Mechanistic study of DETA-modified CdS for carbon dioxide reduction†

Cadmium sulfide (CdS) exhibits remarkable light absorption capabilities and is widely employed in photocatalytic reduction of CO₂. Nevertheless, the crystal facet effects on the micro-scale mechanisms governing CO₂ conversion on CdS remain elusive. This study theoretically investigates the electronic properties of hexagonal-phase (101), (001), and cubic-phase (111) CdS surfaces modified with diethylenetriamine (DETA). From a microscopic viewpoint, it elucidates the unique bonding characteristics of CO₂ on different exposed facets of DETA/CdS and the formation mechanisms leading to products such as CO, HCOOH, CH₂O, CH₃OH, and CH₄. Our findings reveal that the DETA/CdS(101) surface is the most stable, effectively adsorbing hydrogen and CO₂ at varied Cd sites with a high selectivity towards CO production, thereby showing promise for syngas generation, albeit with potential yields of formic acid and methane. Conversely, DETA/CdS(001) and (111) primarily facilitate the reduction of CO₂ to CH₄. These discoveries offer theoretical insights into photochemical experiments involving CO₂ reduction on CdS, shedding light on the influence of crystal facets on reaction pathways.