General impurity gas blanket effect mechanism and elimination strategies for hydrogen storage materials

Abstract

Hydrogen energy has attracted considerable attention as the promising alternative to fossil energy. However, pollutants in H2 inevitably affect the hydrogenation kinetics of hydrogen storage materials (HSMs). In this work, the general physical blanket effect mechanism of impurity gases (He/Ar/CH4/N2/CO2/NO2) on the hydrogenation kinetics is extracted and confirmed to be a single physical process unrelated to HSMs for the first time. Specifically, the selective absorption of H2 by HSMs induces the local enrichment of impurity gases and impede H2 diffusion physically. For example, ZrCo can achieve its theoretical capacity (2.0 wt% H2) in 1.2 bar pure H2 within 40 s, while only 0.46 wt% H2 could be absorbed in 1.2 bar 3 mol% CH4 + 97 mol% H2 mixed gas even after 0.4 h. Such blanket effect may interlace with chemical surface poisoning effect and bring variability on hydrogenation kinetics. Notably, among the investigated impurity gases, He/Ar/N2/CH4 are absolute inactive gases which cannot impede hydrogenation, thus excluding the chemical surface poisoning effect originated from active gases. This allows the precise extraction of intrinsic physical blanket effect quantitatively, instructing comprehensive strategies to promote the fast hydrogenation saturation for HSMs. In summary, optimizing engineering parameters including dynamical hydrogenation operation provides an effective approach to remarkably promote hydrogen absorption kinetics of HSMs.