Construction of a graphitic carbon nitride-based photocatalyst with a strong built-in electric field via π–π stacking interactions boosting photocatalytic CO2 reduction

Abstract

Solar-driven photocatalytic reduction of carbon dioxide (CO₂) into fuels, particularly over a graphitic carbon nitride (GCN)-based photocatalyst, presents a promising solution to address energy and CO₂ emission issues. However, the limited charge-carrier dynamics significantly hampers the photocatalytic performance of CO₂ reduction. Enhancing the built-in electric field at the interface has been revealed as an effective strategy to improve the activity of photocatalytic reactions. In this work, a high-efficiency photocatalyst TPNCNm was fabricated by anchoring sodium 2,5,8-tri(4′-pyridyl)-1,3,4,6,7,9-hexaazaphenalenate (TPHAP), with a similar tri-s-triazine unit to GCN, on the surface of crystalline nitride carbon (NCN) via π–π stacking interactions. The fabricated photocatalyst TPNCNm demonstrates efficient solar-driven CO₂ reduction into CO and CH₄ through the gas–solid mode, with evolution rates of CO and CH₄ reaching 10.43 and 4.88 μmol g⁻¹ h⁻¹, respectively. Furthermore, the investigation of the band structure and charge carrier dynamics revealed the formation of a strong built-in electric field between TPHAP and NCN. The directional built-in electric field from NCN to TPHAP effectively accelerated the charge carrier separation and migration, thereby boosting CO₂ photoreduction performance. In addition, theoretical calculations have verified that TPHAP molecules not only serve as active sites, but also effectively lower the Gibbs free energy of crucial intermediate COOH*, which is the rate-determining step for CO₂-to-CO photoreduction. This work highlights the importance of utilizing coplanar materials to construct efficient hybrid graphitic nitride carbon-based photocatalysts with a strong built-in electric field through π–π interactions for enhanced photocatalytic CO₂ reduction.