Hydrogen Production via Efficient Formic Acid Decomposition: Engineering the Surface Structure of Pd-Based Alloy Catalysts by Design

Improving the activity and selectivity of Pd-based alloy catalysts for hydrogen production from formic acid decomposition is still a challenge. We have performed a comprehensive study, on the basis of available experimental data, of the relationship between the surface structure of Pd-based alloy catalysts and their catalytic activities for formic acid decomposition by using density functional theory and Sabatier analysis. Importantly, the average Bader charge of Pd atoms on the surface and the average bond length of the surface atoms are identified as two quantitative descriptors for analyzing the effect of charge redistribution and surface tension on the reactivity of the Pd-based alloy catalysts. On the basis of the two descriptors, we propose a strategy for rationally engineering the surface structure of Pd-based alloy catalysts by introducing suitable dopants and by devising optimal atomic arrangements. The strategy allows us to identify the potential candidates: PdAu and PdAg alloy with specific atomic arrangements. We find that these alloy catalysts are superior to the state-of-the-art systems tested in previous experiments. Our strategy may be generalized for designing heterogeneous alloy catalysts beyond formic acid decomposition.