Sahar Aghapour Ghourichay, Pier Carlo Ricci
Carbon-based nanomaterials (CBNs), such as graphene, carbon nanotubes (CNTs), and graphitic carbon nitride (g-C₃N₄), have become increasingly important in photocatalytic processes. This review examines current development in preparing these materials, new architectures, and integrating functionalities particularly focused on three important topics: (i) eliminating organic pollutants from wastewater, (ii) producing hydrogen via water splitting, and (iii) converting carbon dioxide into precious chemical compounds. For each carbon-based category, we evaluate multiple synthetic techniques as well as several morphologies ranging from 0-dimensional to three-dimensional systems. Special attention is given to techniques connected to the creation of heterojunctions inclusive of Z-scheme, S-scheme, and Schottky-kind interfaces. Key performance indicators, including degradation efficiency, quantum yield, response overpotential, product selectivity, and catalyst sturdiness, are evaluated. Additionally, the beneficial effects of mixing CBNs with cocatalysts like metals, metal oxides, and sulfides, along techniques for doping, tuning band gaps, and surface adjustments, are highlighted because of their considerable impacts on improving charge-transfer rates and overall photocatalytic interest. Given the rapid evolution and expansive research in this area, the review emphasizes the need of non-stop tracking and integration of recent insights. Staying current with emerging substances, reaction mechanisms, and hybrid catalytic systems is critical to developing realistic, efficient, and scalable photocatalytic answers for addressing urgent environmental and electricity demanding situations. This review provides a general overview linking synthesis, structure, and function of carbon-based photocatalysts, with particular focus on recent advances in heterojunction mechanisms and hybrid systems that bridge graphene, CNTs, and g-C₃N₄ architectures.