Electrochemical Heterogeneity at the Nanoscale: Diffusion to Partially Active Nanocubes

Area of Science:

• Computational electrochemistry
• Nanomaterials science
• Electrocatalysis

Background:

• Understanding the structure-activity relationship is crucial for developing new electrocatalytic materials.
• Heterogeneity in nanoparticle activity presents a significant challenge in theoretical studies.
• Accurate theoretical analysis previously required complex 3D electrochemical simulations.

Purpose of the Study:

• To investigate how varying the number of active faces on a nanoparticle cube affects its diffusion-limited flux.
• To explore the impact of non-independent diffusion between nanoparticle faces on overall activity.
• To provide insights into the limitations of correlation-based approaches in nanoscale activity measurements.

Main Methods:

• Utilized three-dimensional electrochemical simulations to model diffusion-limited flux.
• Analyzed the flux to a cubic nanoparticle with a variable number of active faces.
• Examined the diffusional interactions between adjacent active and inactive faces.

Main Results:

• The diffusion-limited flux to the nanoparticle cube is not linearly proportional to the total active surface area.
• Faces of the cube exhibit interdependent diffusion, where the activity of one face influences the flux to neighboring faces.
• This diffusional coupling leads to deviations from linear scaling of flux with active area.

Conclusions:

• Nanoparticle activity is significantly influenced by the spatial distribution of active sites, not just the total area.
• The assumption of diffusional independence is invalid for understanding flux in heterogeneous nanoparticles.
• Experimental methods correlating activity with surface area need to account for these complex diffusional effects at the nanoscale.