Metal

Catalysis

Adsorption

Engineering

Chemical physics

Nanoparticle

Photochemistry

Metallurgy

Materials science

Nuclear physics

Transition metal

Biochemistry

Decomposition

Inorganic chemistry

Chemical engineering

Physical chemistry

Redox

Physics

Nanotechnology

Organic chemistry

Irradiation

Mathematics

Desorption

Geometry

Chemistry

Selectivity

Photocatalysis

Reduction (mathematics)

Nature Communications

Achieving CO2 reduction with H2O on metal photocatalysts and understanding the corresponding mechanisms at the molecular level are challenging. Herein, we report that quantum-sized Au nanoparticles can photocatalytically reduce CO2 to CO with the help of H2O by electron-hole pairs mainly originating from interband transitions. Notably, the Au photocatalyst shows a CO production rate of 4.73 mmol g-1 h-1 (~100% selectivity), ~2.5 times the rate during CO2 reduction with H2 under the same experimental conditions, under low-intensity irradiation at 420 nm. Theoretical and experimental studies reveal that the increased activity is induced by surface Au-O species formed from H2O decomposition, which synchronously optimizes the rate-determining steps in the CO2 reduction and H2O oxidation reactions, lowers the energy barriers for the *CO desorption and *OOH formation, and facilitates CO and O2 production. Our findings provide an in-depth mechanistic understanding for designing active metal photocatalysts for efficient CO2 reduction with H2O.

Molecular-level insight into photocatalytic CO2 reduction with H2O over Au nanoparticles by interband transitions