High Entropy Alloy (HEA) nanoparticles (NPs), consisting of more than five elements distributed throughout a single phase, are an emerging class of materials with a wide range of potential electrocatalytic applications. While promising, the complex structures of HEA materials make understanding their behavior difficult, as they can exhibit significant NP-to-NP variations in size, shape, and composition. Here, we present studies applying Targeted Electrochemical Cell Microscopy (TECCM) to probe electrocatalytic reactions occurring at individual HEA (CuNiCoFeMn) NPs synthesized, allowing precise relationships between NP size, shape, and elemental composition to be established. In TECCM, individual NPs are trapped within the meniscus of an electrolyte-filled pipet, allowing the electrocatalytic properties of individual NPs to be rigorously evaluated using traditional voltammetric techniques. By comparing these results to ex situ structural/elemental probes, electrocatalytic activity can be correlated with size, shape, and composition at the single NP level. These studies demonstrate single-entity electrochemical techniques such as TECCM open a new avenue for exploring the properties of heterogeneous HEA materials and rationally designing these materials for future applications.

Probing electrocatalytic reactions at individual high-entropy alloy nanoparticles using targeted electrochemical cell microscopy

ACS Spring 2022

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