Highly Efficient and Stable Potassium-Doped g-C3N4/Zn0.5Cd0.5S Quantum Dot Heterojunction Photocatalyst for Hydrogen Evolution

Abstract

The advancement of efficient and robust photocatalysts for water splitting is pivotal for the sustainable production of clean hydrogen energy. This study introduces a novel photocatalyst, synthesized by integrating 0D Zn_0.5Cd_0.5S quantum dots (ZCS QDs) onto 2D K⁺-doped graphitic carbon nitride (K-CN) microribbons, via an in-situ hydrothermal growth method. A comprehensive characterization was performed to assess the optical characteristics, structural attributes, and charge transfer efficacy of the prepared photocatalysts. Our findings reveal that the incorporation of K⁺ ions effectively modulates the bandgap and valence band positions of g-C₃N₄, facilitating an optimal energy level alignment with ZCS QDs. Moreover, the integration of ZCS QDs improves the photon capture ability and concurrently diminishes the recombination rate of photogenerated charge carriers. The optimized ZCS 51%/K-CN photocatalyst demonstrates a promising simulated sunlight-driven hydrogen production rate of 9.606 mmol·h⁻¹·g⁻¹, surpassing that of pristine ZCS QDs by nearly three times, without the need for noble metal co-catalysts. Most notably, the photocatalyst maintains its hydrogen evolution performance consistently over five photocatalytic cycles, underscoring its stability. The remarkable photocatalytic activity is primarily ascribed to the formation of a type-II heterojunction between K-CN and ZCS QDs, which enhances charge separation and transfer. This research represents a significant step forward in the design of heterojunction photocatalysts by merging QDs with g-C₃N₄, offering a highly effective and durable solution for photocatalytic hydrogen production.