Abstract

Ammonia borane (NH3BH3, AB) is a promising chemical hydrogen carrier due to its high hydrogen content; however, achieving efficient low-temperature hydrogen release remains challenging. In this work, we perform a density functional theory (DFT) study of AB adsorption and dehydrogenation on the TiC(001) surface and on Au2Pt2 clusters supported on TiC(001), elucidating the roles of both the carbide support and the bimetallic cluster in controlling hydrogen-release mechanisms. The clean TiC(001) surface actively participates in AB activation, promoting sequential B-H and N-H bond cleavage with moderate activation barriers (0.62 and 0.31 eV). In contrast, the presence of supported Au2Pt2 clusters dramatically enhances catalytic performance, rendering the first hydrogen-release step from the-BH3 fragment essentially barrierless. This behavior is confirmed by CI-NEB calculations and finite-temperature molecular dynamics simulations, which reveal fast hydrogen dissociation occurring within a few picoseconds even at room temperature. Subsequent hydrogen spillover from Pt sites to surface carbon atoms and further hydrogen dissociation steps proceed through exceptionally low activation barriers (<0.30 eV). Compared with a wide range of reported catalytic systems, Au2Pt2/TiC(001) exhibits one of the lowest energy requirements for initiating AB dehydrogenation. These results highlight the strong synergistic effect between bimetallic Au-Pt clusters and polar carbide support, providing valuable design principles for efficient heterogeneous catalysts for hydrogen release from chemical hydrogen carriers. The observed behavior is consistent with a cooperative Au-Pt effect, supported by our previous comparisons with monometallic Au4 and Pt4 clusters for H2 dissociation.