Effective Strategy for Improving Electrocatalyst Durability by Adhesive Immobilization of Catalyst Nanoparticles on Graphitic Carbon Supports

We have found that Ta-based additive films in our catalyst system act as adhesives, which improves electrocatalyst durability by immobilizing the catalyst Pt NPs on the graphitic Vulcan carbon support. Furthermore, we suggest that this can be a general design principle in producing higher-durability electrocatalysts on graphitic supports. By electrochemically probing the contributing roles of the tantalum oxide (Ta2O5) and the polyphosphate (PPA) components in separate samples, we show that these combine to produce the observed improvement in activity and durability of our best catalyst, the tantalum polyphosphate (TaOPO4)-treated sample. To control variables for a valid electrochemical comparison, such as dissimilar catalyst particle size distributions and variations in surface coverage, four new catalyst samples closely matched in every way were prepared: (1) Pt/VC, (2) Pt/[PPA/VC], (3) Pt/[Ta2O5/VC], and (4) Pt­[TaOPO4/VC]. We present HR-TEM/HAADF-STEM, EDS elemental mapping, PXRD, XPS, and electrochemical activity and durability evidence, showing that the TaOPO4 and Ta2O5 additives act as adhesives, effectively tethering the NPs to the VC graphitic support surface. Pt/[Ta2O5/VC] exhibited 3× better durability as compared with the Pt/VC control because of better catalyst nanoparticle immobilization by the Ta2O5 adhesive. Pt­[TaOPO4/VC] is the overall best performer, exhibiting both a high MA of 0.82 A mgPt –1, the highest ORR MA after heat treatment, as well as 1.75× greater durability over the Pt/VC control.