Does H₂ Temperature-Programmed Reduction Always Probe Solid-State Redox Chemistry? The Case of Pt/CeO₂

Area of Science:

• Catalysis
• Surface Science
• Materials Science

Background:

• Redox reactions on transition metal oxides are crucial for catalysis.
• Hydrogen temperature-programmed reduction (H2-TPR) is a common method to study oxide reducibility.
• H2-TPR assumes H2 consumption rate is limited by oxide reduction, overlooking intermediate steps.

Purpose of the Study:

• To investigate the elementary steps probed by H2-TPR.
• To evaluate H2 consumption kinetics over CeO2 and Pt/CeO2 catalysts.
• To clarify the influence of platinum on H2-TPR characteristics.

Main Methods:

• Kinetic analysis of H2 consumption over CeO2 and Pt/CeO2 with varying Pt loadings.
• Evaluation of H2-TPR over samples with mixed Pt single-atoms and nanoclusters.
• Deconvolution of H2 dissociation, H-spillover, and surface reduction steps.

Main Results:

• H2 consumption rate in H2-TPR is primarily determined by H-spillover at Pt-CeO2 interfaces.
• The rate is controlled by H2 dissociation on Pt nanoclusters, not CeO2 reducibility.
• Lower temperature H2 consumption with Pt addition indicates increased H-spillover, not enhanced CeO2 reducibility.
• H2-TPR can quantify dilute Pt nanocluster concentrations.

Conclusions:

• H2-TPR characteristics with Pt addition do not reflect increased CeO2 reducibility.
• H2-TPR primarily probes H-spillover kinetics and Pt nanocluster concentration.
• Caution is advised when directly linking H2-TPR to oxide reducibility; alternative material insights are possible.