Nanochannel-Induced Efficient Water Splitting at the Superhydrophobic Interface.

Constructing a favorable reaction configuration at the water/catalyst interface is crucial for high-efficiency semiconductor-based water splitting. For a long time, a hydrophilic surface of semiconductor catalysts has been considered necessary for efficient mass transfer and adequate contact with water. In this work, by constructing a superhydrophobic PDMS-Ti/TiO interface (denoted P-TTO) with nanochannels arranged by nonpolar silane chains, we observe overall water splitting efficiencies improved by an order of magnitude under both the white light and simulated AM1.5G solar irradiation compared to the hydrophilic Ti/TiO interface. The electrochemical overall water splitting potential on the P-TTO electrode also decreased from 1.62 to 1.27 V, which is close to the thermodynamic limit of 1.23 V. Through the diffuse reflection infrared Fourier transform spectroscopy, a nanochannel-induced water configuration transition is directly detected. The density functional theory calculation further verifies the lower reaction energy of water decomposition at the water/PDMS-TiO interface. Our work achieves efficient overall water splitting through nanochannel-induced water configurations without changing the bulk of semiconductor catalyst, which reveals the significant role of water status at the interface in the efficiency of the water splitting reaction over the properties of catalyst materials.