Hydrogen evolution at the buried interface between Pt thin films and silicon oxide nanomembranes

This paper reports the performance of hydrogen evolution reaction (HER) electrocatalysts based on Pt thin film electrodes that are encapsulated by silicon oxide (SiOx) nanomembranes. This membrane-coated electrocatalyst (MCEC) architecture offers a promising approach to enhancing electrocatalyst stability while incorporating advanced catalytic functionalities such as poison resistance and tunable reaction selectivity. Herein, a room temperature ultraviolet (UV) ozone synthesis process was used to systematically control the thickness of SiOx overlayers with nanoscale precision and evaluate their influence on the electrochemically active surface area (ECSA) and HER performance of the underlying Pt thin films. Through detailed characterization of the physical and electrochemical properties of the SiOx-encapsulated electrodes, it is shown that proton and H-2 transport occur primarily through the SiOx coating such that the HER takes place at the buried Pt vertical bar SiOx interface. Increasing the thickness of the SiOx overlayers results in monotonic increases in the overpotential losses of the MCEC electrodes. These overpotential losses were fit using a one-dimensional diffusion model, from which the H+ and H-2 permeabilities through SiOx were obtained. Importantly, the SiOx nanomembranes were found to exhibit high selectivity for proton and H2 transport in comparison to Cu2+, a model HER poison. Leveraging this property, we show that SiOx encapsulation can enable copper resistant operation of Pt HER electrocatalysts. It is expected that a more complete understanding of the structure property performance relationships of the SiOx overlayers will enable the design of stable MCECs capable of multifunctional catalysis with minimal loss in efficiency from concentration overpotential losses associated with mass transport through SiOx