Research on biochar prepared by trace KOH catalyzed CO2 activation vs KOH activation as advanced candidate for carbon capture

Abstract

The technology for green and macro-conversion of solid waste biomass to prepare high-quality activated carbon demands urgent development. This study proposes a technique for synthesizing carbon adsorbents using trace KOH-catalyzed CO₂ activation. Comprehensive investigations were conducted on three aspects: physicochemical structure evolution of biochar, mechanistic understanding of trace KOH-facilitated CO₂ activation processes, and application characteristics for CO₂ adsorption. Results demonstrate that biochar activated by trace KOH (<10%) and CO₂ achieves comparable specific surface area (1244.09 m²/g) to that obtained with 100% KOH activation (1425.10 m²/g). The pore structure characteristics (specific surface area and pore volume) are governed by CO and CH₄ generated through K-salt catalyzed reactions between CO₂ and biochar. The optimal CO₂ adsorption capacities of KBC adsorbent reached 4.70 mmol/g (0 °C) and 7.25 mmol/g (25 °C), representing the maximum values among comparable carbon adsorbents. The 5%KBC-CO₂ sample exhibited CO₂ adsorption capacities of 3.19 and 5.01 mmol/g under respective conditions, attaining current average performance levels. Notably, CO₂/N₂ selectivity (85:15, volume ratio) reached 64.71 at 0.02 bar with robust cycling stability. Molecular dynamics simulations revealed that oxygen-containing functional groups accelerate CO₂ adsorption kinetics and enhance micropore storage capacity. This technical route offers simplicity, environmental compatibility, and scalability, providing critical references for large-scale preparation of high-quality carbon materials.