Critical role of CoO modification on Pt/Al2O3 for efficient H18-DBT dehydrogenation in LOHC systems

Abstract

Liquid organic hydrogen carriers (LOHCs) represent a highly promising strategy for hydrogen storage and long-distance transport, offering a safe and economically viable solution to key infrastructure challenges. The effective application of LOHCs requires dehydrogenation catalysts that strike an optimal balance between activity and stability. Herein, we report a precisely engineered CoO_x-modified Pt/Al₂O₃ catalytic system that exhibits outstanding performance in the dehydrogenation of perhydro-dibenzyltoluene (H18-DBT). Systematic investigations identify a critical CoO_x loading threshold at 1 wt%, at which the catalyst achieves a maximum dehydrogenation degree (DoD) of 93% and a H₂ production rate of \(20.98\times 10^{3}\ \text{mol}_{\mathrm{H}_{2}}\cdot \text{mol}_{\text{Pt}}^{-1}\cdot \mathrm{h}^{-1}\) at 300 °C for dehydrogenation, outperforming all the catalysts reported in the literature. However, increasing the Co loading from 1 to 10 wt% results in a sharp decline in DoD from 93% to 7.2%. With the increasing CoO_x content, the cobalt species initially form amorphous CoO clusters, which subsequently transform into crystalline Co₃O₄. The amorphous CoO is found to be the key species responsible for enhanced dehydrogenation activity by increasing the electron density and reducing the particle size of Pt, thereby promoting dehydrogenation while suppressing the hydrogenation capability.