One Dimensional CdS Nanotube vs CdS Bulk Structure for Photocatalytic Water Splitting: Role of Dimensionality

摘要： Using the state-of-the-art density functional theoretical calculations, we have modelled a facetted CdS nanotube (NT) catalyst for photocatalytic water splitting. The overall photocatalytic activity of the CdS photocatalyst has been predicted based on the electronic structures, band edge alignment, and overpotential study. For comparisons, we have also investigated the water spilitting process over the CdS bulk structure. The band edge alignment along with oxygen evolution reaction/hydrogen evolution reaction (OER/HER) mechanism studies help us to find out the effective overpotential for the overall water splitting on these surfaces. Our study shows that CdS NT has highly stabilized valence band edge compared to that in the CdS bulk due to strong p-d mixing. Such highly stabilized valence band edge is important for the hole-transfer process and reduces the risk of electron-hole recombination. Such nanotube requires less overpotential for water oxidation reaction than the periodic CdS. All these suggest that the efficiency of water oxidation/reduction process further improves in CdS as we reduce its dimensionality. More importantly, we report here that there are two factors, which makes CdS nanotube as a better photocatalyst material compared to its bulk counterpart. Furthermore, the stabilized valence band edge is good for their photostability too as bulk CdS suffers from photostability.