Tailoring the Pore Size, Basicity, and Binding Energy of Mesoporous C3 N5 for CO2 Capture and Conversion

Abstract

We investigated the CO₂ adsorption and electrochemical conversion behavior of triazole-based C₃ N₅ nanorods as a single matrix for consecutive CO₂ capture and conversion. The pore size, basicity, and binding energy were tailored to identify critical factors for consecutive CO₂ capture and conversion over carbon nitrides. Temperature-programmed desorption (TPD) analysis of CO₂ demonstrates that triazole-based C₃ N₅ shows higher basicity and stronger CO₂ binding energy than g-C₃ N₄ . Triazole-based C₃ N₅ nanorods with 6.1 nm mesopore channels exhibit better CO₂ adsorption than nanorods with 3.5 and 5.4 nm mesopore channels. C₃ N₅ nanorods with wider mesopore channels are effective in increasing the current density as an electrocatalyst during the CO₂ reduction reaction. Triazole-based C₃ N₅ nanorods with tailored pore sizes exhibit CO₂ adsorption abilities of 5.6-9.1 mmol/g at 0 °C and 30 bar. Their Faraday efficiencies for reducing CO₂ to CO are 14-38% at a potential of -0.8 V vs. RHE.

Keywords: CO2 capture; CO2 reduction; carbon nitrides; porous materials; triazole.