Single-cluster Functionalized TiO 2 Nanotube Array for Boosting Water Oxidation and CO 2 Photoreduction to CH 3 OH.

Solar-driven CO 2 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 CH 3 OH and CH 3 CH 2 OH 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 TiO 2 nanotube arrays, resulting in a series of single-cluster functionalized catalysts P 2 M 18 O 62 @TiO 2 and PM 12 O 40 @TiO 2 (M=Mo or W). The single polyoxometalate cluster can be distinctly identified and serves as electronic sponge to accept electrons from excited TiO 2 for enhancing surface-hole concentration and promote water oxidation. Among these samples, P 2 Mo 18 O 62 @TiO 2 -1 exhibits the highest electron consumption rate of 1260 μmol g -1 for CO 2 -to-CH 3 OH conversion with H 2 O as the electron source, which is 11 times higher than that of isolated TiO 2 nanotube arrays. This work supplied a simple synthesis method to realize the single-dispersion of molecular cluster to enrich surface-reaching holes on TiO 2 , thereby facilitating water oxidation and CO 2 reduction.