Facet‐Dependent Co3O4 Nanocrystals for Efficient and Highly Selective Photothermal CO2 Hydrogenation

Abstract Photothermal CO 2 hydrogenation with green H 2 for conversion into fuels or chemicals is a promising technology for efficient CO 2 conversion with low energy input. However, low catalytic activity and selectivity are one of the difficulties in photothermal catalysis, so it is crucial to develop photothermal catalysts with high catalytic activity. By employing crystalline surface engineering, specific highly active crystalline surfaces can be exposed, which have more active sites and can improve the photothermal performance of the catalysts to some extent. Based on this, two kinds of Co 3 O 4 nanocrystals with exposed different facets are synthesized via the hydrothermal method, and the facet‐dependent reactivity in photothermal CO 2 hydrogenation is explored. The results showed that the Co 3 O 4 nanocubes with exposed (001) facets presented the CH 4 yield of 11.00 mmol h −1 with 61.06% CO 2 conversion and 80% CH 4 selectivity, which is ≈39% higher than the yield of Co 3 O 4 octahedrons enclosed by (111) facets. Co 3 O 4 with exposing only (001) facets has a higher Co 2+ /Co 0 ratio, thus resulting in better CO 2 adsorptions favoring the formic acid path to produce methane. This study provides a series of new facet‐dependent photothermal catalyst designs and reveals for the first time the effect of thermal energy on catalyst conductivity.