# name
Bimetallic PtX Nanoalloys as HER Catalysts

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Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2026, Tutors: Albert Bruix Fusté, Emanuele Telari

# metadata.dc.description.abstract[].value
The hydrogen evolution reaction (HER) is one of the most promising pathways towards clean hydrogen production, with pure platinum nanoparticles standing as the benchmark catalyst. However, the high cost of platinum drives the search for alloyed alternatives capable of retaining comparable catalytic performance at reduced expense. In this work, PtCu, PtAg, PtAu and PtNi nanoalloys of 201 atoms are investigated across three stoichiometries (Pt:X = 3:1, 1:1, 1:3), with the dual aim of determining their equilibrium chemical ordering and evaluating their hydrogen adsorption energetics toward HER.
Structural optimization is carried out via Monte Carlo global optimization using two surrogate energy models of different complexity: the topological (TOP) method and the MACE-MP-0b (Agnesi) machine learning interatomic potential. MACE consistently yields lower-energy and structurally richer chemical orderings than TOP and is adopted as the reference framework. The resulting structures reveal two distinct segregation regimes: Pt segregates to the surface in PtNi, PtCu and PtAg, while Au dominates corner and edge positions in PtAu, a result driven by the relativistic destabilization of Au heterometallic bonds, which causes Au to minimize contacts with Pt and preferentially occupy low-coordination surface positions. Hydrogen adsorption energies are subsequently computed across all surface sites using MACE-MP-0b, totalling 3,876 calculations across the twelve systems.
Pt151Cu50 emerges as the most promising candidate, combining 147 sites near the thermodynamic optimum (ΔEH ≈ −0.24 eV) through a mechanistically sound ligand and strain activation of surface Pt by subsurface Cu, at a fraction of the cost of pure platinum. Pt151Ni50 presents the most clearly defined activation mechanism: a pure Pt surface modulated exclusively by subsurface Ni via the ligand and strain effects established in Section 6.1, reproducing the Pt-skin/Ni-subsurface architecture known experimentally for exceptional catalytic activity. PtAu heterometallic sites represent an unexpected durability-activity compromise. PtAg is not recommended as a HER candidate in any stoichiometry studied. A broader methodological finding is that the number of sites within a thermodynamic descriptor window is not a sufficient criterion for catalyst ranking on its own; the electronic mechanism through which those sites achieve their adsorption energy must also be considered, as it determines their true catalytic relevance

# metadata.dc.rights[].value
cc-by-nc-nd (c) Romeo Barceló, Albert, 2026

# metadata.dc.title[].value
Bimetallic PtX Nanoalloys as HER Catalysts