Single-cluster Functionalized TiO2 Nanotube Array for Boosting Water Oxidation and CO2 Photoreduction to CH3OH.

Abstract

Solar-driven CO2 reduction and water oxidation to liquid fuels represents a promising solution to alleviate energy crisis and climate issue, but it remains a great challenge for generating CH3OH and CH3CH2OH dominated by multi-electron transfer. Single-cluster catalysts with super electron acceptance, accurate molecular structure, customizable electronic structure and multiple adsorption sites, have led to greater potential in catalyzing various challenging reactions. However, accurately controlling the number and arrangement of clusters on functional supports still faces great challenge. Herein, we develop a facile electrosynthesis method to uniformly disperse Wells-Dawson- and Keggin-type polyoxometalates on TiO2 nanotube arrays, resulting in a series of single-cluster functionalized catalysts P2M18O62@TiO2 and PM12O40@TiO2 (M = Mo or W). The single polyoxometalate cluster can be distinctly identified and serves as electronic sponge to accept electrons from excited TiO2 for enhancing surface-hole concentration and promote water oxidation. Among these samples, P2Mo18O62@TiO2-1 exhibits the highest electron consumption rate of 1260 µmol g-1 for CO2-to-CH3OH conversion with H2O as the electron source, which is 11 times higher than that of isolated TiO2 nanotube arrays. This work supplied a simple synthesis method to realize the single-dispersion of molecular cluster to enrich surface-reaching holes on TiO2, thereby facilitating water oxidation and CO2 reduction.