Surface-amino-induced boosting solar conversion of CO₂ to CO over natural metal-free catalyst

Design and construction of visible-light-responsive and low-cost catalyst to improve photocatalytic CO₂ reduction efficiency are highly urgent due to rapid increment of CO₂ emission. Herein, a facile but effective strategy is proposed to synthesize heteroatoms-doped porous treated rape pollen (TRP) and NH₂-functionalized TRP for CO₂ reduction. Heteroatoms doping can accelerate photoinduced charge transfer between neighboring carbon atom. The introduction of NH₂- group offers effective sites to boost CO₂ adsorption, which is beneficial to facilitate CO₂-to-CO conversion. The experimental results indicate that TRP-NH₂ exhibits visible-light-driven CO formation rate of 1165.3 μmol h⁻¹ g⁻¹ in the gas-solid reaction system without co-catalysts or sacrificial agents, which is 2.4 and 70.1 times than those of TRP (488.4 μmol h^-1 g^-1) and g-C₃N₄ (16.6 μmol h^-1 g^-1), and exceeds reported state-of-the-art carbon-based photocatalysts. The theoretical investigation shows that the incorporation of NH₂- group can improve its charge density and converge more electrons to adsorb CO₂ molecules. In situ Fourier transform infrared (FT-IR) spectroscopy spectra disclose that the COOH* radical is the main intermediate. The findings reveal the correlation between surface NH₂- group and photocatalytic CO₂ reduction performance and can be extended to other sustainable metal-free based catalysts for solar-driven CO₂ reduction.