Ultrahigh Photocatalytic CO2 Reduction Efficiency by Single Metallic Atom Oxide on TiO2

Abstract Photocatalytic carbon dioxide (CO2) reduction is a sustainable and energy-consumption-free route to directly convert the greenhouse gas into chemicals. Given the vast amount of greenhouse gases, numerous efforts have been devoted to developing inorganic photocatalysts due to their stable, low-cost and environmental-friendly properties. However, more efficient titanium dioxide (TiO2) without noble metal or sacrifice/organic agent is highly desirable for CO2 reduction practical application, and it is also difficult and urgently in demand for TiO2 producing selectively valuable compounds, i.e. industrial chemicals and fuels. Here, we develop a novel “adatom at step” strategy via anchoring single tungsten atom oxide (STAO) site on intrinsic steps of classic TiO2 nanoparticles. The composition of single-sites can be controlled by tuning the ratio of adatom W5+ to neighboring Ti3+, resulting in significant CO2 reduction efficiency and selectively yield of carbon monoxide (CO) or methane (CH4) as main products. The W5+-dominated catalysts can achieve an ultrahigh photocatalytic CH4 production of 59.3 μmol/g/h, while the Ti3+-dominated catalysts can achieve a CO production of 181.4 μmol/g/h, which both exceed those of pristine TiO2 by more than one order of magnitude. The mechanism relies on the accurate control of atomic sites with high coverage and the subsequent excellent electron-hole separation along with favorable adsorption-desorption of intermediates on sites. This approach not only provides a novel strategy for inorganic catalytic single-sites with superior performance, but also identifies the rational design mechanisms of the efficient site with controllable production.