Constructing solid waste-derived carbon fiber with self-doped Ti³⁺/TiO₂ (SWCFs/Ti³⁺/TiO₂) heterojunction for photocatalytic CO₂ reduction

Solid waste carbon fiber-reinforced polymers (CFRPs) consist of carbon fibers embedded within a polymer matrix that can be converted to low-cost carbon fibers as a cocatalyst. In this work, CFRPs solid waste-derived carbon fibers (SWCFs) assembled with TiO₂ to construct SWCFs/Ti³⁺-mediated TiO₂ composite. The CF-supported Ti³⁺/TiO₂, due to higher light absorbance efficiency and efficient charge separation capacity, examined and tested for CO₂ photoreduction. The optimized 10% SWCFs/Ti³⁺/TiO₂ was able to produce CO and CH₄ of 19.13 and 3.40 µmol g⁻¹ h⁻¹ in a continuous flow photoreactor system. Compared to using only TiO₂, the photoactivity for CO and CH₄ generation over the composite was 15.01 and 2.88 times higher. Charge recombination over the TiO₂ surface was inhibited, and visible light absorbance was increased by the synergistic impact of SWCFs with surface defects (Ti³⁺). The stability test was further conducted and confirmed continuous production of CO and CH₄ in multiple cycles without obvious deactivation. Thus, constructing SWCFs cocatalysts with surface defectives Ti³⁺/TiO₂ was beneficial to maximize photocatalytic efficiency for CO₂ reduction and would be useful for other energy applications.