimentally demonstrated by taking arrayed TiO2 nanorods as a model photoelectrode, with the observation of the PEC activity within the bubble base. This work extends our knowledge toward hydrodynamic functionality involved in morphology-controlled photoelectrodes for enhanced PEC performance.