S‐Scheme Co9S8@Cd0.8Zn0.2S‐DETA Hierarchical Nanocages Bearing Organic CO2 Activators for Photocatalytic Syngas Production

Abstract Delicate modulations of CO2 activation and charge carrier separation/migration are challenging, yet imperative to augment CO2 photoreduction efficiency. Herein, by supporting diethylenetriamine (DETA)‐functionalized Cd0.8Zn0.2S nanowires on the exterior surface of hollow Co9S8 polyhedrons, hierarchical Co9S8@Cd0.8Zn0.2S‐DETA nanocages are fabricated as an S‐scheme photocatalyst for reducing CO2 and protons to produce syngas (CO and H2). The amine groups strengthen adsorption and activation of CO2, while the “nanowire‐on‐nanocage” hierarchical hollow heterostructure with an S‐scheme interface boosts separation and transfer of photoinduced charges. Employing Co(bpy)32+ as a cocatalyst, the optimal photocatalyst effectively produces CO and H2 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 CO2‐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 CO2 reduction mechanism is proposed.