Research advancement in molten salt-mediated thermochemical upcycling of biomass waste

The thermochemical upcycling of biomass into high value-added fuels and carbon materials in molten salts has attracted much attention in recent years. Molten salts have a wide variety of applications ranging from heat transfer fluids to storage media due to their thermal conductivity, dissolution ability, and high catalytic activity. Noteworthily, solar energy can be effectively stored in molten salts, providing high temperature heat for thermochemical conversion of biomass. Many efforts have been made in the development of molten salt-mediated thermochemical processes focusing on hydrolysis, pyrolysis and gasification. This paper discusses the advances in molten salt-mediated thermochemical conversion of biomass into chemicals, fuels and advanced carbon materials. The discussion is concentrated on the mechanisms of the molten salt-mediated thermochemical conversion of biomass. Moreover, fuels and carbon materials obtained by the pyrolysis and gasification processes are highlighted in the aspects of their synthesis processes and applications such as electrochemical applications (e.g., supercapacitors) and pollutant removal (e.g., adsorption and catalytic degradation). Furthermore, challenges and recommendations regarding various molten salt-mediated thermochemical conversions of biomass in the current stage are outlined.