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Updated: Sep 14, 2025

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Published on: April 12, 2019
Confirmation of the rate-determining step for ORR in the high potential region: adsorption process of oxygen
Jiaxi Zeng1, Jiyuan Lu1, LiLi Zhang1
1Shanghai Engineering Research Center of Hierarchical Nanomaterials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science & Technology, Shanghai 200237, China. jianghaibo@ecust.edu.cn.
Abstract:
The oxygen reduction reaction kinetics at low overpotentials (<15 mV vs. OCP) were investigated using PtNi and PtPb catalysts, revealing near-zero H+ (0.05-0.12) and first O2 (0.89-1.02) reaction orders, which conclusively identify O2 adsorption as the rate-determining step. Notably, PtNi demonstrated the lowest activation energy (21.81 kJ mol-1vs. 22.48 for Pt/C and 24.73 for PtPb), which was directly correlated with its narrower HOMO-LUMO gap (-1.02 eV). This reduced orbital energy spacing facilitates electron flow during the chemical adsorption process, destabilizing transition states and lowering activation barriers.
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