Direct Hydrogen Storage From Water to Diphenylmethane via Liquid Organic Hydrogen Carrier Electrochemical Hydrogenation System

초록

This study presents a novel electrochemical hydrogenation (EH-DPM) system that integrates clean hydrogen production and storage by utilizing a diphenylmethane (H0-DPM, DPM) /dicyclohexylmethane (H12-DPM, DCM) pair as a liquid organic hydrogen carrier (LOHC). The system operates in a full-cell configuration, coupling a cathode for the electrochemical hydrogenation of H0-DPM (EH-DPM) with a proton exchange membrane water electrolyzer (PEMWE) anode, thereby enabling direct hydrogen storage in the LOHC during water splitting. The EH-DPM system demonstrates higher energy efficiency than conventional PEMWE, achieving reaction currents at lower potentials. A comparative testing of Pt and Ru black electrocatalysts reveals that Ru black outperforms Pt black at higher voltages (> 1.5 V), achieving significantly higher selectivity (92.3% at 1.6 V) for the fully hydrogenated H12-DPM. H-1-NMR and C-13-NMR analyses identifies cyclohexylmethylbenzene (H6-DPM, CMB) as the sole hydrogenation intermediate, highlighting that optimal electrocatalyst selection is crucial for maximizing H12-DPM yield and minimizing energy losses from intermediate formation. Density functional theory calculations elucidate catalyst-dependent reaction pathways and show that distinct hydrogen migration barriers on Pt and Ru surfaces account for the observed voltage-dependent selectivity. These findings suggest that Ru black is a promising electrocatalyst for developing commercially viable hydrogen storage technologies based on the EH-DPM system.

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