Hierarchical Co@C catalysts derived from metal-organic frameworks with tailored particle sizes for enhanced MgH2 hydrogen storage
Fei Li, Yue Wang, Yue Wang, Yuqi Wang, Yuqi Wang, Guancheng Ou, Shuang Cheng, Sinan Guan, Jia Meng, Le Wu, Xin Ding, Gang Xie
Abstract
MOF-derived catalysts have been widely investigated to enhance the catalytic activity of MgH 2 due to their highly adjustable morphology and abundant active sites. While significant efforts have been made to improve the catalytic performance of these materials, the effect of particle size gradation has not been systematically investigated. Herein, a series of hierarchical Co@C-x (x = S, M, L) catalysts with controlled particle sizes were synthesized by tailoring the crystallization conditions of ZIF-67 and systematically investigated for their catalytic effects on MgH 2 hydrogen storage. The results reveal that reducing the particle size of ZIF-67-derived Co@C catalysts significantly enhances hydrogen absorption and desorption kinetics. Among the samples, MgH 2 -Co@C-S with the smallest particle size exhibits an initial dehydrogenation temperature of 194 °C, which is 176 °C lower than that of pure MgH 2 , while the activation energy for desorption decreases to 93.1 kJ/mol. Moreover, it maintains 97.92 % of its hydrogen storage capacity after multiple cycles without notable degradation. This enhancement is attributed to the “hydrogen pump” effect induced by the in situ formation of Mg 2 Co/Mg 2 CoH 5 , nanoscale surface effect, as well as the presence of carbon species that stabilize the MgH 2 matrix by preventing particle aggregation. These findings provide new insights into the size-dependent catalytic behavior of MOF-derived materials and highlight the importance of hierarchically structured catalysts in optimizing MgH 2 hydrogen storage performance.