Insights into the role of MgAl layered double oxides interlayer in Pt/TiO2 toward photocatalytic CO2 reduction

Abstract The representative TiO 2 loaded with cocatalyst (e.g., Pt) have been used extensively for the photocatalytic CO 2 reduction in solar-to-chemical energy conversion. However, it still suffers from low efficiency, due to the weak adsorption/activation of CO 2 . In this work, an MgAl layered double oxides (MgAl-LDO) was successfully introduced into the interface of Pt/TiO 2 , by in-situ deposition of MgAl layered double hydroxides and subsequent high temperature calcination. The structure, optical property and the photocatalytic activity for CO 2 reduction of as-fabricated Pt/MgAl-LDO/TiO 2 were experimentally investigated. Especially, the roles of MgAl-LDO during the CO 2 reduction process were highlighted. It concluded MgAl-LDO possessed Lewis acidic and Lewis basic bifunctional roles that enhanced the performance of the photocatalytic CO 2 reduction. The optimal yields of CO and CH 4 of Pt/MgAl-LDO/TiO 2 exhibited ca. 2 and 11 times as high as that of Pt/TiO 2 , respectively. The adsorption states of CO 2 and the adsorbed species in the course of photoreduction of CO 2 with H 2 O vapor on Pt/MgAl-LDO/TiO 2 were examined by in-situ infrared spectroscopy. Monodentate carbonate (m-CO 3 2− ) and monodentate bicarbonate (m-HCO 3 − ) were found to be the main surface species that adsorbed. In the presence of H 2 O, m-CO 3 2− species could be readily converted to active m-HCO 3 − intermediate, which was subsequently transformed into surface CO 2 − . This was attributed to the fact that MgAl-LDO contains much more strong Lewis basic sits for CO 2 adsorption to produce m-CO 3 2− and the Lewis acid sites for the dissociation of H 2 O into H + and OH groups. Moreover, photoluminescence spectra further indicated that oxygen vacancy existed in the interface of MgAl-LDO/TiO 2 , which facilitated the photogenerated charges separation and also contributed to the enhanced photocatalytic performance. As a result, the Lewis acidic-basic characteristics of MgAl-LDO, as well as the improved charges separation, should be responsible for the increased photocatalytic activity of Pt/MgAl-LDO/TiO 2 toward CO 2 reduction.