Controllable synthesis of CuPc/N-rich doped (0 0 1) TiO2 S-scheme nanosheet heterojunctions for efficiently wide-visible light-driven CO2 reduction

Abstract

Inspired by natural photosynthesis, the rational design of efficient S-scheme heterojunctions holds promises for CO2 conversion by utilizing solar light. Herein, nitrogen-rich doped 001-exposed anatase nanosheets (NPT) have been designed and fabricated by post-treatment with NH3 at a high temperature of 600 °C to phosphate modified TiO2 firstly, and then controllably coupled with copper phthalocyanine (CuPc) via a hydroxyl-induced assembly process to construct a wide-visible-light responsive heterojunction towards CO2 conversion. The optimized CuPc/NPT heterojunction achieves a high production rate of CO (∼5 μmol/g/h) under visible light irradiation, with ∼9-fold enhancement compared with generally N-doped TiO2. Based on the experimental results mainly from photocurrent action spectra, electron paramagnetic resonance measurements, electrochemical reduction curves and in-situ diffuse reflectance infrared Fourier transform spectra, it is confirmed that the exceptional photoactivity is attributed to the N-rich doping for increasing visible-light absorption of TiO2, the effective S-scheme charge transfer from the closely-contacted CuPc/NPT heterojunction with wide visible-light absorption, and subsequently to the electron transfer from the Pc ligand to central metal Cu2+ with good catalytic function for CO2 reduction. This work provides feasible routes for the design and preparation of TiO2-based photocatalysts for solar-driven CO2 conversion.