Biomolecular l-tryptophan as a hole mediator anchored on g-C3N4 exhibits remarkably enhanced photocatalytic H2 evolution

Abstract

Photocatalytic water splitting is a promising approach to solar-to-fuel conversion. In recent years, graphitic carbon nitride (g-C₃N₄) has triggered worldwide interest due to its eco-friendliness, low cost, and visible-light activity as a semiconductor polymer photocatalyst. However, rapid recombination of photoinduced charge carriers and low efficiency are key issues hindering the practical application of g-C₃N₄ in the efficient photocatalytic hydrogen (H₂) production field. Herein, we fabricate a novel g-C₃N₄-based composite coupled with levorotatory-tryptophan (denoted as CN/L-trp) through π–π interactions and hydrogen bonds to improve the photocatalytic performance. The redox amino acid L-trp small biomolecules act as a hole relay and thus accelerate the transfer process of holes from g-C₃N₄ to triethanolamine (TEOA), which leads to more electrons shuttled to a Pt cocatalyst, and finally boosts the visible-light photocatalytic H₂ evolution reaction (HER). When introducing 10 wt% L-trp, the photocatalytic H₂ production rate of g-C₃N₄/10 wt% L-trp (CN/10 wt% L-trp) loaded with 1.0 wt% Pt cocatalyst composite is prominently enhanced up to 1046.0 μmol h⁻¹ g⁻¹, which is four times that of g-C₃N₄ loaded with 1.0 wt% Pt cocatalyst (260.2 μmol h⁻¹ g⁻¹). Our study provides a novel strategy to develop an efficient, green and stable g-C₃N₄-based hybrid photocatalyst for potential application in solar-to-hydrogen energy conversion.