Reuse of TiO₂ from Waste SCR Catalyst to Synthesis g-C₃N₄/TiO₂ for Photocatalytic CO₂ Reduction

Photocatalytic reduction of CO₂ to CO offers a promising solution for generating renewable energy and combating global warming. By combining graphitic carbon nitride (g-C₃N₄) with recovered TiO₂ from waste Selective Catalytic Reduction (SCR) catalysts, the g-C₃N₄/TiO₂ heterostructure photocatalyst with excellent performance in CO₂ reduction was developed. This approach not only ensures cost-effectiveness but also promotes the recycling of waste SCR catalysts, which is highly significant. The TiO₂ extracted from waste SCR catalysts through carbonate leaching was utilized to prepare a series of g-C₃N₄/TiO₂ heterojunction photocatalyst via a calcination process. The photocatalytic efficacy of these g-C₃N₄/TiO₂ photocatalysts was assessed in CO₂ reduction. The recovered TiO₂ retained the crystal structure of standard anatase TiO₂ phase, as confirmed by XRD analysis. The g-C₃N₄/TiO₂ heterojunction photocatalyst, featuring a tremella-like structure with a larger specific surface area and a narrower band gap, demonstrated excellent photocatalytic performance. For instance, the specific surface area and band gap of the CNT3:1 sample were found to be 109 m²g⁻¹ and 2.56 eV, respectively, with an average CO yield of 1.2488 μmol·g⁻¹ h⁻¹. In this study, we hope to shed new light on the reutilization of waste SCR catalysts’ TiO₂ carrier and the design of efficient photocatalysts with significant economic benefits by producing sustainable g-C₃N₄/TiO₂ photocatalyst materials with recovered titanium components from waste SCR catalysts for photocatalytic CO₂ reduction.