Cocatalysts engineering promotes photocatalytic CO2 reduction of hollow TiO2 nanospheres: From Cu nanoparticles to CuAg species

Hollow-structured TiO₂ is promising for photocatalytic CO₂ reduction due to its high surface area and light absorption. This study aims to enhance its photocatalytic activity through the engineering of Cu and CuAg alloy cocatalysts. Hollow TiO₂ was synthesized by a hard template method, followed by Cu loading and CuAg alloy formation via a chemical replacement reaction. The optimal 7% Cu loading achieved the highest CH₄ yield of 2.47 μmol g^-1 h^-1 among the TiO₂-Cu composites. Introducing Ag further enhanced the performance, with the Cu:Ag= 9:1 alloy boosting the CH₄ yield to 6.72 μmol g^-1 h^-1, approximately 14 times that of pure TiO₂. Characterization techniques such as XRD, SEM, and XPS were also employed to analyze the phase composition, microstructure, and photoelectrochemical properties of the synthesized materials. The experimental findings indicate that the introduction of the CuAg alloy significantly promotes charge separation and transfer efficiency, and increases the effective active sites on the TiO₂ surface, thereby greatly enhancing the efficiency of the photocatalytic reaction. These findings offer insights into the design of efficient photocatalytic materials for sustainable energy applications.