S-Scheme Co_9S_8@Cd_(0.8)Zn_(0.2)S-DETA Hierarchical Nanocages Bearing Organic CO_2 Activators for Photocatalytic Syngas Production

摘要

Delicate modulations of CO_2 activation and charge carrier separation/migrationare challenging, yet imperative to augment CO_2 photoreduction efficiency.Herein, by supporting diethylenetriamine (DETA)-functionalized Cd_(0.8)Zn_(0.2)Snanowires on the exterior surface of hollow Co9S8 polyhedrons, hierarchicalCo9S8@Cd0.8Zn0.2S-DETA nanocages are fabricated as an S-scheme photocatalystfor reducing CO2 and protons to produce syngas (CO and H_2). The aminegroups strengthen adsorption and activation of CO_2, while the “nanowireon-nanocage” hierarchical hollow heterostructure with an S-scheme interfaceboosts separation and transfer of photoinduced charges. Employing Co(bpy)32+as a cocatalyst, the optimal photocatalyst effectively produces CO and H2 inrates of 70.6 and 18.6 μmol h~(?1) (i.e., 4673 and 1240 μmol g?1 h~(?1)), respectively,affording an apparent quantum efficiency of 9.45 at 420 nm, which is thehighest value under comparable conditions. Ultraviolet photoelectron spectroscopy,Kelvin probe, and electron spin resonance confirm the S-schematiccharge-transfer process in the photocatalyst. The key COOH* species responsiblefor CO_2-to-CO reduction is detected by in-situ diffuse reflectance infraredFourier transform spectroscopy and endorsed by density functional theorycalculations, and thus a possible CO_2 reduction mechanism is proposed.