All-inorganic CeO2-TiO2 artificial photosynthesis system with forced heterojunctions for methane to C-C coupled products.

Sustainable and efficient photocatalytic conversion of small molecules to liquid fuels/chemicals needs a large extent of charge separation at heterojunctions and equal charge utilization at redox sites. Toward achieving this, visible-light absorbing CeO2 quantum dots (CeQDs) are directly assembled from the precursors (Ce3+ and OH-) into the TiO2 nanopores by the successive ionic layer adsorption and reaction method, and are subsequently integrated structurally and electronically. Assembly of CeQDs into TiO2 leads to a sub-trillion number of heterojunctions in 1 mg photocatalyst material. Concurrent activation of water and methane generates active radicals that help in selective ethanol and a minor amount of acetone formation. Product generation is further enhanced by deliberate reduction of the photocatalyst device, which enhances Ce3+ content and broadens the valence band with a significant change in electronic structure. The detailed analysis of the photocatalyst device and photocatalysis results reveals the charge transfer mechanism and the reaction pathway.