Work

Depth-resolved operando grazing-incidence diffraction reveals non-equilibrium Cu-Pt alloy restructuring under glycerol electrooxidation

Year: 2026

Type: preprint

Abstract: Alloying Pt with Cu enhances activity towards hydrogen generation and valueadded products during the electrooxidation of glycerol, but the most active alloys typically require electrochemical activation, during which their structure and composition evolve in poorly understood ways. Here we use synchrotron-based operando, angle-dependent grazing incidence X-ray diffraction in a custom dual-chamber electrochemical flow cell to follow, in real time, the depth-resolved structural evolution of Cu-Pt thin-film catalysts under glycerol electrooxidation in alkaline media. Our approach allows us to monitor the temporal evolution of lattice parameter, phase composition and microstrain during cyclic voltammetry and chronoamperometry while varying the X-ray penetration depth from the topmost tens of nanometres into the underlying alloy. For Cu-rich Cu92Pt8 catalysts, we observe substantial restructuring of the near-surface region, including the cyclic formation and reduction of Cu2O, pronounced Cu leaching from depths of several tens of nanometres, and the progressive emergence of a Pt-rich ≈Cu15Pt85 phase that stabilises the surface against further oxidation. These structural changes coincide with a ca. 5-fold increase in current density and a ca. 100 mV increase in onset potential during activation, after which the electrochemical response becomes stable. Pt-richer alloys exhibit markedly reduced restructuring, with compositional changes largely confined to the top ≈20-30 nm of the catalyst. Analysis of peak broadening via Williamson-Hall plots reveals that dealloying and surface oxidation are associated with increased microstrain, which subsequently relaxes as a Pt-rich surface configuration is established. Beyond revealing the non-equilibrium interplay of oxidation, segregation and realloying that governs the performance and durability of Cu-Pt catalysts for glycerol electrooxidation, our methodology and cell design provide a flexible, broadly applicable platform for operando, depth-resolved diffraction studies of electrochemical interfaces in energy and biomass-conversion reactions.

Source: ChemRxiv

DOI: 10.26434/chemrxiv.15010183/v1