(705b) Enhancing the Durability of Electrocatalysts Using Ultrathin Silica Layers

For the energy transition of the chemical industry, extending the lifetime of electrocatalytic materials is a major challenge. Here, we employ atomic layer deposition (ALD, a cyclic gas phase coating process) to coat the surface of carbon black supported metal nanoparticles with an ultrathin layer of silicon dioxide (SiO₂) to prevent degradation of the catalyst. We will illustrate this approach with two examples:

1. protecting platinum nanoparticles for the hydrogen evolution reaction against detachment and aggregation;
2. protecting silver nanoparticles for conversion of CO₂ into CO against SO₂ impurities in the feed stream.

For example 1, we studied the current density before and after an accelerated durability test (ADT) at −0.2 V versus reversible hydrogen electrode (RHE) in an H-cell setup. The current density of the unprotected catalyst was reduced by 34%. By contrast, for the catalyst protected with 2 SiO₂ ALD cycles, the current density was reduced by just 7%, whereas for 5 SiO₂ ALD cycles, the current density was reduced by only 2%. The coating led to a factor five decrease in the Pt concentration in the electrolyte after the ADT.

For example 2, we studied the effect of SO₂ impurities (various concentrations, up to 1000 ppm) in the CO₂ feed to an H-cell setup, operated at various potentials. We observed that the silver catalyst stayed stable for 20 hours when fed with pure CO₂. However, after only 1 hour of operation with 1000 ppm SO₂ added, the faradaic efficiency for CO already dropped from 70% to 46% at −1.0V versus RHE. For catalysts protected with 4 or 8 ALD cycles SiO₂, the faradaic efficiency remained relatively constant. This is likely due to the SO₂ and CO₂ permeating differently through the nanocoatings.

Both examples clearly show the strength of applying nanocoating on electrocatalysts using ALD to extend their lifetime.