Enhancement of photocatalytic reduction of CO2 to CH4 over TiO2 nanosheets by modifying with sulfuric acid

- TiO2 nanosheets with exposed {0 0 1} facets was modified with sulfuric acid.
- Effective photocatalytic activity for CO2 reduction to CH4 under visible light.
- Acidification promotes the formation of oxygen vacancies/Ti3+ species.
- Surface protonation extends the lifetime of photogenerated electron-hole pairs.