Comprehensive-designed graphene-based quaternary nanocomposite and its synergistic effect towards photoelectrocatalytic CO2 reduction under different electrolytes.

• The development of a photoelectrocatalytic reactor for the CO 2 reduction to hydrocarbon fuels. • Development of a new catalytic quaternary CuO-Graphene-ZnFe 2 O 4 -TiO 2 nanocomposite. • The different types of electrolytes in CO 2 ER reaction to support the interaction between the cathode surface and the outcoming final product. • A highest FE in each tests, especially 44.08 % in buffer electrolyte with UV-light. • The pH of the electrolyte and the proton existence impact on the FE (%) values. Research on the electrochemical reduction of CO 2 (CO 2 ER) and photoelectrochemical reduction of CO 2 (PEC-CO 2 R) to produce hydrocarbon fuels using renewable energy sources is gaining significant attention. In this study, we developed a new quaternary-structured catalytic material that has garnered interest in the catalysis industry. The performance of the catalysts was assessed by conducting CO 2 reduction tests using different electrolytes to support the interaction between the cathode surface and the final product. The selectivity and activity of the nanocomposites were evaluated based on the Faradaic efficiency (FE). Among all the tested nanocomposites, the CuO-Graphene-ZnFe 2 O 4 -TiO 2 nanocomposites (CGZFOT NCs) exhibited the highest FE in each test, particularly 44.08 % in the buffer electrolyte with UV light, which facilitated electron transfer for CO 2 reduction to methanol. The second highest FE value of 42.2 % was achieved when NaHCO 3 was used as the electrolyte under UV light. Notably, both the experimental conditions demonstrated high FE values in the absence of a light source. Furthermore, the presence of protons affects FE (%) values. NaHCO 3 , for instance, dissociates into Na+ and HCO 3 –, and acts as a carrier for hydrocarbon ions, enhancing absorption. The buffering capacity of the buffer electrolyte actively reacts with the produced hydroxide, promoting the mass transfer of CO 2 gas. This results in a high current density for redox reactions in sodium hydrocarbonate and a buffer electrolyte for all working electrodes (WEs). The choice of electrolyte significantly affects the performance of the catalyst; thus, we compared catalysts using only one electrolyte to determine whether their activity and selectivity are related to the catalyst structure and properties. The Z-scheme charge carrier mechanism of the quaternary CGZFOT NCs offered efficient separation and carrier of electron-hole pairs, and it was also found that the close-parallel interfacial connection led to improved photoelectrochemical CO 2 reduction (PEC-CO 2 R). In addition, we believe that our experiments provide a complete picture of the performance of catalysts in different environments. [ABSTRACT FROM AUTHOR]