Temporally-Resolved Ultrafast Hydrogen Adsorption and Evolution on Single Platinum Nanoparticles.

The hydrogen evolution reaction (HER) was studied on single platinum nanoparticles (NPs) using a microjet NP collision system. By ejecting NPs onto a closely-positioned ultramicroelectrode (UME), one can study single-particle collision electrochemistry in acid concentrations as high as 3 M, or 750 mM on the electrode surface. This is nearly two orders of magnitude greater than previously reported in NP-collision studies. The use of high-bandwidth recording and higher acid concentration allows us to temporally resolve the ultrafast hydrogen adsorption and evolution processes in HER on single colliding Pt NPs. Moreover, the electroactive surface area (EASA) and roughness factor (Rf) of single Pt NPs can be readily derived from the integrated hydrogen adsorption charge. The use of high acid concentrations is critical toward obtaining a full monolayer of adsorbed hydrogen before overlapping with the evolution process. This method allows one to study electrochemical and electrocatalytic behavior of metal NPs in a chemical environment that is close to that used in real applications, e.g. fuel cells and electrolyzers.