Designed Synthesis of Cu₂O Quantum Dots/TiO₂ Nanotubes Heterostructure as a Photocatalyst for Converting CO₂ to CH₄

Herein, H⁺ in oxalic acid is used instead of Na⁺ to obtain titanate nanosheets through P200 hydrolysis, which further curls to form a multilayer TiO₂ nanotubes (NTs) structure. Then, Cu₂O quantum dots (QDs) are successfully loaded on TiO₂ NTs via a hydrothermal method using fructose as a reducing agent. The optical, impedance, and photocurrent tests indicate that the composite structure improves its optoelectronic performance. The photocatalytic H₂ production and CO₂ reduction efficiency of Cu₂O QDs/TiO₂ NTs are lower than those of TiO₂ NTs. However, the molar ratio of CH₄ to CO produced by CO₂ reduction of Cu₂O QDs/TiO₂ NTs composite catalyst is greater than that of pure TiO₂ NTs. The CH₄ production accounts for 97%, indicating that the composite catalyst has a high CH₄ selectivity. The experimental and density functional theory calculation results prove that the Z‐scheme heterojunction accelerates the separation and transfer of photogenerated carriers, and broadens the absorption range of visible light.