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A facile heterogeneous photocatalyst system that consists of a nickel complex and cadmium sulfide (CdS), which act as the catalyst and light antenna, respectively, was developed to the efficiency photocatalytic activation and conversion of CO2. Ni(bpy)3Cl2 was firstly found to be an active material for photocatalytic CO2 reduction. Besides, promoting the photo-generated electrons transfer from CdS to CO2 through such nickel complex further enhanced the catalytic activity. 5.2 µmol of CO has been obtained in acetonitrile solution containing Ni(bpy)3Cl2 under 2 h visible-light irradiation, which is approximately sixfold more than that system without Ni(bpy)3Cl2 complex. The different amount of Ni(bpy)3Cl2 used reveals the relationship of active center and photocatalytic performance. The use of a suitable amount of Ni(bpy)3Cl2 resulting in an apparent quantum yield of 1.68% at 420 nm. Electrochemical measurement and photochemical observation suggest a possible mechanistic detail of charge carrier transfer and information of key intermediates during CO2 reduction, which broadens the perspective of reaction mechanism.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Conversion of CO 2 into value-added chemicals by solar energy is one of the most promising pathways to partially address both energy crisis and global warming effect. The properties of reaction medium play a key role in determining the efficiency of CO 2 photoreduction and modulating the distribution of reaction products. Herein, we report the detailed investigation of solvent effects on the performance of photocatalytic CO 2 reduction by means of photo-/electro-chemical and spectroscopy techniques. The relationship between photochemical CO 2 performance and solvent properties (e.g., viscosity, solubility, and electrochemical behaviors) are systematically explored. The active intermediates for CO 2 photoreduction catalysis are examined by UV–vis absorption spectra. Moreover, a possible reaction pathway involving photoexcited charge transfers and intermediate species transformations in various solvents is proposed. [ABSTRACT FROM AUTHOR]