Spinel-Type Mixed Metal Sulfide NiCo2S4 for Efficient Photocatalytic Reduction of CO2 with Visible Light

Mixed metal oxides with a spinel structure have exhibited great opportunities for photocatalytic CO2 reduction; however, the abilities of their sulfide counterparts in this promising area are much less reported. Herein, we demonstrate the synthesis of a ternary metal sulfide, namely NiCo2S4, and its first application to catalyze the CO2 photoreduction reaction under visible light irradiation. The NiCo2S4 material is prepared through a coupled solvothermal-ion exchange strategy, and is fully checked by diverse characterizations, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and N-2 sorption measurements. Under visible light irradiation in a classic tandem photochemical system, this non-noble-metal NiCo2S4 catalyst affords a considerable activity and high stability for CO2 deoxygenative reduction, delivering a high CO-liberating rate of 43.5 mu mol mg(-1) h(-1). The in-situ PL and transient photocurrent measurements reveal that the spinel catalyst can hamper recombination and accelerate transfer of light-excited charge carriers, and thus boosting the CO2 reduction reaction. At last, a possible mechanism of the NiCo2S4-catalyzed CO2 photoreduction reaction is proposed.