▎ 摘　　要

Nano-sized catalysts have been widely studied for CO2 reduction to hydrocarbon fuels. Herein, we study the new-modeled ternary nanocomposite that can use in photocatalytic and electrochemical CO2 reduction. In order to adjust the energy of the catalyst band and the characteristics of the effective charge carrier, we firstly synthesized the AgFeNi2S4 quaternary nanocomposite and then used it to model the ternary nanocomposites, and all the nanocomposites were synthesized using the Pechini method. The activity of the nanocomposites is directly related to the output of methanol productions. The highest methanol yields were found after 48 h of irradiation under the UV light, and the yields were 8.679%, 6.349%, and 4.136%. The methanol yields were less, such as 6.291%, 4.738%, and 2.339%, after 48 h of Visible-light irradiation. The stability and reusability of the catalysts are the main factors that can define the sturdiness of a photocatalyst in practical applications. The sturdiness of the catalyst has been tested four times by recycling tests, and as a result, the yield of the final product (methanol) has not decreased, confirming the stability of the catalyst The methanol reaction rate and Faraday efficiency value were calculated on all working electrodes. The Faraday efficiency of the AgFeNi2S4-Graphene-TiO2 ternary nanocomposite was 44.25%; this is an increase in the value of the Faraday efficiency, which proves that the design of the new nanocomposite successfully increases the activity of the working electrode and has a positive effect on the electrochemical reduction of CO2. The photocatalytic and electrochemical CO2 reduction data show that the preparation method, morphological state, and charge carrier properties of the photocatalyst are important for the catalytic activity and efficiency of the methanol evolution pathway.