Mass transfer driven pore engineering of activated carbon from the activation of biomass

Abstract

The performance of activated carbon (AC) from biomass relies on the precise control of its pore structure. Pore development during the activation of biomass is essentially a dynamic process driven by the mass transfer of volatiles and the derivatives of activators. Therefore, this review systematically analyzes the mass transfer regulation mechanism in various scenarios for the preparation of AC with different biomass feedstocks under distinct reaction conditions. The discussion first elaborates on how pyrolysis methods (microwave heating vs. conventional conductive heating), temperature gradients, and raw material composition affect the release of volatiles, diffusion pathways, carbon skeleton shrinkage behavior, and the initial reaction network for the formation of the pore structure. The etching mechanisms and mass transfer characteristics of diverse activating agents are also discussed to reveal how pore architecture and surface chemistry are governed by the infiltration/melting/diffusion of activating agents, penetration depth, and interfacial reactions with biomass constituents. Based on mass transfer mechanisms, this study further proposes targeted design strategies for tailoring the pore and chemical properties of AC for various application scenarios (gas and macromolecular pollutant adsorption, supercapacitors, and advanced oxidation) and highlights emerging green pathways to steer the sustainable production of AC, providing new methodological support for the controllable preparation of high-performance functional carbon materials with desirable properties.