Constructing Mg2Co–Mg2CoH5 nano hydrogen pumps from LiCoO2 nanosheets for boosting the hydrogen storage property of MgH2

Abstract

Herein, an active positive electrode material, LiCoO₂ nanosheets, was synthesized via a two-step method, which demonstrated a remarkable catalytic effect for the hydrogen storage property of MgH₂. Incorporated with LiCoO₂ nanosheets, MgH₂ started to release hydrogen at 180 °C and a desorption content as high as 5.5 wt% H₂ was attained within 60 min at 250 °C. The dehydrogenation activation energy was significantly decreased to 48.5 ± 0.4 kJ mol⁻¹, achieving a 68.9% reduction compared to MgH₂. It was verified by microstructural studies that Li⁺ served as an “anchor” to facilitate a uniform distribution of LiCoO₂ “boat” among the MgH₂ “ocean”, benefitting the self-assembly of numerous Mg₂Co–Mg₂CoH₅ couples on the surface of MgH₂ during the cycling process. Meanwhile, the in situ formed Mg₂Co–Mg₂CoH₅ couples were not restricted to offering multiple channels for fast hydrogen diffusion but also worked as “nano hydrogen pumps” to accelerate Mg/MgH₂ hydrogen charging and discharging. This study provides an interesting example of effective cooperation between Li⁺ and Co³⁺ on improving the catalytic action toward MgH₂. It shall shed light on efficient designing of high-efficient catalysts in hydrogen storage areas or other energy-related fields.