Clarifying sequential electron-transfer steps in single-nanoparticle electrochemical process for identifying the intrinsic activity of electrocatalyst
Single-nanoparticle collision electrochemistry(SNCE)is an effective method for determining the intrinsic activity of electrocatalysts at the single-nanoparticle(NP)level.Despite fruitful advance-ments in the SNCE field,determining a quantitative relationship between the NP structure and its activity has remained difficult because of an unclear understanding of SNCE.In this study,we suc-cessfully uncovered the essential roles of the sequential electron-transfer steps in the SNCE system in regulating the apparent electrocatalytic activity of single NPs.By monitoring the oxygen reduc-tion reaction of individual Pt NPs,significantly distinct apparent activities were observed at differ-ent electrodes owing to the rate-determining step-controlled electron transfer process.Further-more,a new theoretical model is proposed for treating the electrochemical current,which involves NP-electrode electron transfer,heterogeneous electron transfer,and mass transfer in solution as sequential steps in the SNCE system.The combination of theoretical simulations and high-resolution electrochemical measurements allows for the corresponding parameters(contact resistance,heterogeneous kinetic constants,and adsorption possibility)of sequential elec-tron-transfer steps to be quantified,resulting in the identification of a rate-determining step for improving the intrinsic activity of electrocatalysts.This work provides a clear picture for determin-ing the intrinsic activity of single NPs in SNCE measurements and introduces a new conceptual route for the quantification of structure-activity relationships,which ultimately guide the rational design and optimization of electrocatalytic nanomaterials.
Single nanoparticleElectrocatalystElectron transferRate-determining stepIntrinsic activity
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