abstract
Hydrates and clathrates have been suggested as potential gas separation and storage materials. For the case of hydrogen, previous results have evidenced that hydroquinone clathrates represent a feasible alternative for storage if compared to other options. The possibility of multiple clathrate cell occupation has been already demonstrated, so the key for a practical implementation of this solution is a detailed knowledge about the clathrate filling mechanism, and the upper occupancy limits. Identifying the optimal conditions required to enhance structure occupation, and the atomic scale nature of the inclusion process itself, leads to the possibility of increasing hydrogen volumetric storage capacity. In this study, the hydroquinone clathrate hydrogen filling process has been analyzed through atomistic Grand-Canonical Monte Carlo (GCMC) molecular simulations over a wide temperature and pressure range. The results obtained describe quantitatively the theoretical clathrate filling process, as well as the succession of multiple occupancy modes for the crystalline clathrate cells. The isotherms obtained have been correlated accurately using a mathematical model derived from the classical equation of Langmuir isotherms. The molecular simulation results presented describe the maximum hydrogen structural capacity, providing a valuable insight on the occurrence of multiple occupancy modes, a phenomenon not well described yet. The methodology used in this case can be extended to analyze hydrogen storage capacity inside other nanoporous materials.
authors
Brais Rodríguez-García, Germán Pérez-Sánchez, Martín Pérez-Rodríguez and Manuel M. Piñeiro
our authors
Germán Pérez-Sánchez
Assistant Researcheracknowledgements
M.M.P. acknowledges financial support from Spanish Ministerio de Ciencia e Innovación (MCIN), through grant Ref. PID2021-125081NBI00. M.P.R. acknowledges grant Ref. CNS2022-135881 financed by both MCIN/AEI/10.13039/501100011033 and NextGenerationEU/PRTR, and grant PID2023-151751NB-I00 funded by MCIN/AEI/10.13039/ 501100011033. CICECO-Aveiro Institute of Materials contributed this work under the projects UIDB/50011/2020, UIDP/50011/2020 &LA/P/0006/2020, financed by FCT/MEC (PIDDAC). G. P.-S. acknowledges the national funds (OE) through FCT -- Fundação para a Ciência e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29th, changed by Law 57/2017, of July 19th. The authors also acknowledge access to computing resources by Centro de Supercomputación de Galicia (CESGA, www.cesga.es, Finisterrae III Supercomputer).