Advancing Insights into Electrochemical Pre‐Treatments of Supported Nanoparticle Electrocatalysts by Combining a Design of Experiments Strategy with In Situ Characterization

Abstract Activation, break‐in, and/or pre‐treatment protocols are generally applied to energy conversion devices before regular operation to reach stable performance. There remains much to understand about the relationships among physical properties, performance, and electrochemical pre‐treatments. Here, a design‐of‐experiments (DoE) strategy is employed to address this gap by demonstrating the influence of five pre‐treatment parameters for carbon‐supported Pt‐nanoparticle catalysts on the electrocatalytic oxygen reduction reaction (ORR). A subset of pre‐treatments, developed using a central composite design, are tested in a flow cell combined with an inductively‐coupled plasma mass spectrometer (on‐line ICP‐MS). The DoE‐based approach facilitates comprehensive insights from two orders of magnitude fewer experiments than a conventional grid search. The coupled on‐line ICP‐MS setup enables effective catalysis and real‐time catalyst dissolution data. Leveraging insights from DoE for on‐line ICP‐MS and additional characterization, a model is built between the degradation of a multi‐dimensional supported Pt surface, its performance, and applied electrochemical parameters. These investigations identify surface modifications, such as oxidation, and subsequent restructuring of Pt during pre‐treatment as a primary cause of performance deterioration during ORR. By combining DoE with advanced characterization techniques, a powerful approach is demonstrated to gain a mechanistic understanding of pre‐treatment protocols that can be broadly adapted to various reaction chemistries.