Harnessing Carbon Dots for Photocatalytic Energy Conversion: Challenges and Opportunities

The efficient conversion of solar energy into chemical energy is vital for achieving decarbonization and sustainable development. Central to this effort is the development of photocatalysts that are cost-effective, stable, and multifunctional. Carbon dots (CDs), owing to their simple synthesis and tunable photophysical and redox properties, have emerged as promising candidates in this field. However, their broader application is limited by inherent structural heterogeneity. Gaining deeper insights into synthesis conditions can enable the design of CDs with tailored structures and properties, thereby enhancing their photocatalytic performance. Equally important is the identification of catalytically active sites within the complex CD structure and a clearer understanding of the underlying photocatalytic mechanisms. This review provides an overview of CD-based photocatalytic systems, focusing on their structural characteristics and associated photocatalytic behaviors. It then explores advanced strategies to improve performance, particularly through improved charge management and charge-induced surface reactions. Furthermore, the review highlights the multifunctional roles that CDs can play-serving as photosensitizers, co-catalysts, or integrated photocatalysts-in key applications such as hydrogen evolution, hydrogen peroxide production, and carbon dioxide reduction. Finally, the review outlines design rationales and emerging opportunities for high-performance CD-based photocatalysts in sustainable energy applications.