Efficient and economically affordable TiO₂ nanotube-based ternary photocatalysts for CO₂ conversion boosted by NiO nanoparticles and carbon quantum dots

Photocatalytic CO₂ conversion, in general, requires the incorporation of expensive and noble materials to achieve a highly efficient conversion rate. Herein, the TNT/NiO/CQD ternary nanocomposites without any expensive materials and material modification are fabricated for the demonstration of efficient and economically affordable photocatalytic CO₂ conversion, to our best knowledge, for the first time. The TNT-based ternary photocatalysts are successfully prepared by a simple anodization and immersion process. The TNT/NiO/CQD ternary nanocomposites produce 1.47 μmol·cm⁻²·h⁻¹ (≈c.a. 2834 μmol·g⁻¹·h⁻¹) of CH₄ as the sole product under AM 1.5 illumination. This is five times higher performance than that of bare TNT and the performance is comparable to that of any other TiO₂-based unitary, binary, or ternary photocatalysts. This highly enhanced performance results from effective junction formation between TNT and NiO NP, and the dual role of CQDs as a light absorber and charge transporter/collector in the system. The formation of Z-scheme at the TNT/NiO interface leads to efficient charge transfer via a TiO₂/NiO bond. The light absorption of the photocatalysts is enhanced and extended by decorated CQDs due to their small band gap. The charge transfer and collection are further improved by charge depletion at the TNT/CQD interface and the charge transfer at the NiO/CQD interface. This work provides a possible model for the realization of efficient and economically affordable photocatalytic CO₂ conversion.