New perspectives on the effects of texture and chemical properties on the hydrogen storage capacity of biochar at room temperature

Analyzing the effects of texture and chemical structure on hydrogen adsorption performance at room temperature can provide a theoretical basis for accurately constructing carbon-based hydrogen adsorbents. Based on thermal regulation technology, the biochar with different specific surface areas (803.85–2801.88 m²/g) and oxygen content (21.57–41.86%) was successfully prepared by the two-step “carbonization-activation” method. Various characterization methods were used to explore the relationship between the physicochemical structure and hydrogen adsorption characteristics at room temperature. The results show that the hydrogen storage characteristics of biochar at room temperature are controlled by specific surface area, oxygen content, and acidic surface groups. The boundary conditions for promoting/inhibiting hydrogen adsorption are related to oxygen content. In different pressure regions, specific surface area, oxygen content, and the acid surface group have different degrees of effect on hydrogen adsorption, and oxygen content has the most significant impact. The Freundlich model accurately fits the hydrogen adsorption process at room temperature. Among the carbon-based hydrogen storage materials, biochar has excellent hydrogen storage performance, with an adsorption capacity of 0.52 wt% at 50 bar.