Giant improvement in piezo-photocatalytic capability of colloidal g-C3N4 quantum dots

Piezo–photocatalysis has emerged as a promising strategy for addressing energy and environmental challenges by synergistically harnessing light and mechanical energy. In this study, colloidal g-C₃N₄ quantum dots (QD) are synthesized via a high-power ultrasonic exfoliation method and have demonstrated significantly enhanced piezo–photocatalytic performance. Key factors for performance enhancement include reduced size, enhanced surface effects, and the introduction of oxygen doping and nitrogen vacancy, which improve the separation efficiency and lifetime of photogenerated charge carriers. These enhancements enable exceptional photocatalytic and piezo–photocatalytic degradation efficiencies, achieving 99.9 ​% degradation of methylene blue within 20 ​min under 365 ​nm light irradiation combined with ultrasonic assistance. Furthermore, in-situ electron spin resonance measurements reveal the abundant generation of ·CH₂OH radicals in melamine-derived g-C₃N₄ QD, highlighting its potential for applications in photocatalytic organic synthesis. The colloidal QD exhibit remarkable long-term stability and reusability, with minimal performance decline over multiple cycles. This work elucidates the mechanisms underlying the performance enhancements of g-C₃N₄ QD and underscores their potential for practical applications in environmental remediation and sustainable energy conversion.