Photocatalytic Conversion of Formic Acid to Syngas (CO + H₂) and Methane with Homogeneous Molecular Cobaloxime Catalysts

The catalytic conversion of formic acid is a promising method for accessing clean fuels. H2 and CO, as products of the conversion process, have been extensively researched, but other direct conversion processes remain to be developed. Herein, for the first time, we report the use of homogeneous molecular cobaloxime catalysts combined with CdS nanorods (NRs) as a highly efficient photocatalytic system to produce syngas with CH4 from HCOOH. As a result, the highest rate of CH4 production reached 80.5 μmol g–1 h–1, with H2 and CO evolution rates of 60.5 and 24 mmol g–1 h–1, respectively. Moreover, the use of cobaloxime catalysts also markedly enhanced the long-term stability of the resulting material for gas evolution. The superior performance for CH4 and syngas evolution can be attributed to the promoted charge transfer and separation in the homogeneous molecular cobaloxime systems. This work provides new insights into the photocatalytic conversion of formic acid to other clean fuels.