Epitaxially grown silicon-based single-atom catalyst for visible-light-driven syngas production

Abstract

Improving the dispersion of active sites simultaneous with the efficient harvest of photons is a key priority for photocatalysis. Crystalline silicon is abundant on Earth and has a suitable bandgap. However, silicon-based photocatalysts combined with metal elements has proved challenging due to silicon's rigid crystal structure and high formation energy. Here we report a solid-state chemistry that produces crystalline silicon with well-dispersed Co atoms. Isolated Co sites in silicon are obtained through the in-situ formation of CoSi₂ intermediate nanodomains that function as seeds, leading to the production of Co-incorporating silicon nanocrystals at the CoSi₂/Si epitaxial interface. As a result, cobalt-on-silicon single-atom catalysts achieve an external quantum efficiency of 10% for CO₂-to-syngas conversion, with CO and H₂ yields of 4.7 mol g_(Co)^-1 and 4.4 mol g_(Co)^-1, respectively. Moreover, the H₂/CO ratio is tunable between 0.8 and 2. This photocatalyst also achieves a corresponding turnover number of 2 × 10⁴ for visible-light-driven CO₂ reduction over 6 h, which is over ten times higher than previously reported single-atom photocatalysts.