Promoting Pt/Al₂O₃ Catalysts with Fe, Mn, and Co for Enhanced LOHC Dehydrogenation.

Introduction

Hydrogen is a key energy carrier, but storage challenges persist. LOHCs like DBT offer a viable solution, though reliance on noble metals limits scalability. This work explores Fe, Mn, and Co as promoters to enable more sustainable LOHC catalysis.

Methods

The catalysts were prepared by wet impregnation and characterised by nitrogen adsorption-desorption and hydrogen pulse chemisorption. Catalytic performance was evaluated in hydrogenation using a 600 mL autoclave-type reactor (Parr, Type 4568) at 50 bar and 290 °C, while dehydrogenation was carried out in a spherical flask, at atmospheric pressure and the same temperature.

Results

This study evaluates Pt-based bimetallic catalysts containing non-precious metals (Fe, Mn, and Co). The Pt loading was kept constant at 0.25 wt%, while Fe, Mn, and Co loadings were varied at 0.1, 0.25, and 0.5 wt%. The catalysts were tested in both hydrogenation and dehydrogenation reactions and compared with a monometallic Pt catalyst. In dehydrogenation, all bimetallic catalysts achieved higher degrees of dehydrogenation, representing 10% enhancement over the monometallic catalyst, with performance improving as the secondary metal loading increased. This enhancement is attributed to electronic modifications of Pt induced by alloy formation, which facilitate H* desorption, as well as to the presence of Fe, Mn, and Co oxides that act as hydrogen acceptors, promoting H* spillover and H₂ release while preserving active Pt sites. In contrast, hydrogenation activity decreased with increasing Fe, Mn, or Co loading due to weakened Pt–H₂ interactions caused by alloying and to the partial coverage of Pt active sites by metal oxides, which hinder H₂ dissociation and reduce Pt affinity for H0-DBT.

Conclusion

Additives are a promising strategy for catalytic systems in organic liquids.