Increasing Accessible Active Site Density of Non-Precious Metal Oxygen Reduction Reaction Catalysts through Ionic Liquid Modification

Abstract

Non-precious metal catalysts show great promise to replace the state-of-the-art Pt-based catalysts for catalyzing the oxygen reduction reaction (ORR), while their catalytic activity still needs to be greatly improved before their broad-based application. Here, we report a facile approach to improving the performance of zeolitic imidazolate framework-derived carbon (ZDC) toward the ORR by incorporating a small amount of ionic liquid (IL). The IL would preferentially fill the micropores of ZDC and greatly enhance the utilization of the active sites within the micropores, which are initially not accessible due to insufficient surface wetting. It is also disclosed that the ORR activity in terms of kinetic current at 0.85 V depends on the loading amount of the IL, and the maximum activity is obtained at a mass ratio of IL to ZDC at 1.2. The optimum stems from the counterbalance between the enhanced utilization of the active sites within the micropores and the retarded diffusion of the reactants within the IL phase due to its high viscosity.

Surface engineering for stable electrocatalysis

“…[179][180][181] Additionally, the presence of adsorbed *OH species above 0.5 V RHE can further accelerate atomic migration and agglomeration through a shuffling effect. 182 Notably, the start-up/shut-down procedures or fuel starvation in fuel cells can induce a cathodic potential excursion with a significant escalation in potential up to 1.5 V RHE , triggering the formation of an ultrathin oxide layer on the Pt surface. The subsequent reduction of this oxide layer at lower potentials leads to irreversible damage of the catalytic surface through an oxideplace exchange mechanism, leading to the degradation of electrocatalytic activity during the fuel cell operation.…”

“…179–181 Additionally, the presence of adsorbed *OH species above 0.5 V RHE can further accelerate atomic migration and agglomeration through a shuffling effect. 182…”

Enhancing Polymer Electrolyte Membrane Fuel Cells with Ionic Liquids: A Review

“…In this context, Zhang et al [60] present a straightforward technique for enhancing ORR performance of zeolitic imidazolate framework-derived carbon (ZDC) through the addition of a small amount of IL, as shown in Figure 7. It can be seen that the kinetics of the ORR were significantly improved.…”

Nitrogen‐Enriched Porous Carbon Materials from Expanded Polystyrene Waste for Oxygen Reduction Reaction and Rechargeable Zinc–Air Battery

“…The accessibility of the active sites within the micropores can also be enhanced by introducing an optimal amount of ionic liquids. [ 33 ] However, the approaches for obtaining the aforementioned characteristics for an optimal electrocatalyst are often tedious. Accordingly, it is of paramount importance to probe low‐priced, eco‐friendly materials to fabricate an effective electrocatalyst by facile synthetic procedure with the necessary properties for enhancing ORR performance.…”