Hydrogen Evolution at the Buried Interface between Pt Thin Films and Silicon Oxide Nanomembranes

Abstract

This paper reports the performance of hydrogen evolution reaction (HER) electrocatalysts based on Pt thin film electrodes that are encapsulated by silicon oxide (SiO x ) 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 roomtemperature ultraviolet (UV) ozone synthesis process was used to systematically control the thickness of SiO x 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 SiO x -encapsulated electrodes, it is shown that proton and H 2 transport occur primarily through the SiO x coating such that the HER takes place at the buried Pt|SiO x interface. Increasing the thickness of the SiO x 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 SiO x were obtained. Importantly, the SiO x nanomembranes were found to exhibit high selectivity for proton and H 2 transport in comparison to Cu 2+ , a model HER poison. Leveraging this property, we show that SiO x encapsulation can enable copperresistant operation of Pt HER electrocatalysts. It is expected that a more complete understanding of the structure−property− performance relationships of the SiO x 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 SiO x .

Ultrathin Amorphous Silica Membrane Enhances Proton Transfer across Solid‐to‐Solid Interfaces of Stacked Metal Oxide Nanolayers while Blocking Oxygen

“…Using a planar Pt film (100 nm) on Si wafer support as electrode and as reflective surface for infrared probing, Pt‐H absorbance growth via H under‐potential deposition (H + + Pt → Pt‐H, commonly referred to as H upd ) was observed by FT‐IRRAS. H + flux through single SiO 2 , Co 3 O 4 , and TiO 2 nanolayers, and multiple stacked layers (cartoon Figure S1, Supporting Information) was quantitatively monitored by EIS, while O 2 permeation behavior was characterized by CV.…”

“…Proton transport and gas permeability properties based on cyclic voltammetry (CV) measurements have recently been reported for single oxide nanolayers such as ultrathin silica prepared by atomic layer deposition (ALD) or ozone treatment of spin‐cast Si precursor, or for chromia nanolayers prepared by solution‐based photo‐ or electrodeposition methods . However, the development of functional nanoscale systems typically requires integration of ultrathin structures with higher degree of complexity.…”

A Stand‐Alone Module for Solar‐Driven H2 Production Coupled with Redox‐Mediated Sulfide Remediation

“…The stability of the permselective layer is a remaining problem that is caused by the redox reaction forming a soluble metal complex. To overcome this issue, a redox inactive layer could be a promising candidate, such as SiO x and TiO x . Optimization of the layers’ thickness and pore size on a desired substrate is required to prevent the diffusion of the redox ions while allowing protons and H 2 to go through.…”

“…A crossover could take place on the cathode, where the oxidized Fe 3+ ‐HEDTA ion can be reduced instead of the HER. To avoid the crossover, a nano‐membrane coating was applied on the HER catalyst (bottom image in Figure ), which prevents the diffusion of large redox ions from reaching the electrocatalyst underneath while allowing protons and hydrogen to go through . In this study, CrO x was employed as a model nano‐membrane layer for the ion‐exchange‐membrane‐free device because of its well‐known functionality in corrosion protection, photocatalytic water splitting, and electrochemical chlorate production .…”

Sustainable Membrane‐Coated Electrodes for CO2 Electroreduction to Methanol in Alkaline Media

“…[4,27] Also, high alkaline pH has been observed to influence CO 2 reduction on Cu catalyst surfaces, due to the hydroxide ions role in modulating the catalyst surface and suppressing the HER. Protective membrane layers composed of metal oxides [39,40] have been proposed for HER and Methanol Oxidation Reaction, and conductive polymers [41][42][43][44][45] have been studied for the CO 2 electroreduction at chemistry laboratories, where the polymer both protects the catalytic layer and boosts the ion transport to the active sites, thus reducing the required over potentials [42,46] and slightly improving the efficiency of the CO 2 electrochemical reduction in different media. In CO 2 electrolyzers working in alkaline conditions, OH À ions rapidly react in the presence of CO 2 to form HCO 3 À and CO 3 2À but the lower mobility of the latter ions compared to OH À usually inhibit ion transport and reduce CO 2 reduction efficiency.…”