Accelerating Oxygen‐Reduction Catalysts through Preventing Poisoning with Non‐Reactive Species by Using Hydrophobic Ionic Liquids

Abstract

Developing cost-effective electrocatalysts for the oxygen reduction reaction (ORR) is a prerequisite for broad market penetration of low-temperature fuel cells. A major barrier stems from the poisoning of surface sites by nonreactive oxygenated species and the sluggish ORR kinetics on the Pt catalysts. Herein we report a facile approach to accelerating ORR kinetics by using a hydrophobic ionic liquid (IL), which protects Pt sites from surface oxidation, making the IL-modified Pt intrinsically more active than its unmodified counterpart. The mass activity of the catalyst is increased by three times to 1.01 A mg(-1) Pt @0.9 V, representing a new record for pure Pt catalysts. The enhanced performance of the IL-modified catalyst can be stabilized after 30 000 cycles. We anticipate these results will form the basis for an unprecedented perspective in the development of high-performing electrocatalysts for fuel-cell applications.

Platinum Nanoparticles Modified with Perfluorinated Alkylamines as a Model Cathode Catalyst for Fuel Cells

“…These tailored materials have also been applied to oxygen and glucose sensors . Recently, coating metal NPs using ionic liquid or coating a support with polymer has been used as a novel approach to fabricate high‐performance electrocatalysts. Nafion ® and perfluorosulfonic acid (PFSA) have also been used as coating materials for metal NPs or the catalyst itself , since Nafion ® is used as a binder for the catalyst layer.…”

“…Adsorption of a hydroxyl group on Pt during an anodic scan starts above 0.6 V for the Pt catalyst and bulk Pt . These nonreactive oxygenated species usually suppress the ORR kinetics by covering the Pt active sites . Close inspection of the CV above 0.5 V reveals that the onset potential of adsorption of the hydroxyl group is in the order 30 % Pt/CB<OA‐Pt/CB≈OA/UFHA‐Pt/CB (Fig.…”

“…The intrinsic Tafel slope on clean Pt is −120 mV dec −1 , which can be observed at low potentials, and the deviation from this value at high potentials (V>0.85 V) is ascribed to the adsorption of oxygenated species on the Pt surface . The change in the Tafel slope can be used as an indicator of the changes in the coverage of oxygenated species on Pt . The 30 % Pt/CB has a Tafel slope of −63.7 mV dec −1 , similar to the previously reported commercial Pt catalysts , while OA/UFHA‐Pt/CB and OA‐Pt/CB have slopes of −76.4 and −73.8 mV dec −1 , respectively.…”

Engineering the Interface of Carbon Electrocatalysts at the Triple Point for Enhanced Oxygen Reduction Reaction

“…[26] In 2017, Walsh et al investigated the synthesis of protic ionic liquids with high ion conductivity. [55] Our group has recentlyr eported an ovel application of IL coatings onto carbon based non-precious electrocatalyst. Yetm any advantages of ionic liquids, such as large electrochemical window,g ood thermal stability,a nd solubility of ad iverse range of organic and inorganic compounds are rarely fully used in this field.…”

“…[54] In the year 2010, ILs have been first applied to Pt-based electrocatalyst and proved to contributet ot he oxygen utility on active sites and promote the ORR reaction. [55] Our group has recentlyr eported an ovel application of IL coatings onto carbon based non-precious electrocatalyst. Despite having ad ifferent interaction mechanism between IL and the carbon catalyst comparedw ith Pt, the improvementofc atalytic activity of non-metal carbons resulted from the fact that the IL provides an optimized triple-phase point for the ORR reaction by providing reasonable hydrophobicity and oxygen affinity.…”