High-throughput Compositional Screening of PdTiH and PdNbH Hydrides for CO Reduction.

Electrochemical experiments and theoretical calculations have shown that Pd-based metal hydrides can perform well for the CO reduction reaction (CORR). Our previous work on doped-PdH showed that doping Ti and Nb into PdH can improve the CORR activity, suggesting that the Pd alloy hydrides with better performance are likely to be found in the PdTiH and PdNbH phase space. However, the vast compositional and structural space with different alloy hydride compositions and surface adsorbates, makes it intractable to screen out the stable and active PdMH catalysts using density functional theory calculations. Herein, an active learning cluster expansion (ALCE) surrogate model equipped with Monte Carlo simulated annealing (MCSA), a CO* binding energy filter and a kinetic model are used to identify promising PdTiH and PdNbH catalysts with high stability and superior activity. Using our approach, we identify 24 stable and active candidates of PdTiH and 5 active candidates of PdNbH. Among these candidates, the PdTiH, PdTiH, and PdNbH are predicted to display current densities of approximately 5.1, 5.1 and 4.6 μA cm at -0.5 V overpotential, respectively, which are significantly higher than that of PdH at 3.7 μA cm.