S‐Scheme Co<sub>9</sub>S<sub>8</sub>@Cd<sub>0.8</sub>Zn<sub>0.2</sub>S‐DETA Hierarchical Nanocages Bearing Organic CO<sub>2</sub> Activators for Photocatalytic Syngas Production
Bo Su, Mei Zheng, Wei Lin, Xue Feng Lu, Deyan Luan, Sibo Wang, Xiong Wen Lou
Abstract
Abstract Delicate modulations of CO 2 activation and charge carrier separation/migration are challenging, yet imperative to augment CO 2 photoreduction efficiency. Herein, by supporting diethylenetriamine (DETA)‐functionalized Cd 0.8 Zn 0.2 S nanowires on the exterior surface of hollow Co 9 S 8 polyhedrons, hierarchical Co 9 S 8 @Cd 0.8 Zn 0.2 S‐DETA nanocages are fabricated as an S‐scheme photocatalyst for reducing CO 2 and protons to produce syngas (CO and H 2 ). The amine groups strengthen adsorption and activation of CO 2 , while the “nanowire‐on‐nanocage” hierarchical hollow heterostructure with an S‐scheme interface boosts separation and transfer of photoinduced charges. Employing Co(bpy) 3 2+ as a cocatalyst, the optimal photocatalyst effectively produces CO and H 2 in rates 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 the highest value under comparable conditions. Ultraviolet photoelectron spectroscopy, Kelvin probe, and electron spin resonance confirm the S‐schematic charge‐transfer process in the photocatalyst. The key COOH * species responsible for CO 2 ‐to‐CO reduction is detected by in‐situ diffuse reflectance infrared Fourier transform spectroscopy and endorsed by density functional theory calculations, and thus a possible CO 2 reduction mechanism is proposed.