Multifaceted Regulation of Water Autodissociation Species on Interfacial Evolution and Methane Adsorption under...

This study investigates the disturbance effects of H₂O, H₃O⁺, and OH^- on CH₄ adsorption-desorption and interfacial stability, which is of great scientific significance for optimizing material properties and revealing competitive adsorption and hydrogen-bond-mediated interfacial stress in coal pores. Using molecular simulations and experiments, we introduced these species into coal micro-nanopores to regulate the medium environment and surface charge and analyzed the hydrogen-bond network, CH₄ adsorption and diffusion, and mechanical response of coal. The results show that H₃O⁺ is more mobile than OH^- in single systems, while the reverse occurs in mixed systems due to ion interference in hydrogen-bond networks. The H₂O-dominated system shows a compact hydrogen-bond network and strong CH₄ adsorption, followed by the mixed system, whereas H₃O⁺- or OH^--dominated systems present fragmented hydrogen bonds and weaker CH₄ adsorption. Additionally, charge heterogeneity in mixed systems induces severe local structural damage in coal. HCl treatment damages coal mechanically, reducing micropore adsorption but enhancing macropore adsorption, while NaOH generates new micropores via alkali etching for gas storage. Consequently, the HCl system shows higher overall CH₄ adsorption, but the NaOH system exhibits greater CH₄ uptake in micropores, verifying that OH^--dominated media favor higher CH₄ adsorption and binding energy than H₃O⁺-dominated ones. This work enables effective regulation of coal structure and gas adsorption performance, providing new approaches for clean and efficient coal utilization.