Molecular oxygen enhances H<sub>2</sub>O<sub>2</sub> utilization for the photocatalytic conversion of methane to liquid-phase oxygenates.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 36335138.
- Also identified by DOI 10.1038/s41467-022-34563-4 and PMC identifier 9637122.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
H<sub>2</sub>O<sub>2</sub> is widely used as an oxidant for photocatalytic methane conversion to value-added chemicals over oxide-based photocatalysts under mild conditions, but suffers from low utilization efficiencies. Herein, we report that O<sub>2</sub> is an efficient molecular additive to enhance the utilization efficiency of H<sub>2</sub>O<sub>2</sub> by suppressing H<sub>2</sub>O<sub>2</sub> adsorption on oxides and consequent photogenerated holes-mediated H<sub>2</sub>O<sub>2</sub> dissociation into O<sub>2</sub>. In photocatalytic methane conversion over an anatase TiO<sub>2</sub> nanocrystals predominantly enclosed by the {001} facets (denoted as TiO<sub>2</sub>{001})-C<sub>3</sub>N<sub>4</sub> composite photocatalyst at room temperature and ambient pressure, O<sub>2</sub> additive significantly enhances the utilization efficiency of H<sub>2</sub>O<sub>2</sub> up to 93.3%, giving formic acid and liquid-phase oxygenates selectivities respectively of 69.8% and 97% and a formic acid yield of 486 μmol<sub>HCOOH</sub>·g<sub>catalyst</sub><sup>-1</sup>·h<sup>-1</sup>. Efficient charge separation within TiO<sub>2</sub>{001}-C<sub>3</sub>N<sub>4</sub> heterojunctions, photogenerated holes-mediated activation of CH<sub>4</sub> into ·CH<sub>3</sub> radicals on TiO<sub>2</sub>{001} and photogenerated electrons-mediated activation of H<sub>2</sub>O<sub>2</sub> into ·OOH radicals on C<sub>3</sub>N<sub>4</sub>, and preferential dissociative adsorption of methanol on TiO<sub>2</sub>{001} are responsible for the active and selective photocatalytic conversion of methane to formic acid over TiO<sub>2</sub>{001}-C<sub>3</sub>N<sub>4</sub> composite photocatalyst.