Strontium Titanate Based Artificial Leaf Loaded with Reduction and Oxidation Cocatalysts for Selective CO₂ Reduction Using Water as an Electron Donor

Thin film of SrTiO₃ nanorods loaded with reduction and oxidation cocatalysts drove the selective reduction of carbon dioxide (CO₂) into carbon monoxide (CO), as well as caused the production of equivalent oxygen molecules through water oxidation under UV irradiation. The described film functioned as a free-standing plate without any bias potential application, similar to a natural leaf. The film was facilely fabricated by a simple hydrothermal and annealing treatment of a titanium substrate to produce the SrTiO₃ nanorod film (STO film) followed by two steps of loading the reduction and oxidation cocatalysts onto the surface of the STO. As a reduction cocatalyst, a Cu_xO nanocluster was chosen to achieve selective reduction of CO₂ into CO, whereas a cobalt- and phosphate-based cocatalyst (CoPi) facilitated oxidation on the STO surface to promote oxygen generation. For the photocatalysis test, a wireless film was simply set into an aqueous solution bubbled with CO₂ in a reactor, and CO production was observed in the headspace of the reactor under UV irradiation. Compared to the bare STO film, the dual cocatalyst-loaded STO film exhibited 2.5 times higher CO generation. H₂ production was very limited in our system, and the amount of molecules generated by the reduction reaction was almost twice that of the generated oxygen molecules, proving that water molecules acted as electron donors. Our artificial leaf consists of abundant and nontoxic natural elements and represents the first achievement of stoichiometric CO₂ reduction using water as an electron donor by a free-standing natural leaflike plate form.