Largely elevated photocatalytic hydrogen generation over Eu doped g-C3N4 photocatalyst

Graphitic carbon nitrides (g-C3N4) have come into researchists' horizons for their diversified merits, such as the especial graphite-phase 2D laminar framework, competitive price, innoxious, eligible bandgap (similar to 2.7 eV) and acceptable consistency. Whereas limited by the disadvantages of inferior specific surface area and fast recombination of photo-generated charge pairs, the pragmatic applicability of g-C3N4 turns out to be still lacking. In our work, g-C3N(4) (GCN) and Eu-doped g-C3N4 (Eu/CN) with different Eu/g-C3N4 molar ratios (1%, 2%, 3%, 4%) were synthesized by an impregnating method and characterized through a series of measurements. Photocatalytic activities of Eu/CN catalysts manifest preeminent H-2 generation capacity and stability excited by solar light. The highest H-2 generation rate without any co-catalyst is 128.8 mu mol g(-1) h(-1) over the 3% Eu/CN, achieving 117.1-fold as high as that of GCN (1.1 mu mol g(-1) h(-1)). Eu doping is proven to slightly widen the bandgap of the samples, resulting in the conduction band of samples more negative and the reduction reaction more effortlessly. Simultaneously, Eu doping changes the molecular structure of g-C3N4 and forms more nitrogen defects. Photo-excited electrons can be captured by the defective sites derived from the defect levels, and the recombination rate of photoinduced carriers will be significantly inhibited, accordingly facilitating the high-efficiency separation of photo-induced carriers and improving photocatalytic efficiency. This study provides an advantageous instruction for the implementation of rare earth metals application in improving the separation and transfer rate of photo-induced electrons (e(-)) and holes (h(+)) over g-C3N4. (C) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Graphitic carbon nitrides (g-C3N4) have attracted researchers' attention for their special 2D laminar structure, competitive price, non-toxicity, suitable bandgap, and acceptable consistency. However, the practical application of g-C3N4 is still limited due to its low specific surface area and fast recombination of photo-generated charge pairs. In this study, Eu-doped g-C3N4 (Eu/CN) catalysts with different Eu/g-C3N4 ratios were synthesized and characterized, showing excellent H-2 generation capacity and stability under solar light. Eu doping widened the bandgap, changed the molecular structure, and formed more nitrogen defects in g-C3N4, leading to improved photocatalytic efficiency by inhibiting the recombination of photoinduced carriers. This study provides valuable insights for using rare earth metals to enhance the separation and transfer rate of photo-induced electrons and holes over g-C3N4.