Photothermal hydrocarbon synthesis using alumina-supported cobalt metal nanoparticle catalysts derived from layered-double-hydroxide nanosheets

The photothermal conversion of syngas (CO and H-2) offers a relatively straightforward method for the production of solar fuels with high solar-to-fuel conversion efficiencies. Herein, we report the successful synthesis of a series of novel Co-based catalysts via hydrogen reduction of CoAl layered-double-hydroxide (LDH) nanosheets at temperatures(x) in the range 300-700 degrees C. With increasing reduction temperature, the selectivity of the Co-x catalysts for photothermal CO hydrogenation under UV-vis irradiation shifted progressively from CH4 to high-value hydrocarbons, with the Co-700 catalyst affording a remarkable C2+ selectivity of 65% (similar to 36.3% C2-4 vs similar to 28.7% C5+) at a CO conversion of 35.4%. High-resolution transmission electron microscopy, X-ray diffraction and Co K-edge extended X-ray absorption fine structure analyses revealed the Co-700 catalyst contained metallic Co nanoparticles supported by amorphous alumina, whilst density functional theory calculations revealed that metallic Co nanoparticle formation improved the C-C coupling ability of the LDH-derived catalysts, thus enhancing the selectivity to higher hydrocarbons. This study further highlights the great promise of photothermal catalytic systems for CO conversion to fuels and other valuable chemicals feedstocks.