Despite nearly 40 years of research on CO 2 photocatalytic reduction and the increasing number of works dealing with this application, there are still many unknowns on the mechanistic aspect of the reaction.Perspective pubs.acs.org/JPCL

The activity of NaNbO and NaTaO perovskites for the photocatalytic reduction of CO is studied in this work. For this purpose, sodium niobate and tantalate have been prepared using solid-state reactions, extensively characterised by means of powder X-ray diffraction, UV-vis, photoluminescence and Raman spectroscopies and N adsorption isotherms, and tested in the gas-phase reduction of CO under UV light in a continuous flow photoreactor. NaNbO is constituted of an orthorhombically distorted perovskite structure, while a ca. 4.5 : 1 combination of the orthorhombic and monoclinic modifications is found in the tantalate. Both catalysts exhibit interesting intrinsic activities, with the tantalate material giving rise to a slightly higher performance. This is attributed to a compromise situation between electron-hole recombination and the reducing potential of conduction band electrons. In addition, a decrease in the competition of water protons for photogenerated electrons is observed with both catalysts with respect to TiO.

No abstract

No abstract

Bimetallic Au−Ag/TiO 2 materials have been investigated as promising catalysts for the photocatalytic conversion of CO 2 with water as the reducing agent. The deposition of both metals on the TiO 2 surface was performed using a deposition method in independent steps. Characterization studies reveal a parallel distribution of both metals, with a preferential surface exposure of silver nanoparticles (NPs). The close contact between metal NPs and TiO 2 allows an efficient charge transfer between both phases upon excitation, which results in a distinct reaction mechanism under ultraviolet (UV) and visible illumination. Under UV light, bimetallic catalysts are able to shift the reaction selectivity toward methane, compared to the solely syngas (CO + H 2 ) production over bare TiO 2 . This effect is ascribed to the capacity of the metal NPs to extract photoexcited electrons. Under visible light, this selectivity modification is not observed, whereas bimetallic catalysts are active toward syngas production, significantly improving the residual activity of TiO 2 . Under these conditions, an additional strong interfacial interaction between metal NPs and TiO 2 allows the photoexcitation of electrons from surface states in the band gap, leading to the occurrence of near-surface electron−hole pairs.