Integration of Nitrogen-Doped Amorphous Carbon with TiO ₂ Nanoparticles for Modulating Photocatalytic Reduction of CO ₂ to Methane

Poor adsorption and sulfate-induced high carrier recombination limit the CO2 photocatalytic reduction activity of TiO2 nanoparticles (anatase phase, average diameter ∼15 nm, and specific surface area 37.42 m2/g), as well as the generation of C–H added-value compounds. In this work, the difficulty of generating CH4 by photoreduction of CO2 on TiO2 was solved by constructing a composite of porous nitrogen-doped activated carbon (p-CN-2) with hierarchical nanochannels (5–20 nm), nanopores (<5 nm), and TiO2 nanoparticles. The introduction of p-CN-2 promoted the adsorption of CO2 and proton generation. Meanwhile, pyridine N in p-CN-2 interacts with TiO2 to establish a Ti–N–C photocarrier separation channel to enhance the effective photogenerated charge density. Promoted CO2, protons, and photocarrier concentrations modulate the occurrence of photocatalytic CO2 methanation on TiO2. The CH4 4 h yield of TiO2/p-CN-2 is 47.12 μmol·g–1, which is about 50 times higher than that of TiO2. The CH4 selectivity of TiO2/p-CN-2 increases from 15.53% TiO2 to 82.05%. This work presents a facile and effective method for facilitating photocatalytic CO2 methanation using TiO2 as a model. This work presents a facile and effective method for facilitating photocatalytic CO2 methanation using TiO2 nanoparticles as a model, and the prepared TiO2/p-CN-2 nanocomposite is particularly well-suited for solar-driven CO2 methanation in carbon recycling systems and renewable energy production (e.g., coupling with photovoltaic devices for green CH4 fuel synthesis).