Adsorbate interactions on surface lead to a flattened Sabatier volcano plot in reduction of oxygen

• Published in: Journal of catalysis 2012-11, Vol.295, p.59-69
• Main Authors: Qi, Liang, Li, Ju
• Format: Article
• Language: English
• Subjects: activation energy; Adsorbate interactions; Adsorbents; adsorption; Catalysis; Catalysts; catalytic activity; Chemistry; electrochemistry; Exact sciences and technology; First-principles calculations; General and physical chemistry; Microkinetic model; Oxygen; Oxygen Reduction; Reaction kinetics; Sabatier principle; Sensitivity; Surface Catalysis; Surface chemistry; surface interactions; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Volcano Plot
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2012.07.019

(a) Interactions between adsorbates flatten the volcano plot of catalytic activity vs. adsorption strength and reduce sensitivity to material energetics from Arrhenius-law expectation; the interactions of different adsorbates may also shift volcano peak position. (b) Considering these interactions, a microkinetic model of oxygen reduction reaction based on first-principle calculations can show flattened volcano plot, in agreement with experimental sensitivity behavior. Out model and analyses provide a systematic method to quantitatively investigate sensitivities of surface reactions when mean-field approximation is reasonable. [Display omitted] ► We propose a microkinetic model of oxygen reduction with adsorbate interactions. ► It outputs similar steady-state reaction rates on Pt (111) and (100) surfaces. ► It explains why surfaces with different adsorption strengths have similar activities. ► Adsorbate interactions reduce sensitivities of activities to material energetics. ► It provides a systematic method to quantitatively investigate sensitivities of surface reactions when mean-field approximation is reasonable. Ab initio electronic-structure calculations of surface catalysis often give changes ⩾0.1eV for activation energies of intermediate steps when the surface structure or composition is varied, yet ⩾50-fold change in activity according to naive interpretation of the Arrhenius formula is usually not seen in corresponding experiments. To quantitatively analyze this sensitivity inconsistency between simulations and experiments, we propose a mean-field microkinetic model of electrochemical oxygen reduction reaction on Pt (111) and (100) surfaces, which outputs similar steady-state reaction rates despite of large differences in adsorption energies of reaction intermediates and activation energies. Sensitivity analyses indicate lateral repulsions between surface adsorbates (“enthalpic effect”) and site competition (“entropic effect”) flatten the catalytic activity vs. adsorption strength volcano plot and reduce sensitivity to material elementary energetics, in agreement with the observed experimental sensitivity behavior. Our analyses provide a systematic method to quantitatively investigate sensitivities of surface reactions when the mean-field approximation is reasonable.