Biomass-derived hydrothermal carbonization carbon: a carbon-negative photocatalytic platform

Biomass is a carbon-neutral resource, as its organic carbon is derived from atmospheric CO₂. Hydrothermal carbonization offers an economical and environmentally sustainable method for converting biomass into hydrothermal carbonization carbon (HTCC), which has recently emerged as a carbon-negative photocatalytic platform. This critical review first outlines the chemical mechanisms involved in the formation of HTCC from biomass. It then presents a systematic analysis of the hydrothermal conditions that influence carbonization behavior. Furthermore, the photocatalytic applications of HTCC in environmental remediation, energy conversion, and organic transformation are comprehensively reviewed. Key challenges and future prospects for HTCC in photocatalytic applications are also discussed. The review aims to offer theoretical guidance and experimental insights for the development of HTCC-based materials and their application in photocatalysis.