Indispensable Nafion Ionomer for High-Efficiency and Stable Oxygen Evolution Reaction in Alkaline Media

Abstract

Addressing the challenge of sluggish kinetics and limited stability in alkaline oxygen evolution reactions, recent exploration of novel electrochemical catalysts offers improved prospects. To expedite the assessment of these catalysts, a half-cell rotating disk electrode is often favored for its simplicity. However, the actual catalyst performance strongly depends on the fabricated catalyst layers, which encounter mass transport overpotentials. We systematically investigate the role and sequence of electrode drop-casting methods onto a glassy carbon electrode regarding the efficiency of the oxygen evolution reaction. The catalyst layer without Nafion experiences nearly 50% activity loss post stability test, while those with Nafion exhibit less than 5% activity loss. Additionally, the sequence of application of the catalyst and Nafion also shows a significant effect on catalyst stability. The catalyst activity increases by roughly 20% after the stability test when the catalyst layer is coated first with an ionomer layer, followed by drop-casting the catalysts. Based on the half-cell results, the Nafion ionomer not only acts as a binder in the catalyst layer but also enhances the interfacial interaction between the catalyst and electrolyte, promoting performance and stability. This study provides new insights into the efficient and accurate evaluation of electrocatalyst performance and stability as well as the role of Nafion ionomer in the catalyst layer.

Challenges and progress in oxygen evolution reaction catalyst development for seawater electrolysis for hydrogen production

“…109 Naon acts as an effective binder and further improves the interfacial interaction between electrolyte and catalyst, improving stability and performance by up to 20% compared to Naon-free catalyst layers. 110 Lan et al synthesised a Mo-doped Ni 3 S 2 nanocluster array applied to NF (Mo-Ni 3 S 2 /NF), where the catalyst is prepared using a single-step modied solvothermal methodology using thiourea as the sulphur source at 160 °C for 6 hours. 106 The introduction of Mo progresses the nickel and S organisation, improving electronic interactions and increasing OER reaction kinetics and long-term stability, according to the authors.…”

Simple Preparation and Characterization of Hybrid Cobalt Phthalocyanine on Multiwalled Carbon Nanotube Electrodes

“…Recent works from Zhang et al and Boutin et al have shown that cobalt phthalocyanine (CoPc) supported on multiwalled-carbon nanotubes (MWCNT) is an excellent hybrid electrode for CO 2 reduction. , In these articles, the researchers used Nafion, a branched fluoropolymer ionomer with pendent terminal sulfonate groups, as a binding agent to keep the MWCNT and CoPc from delaminating from the electrode by providing mechanical strength. ,,− Also, ionomers like Nafion are commonly used in the fuel cell field as dispersants stabilizing catalyst inks . At low loadings, ionomers have been shown to be beneficial to the electrode by providing a higher ionic conductivity, and a degree of control of wettability and aggregate size. − At high ionomer loadings >30 wt %, there can be negative consequences such as capacitive charging, and a decrease in reactant mass transport to the catalyst. , The introduction of these ionomers will also inherently alter the microenvironment of the catalyst site as addition of Nafion has been found to affect local pH and local structural morphology changes via solvent dependence. , Sharma et al observed in their CO 2 reduction system a decrease in CO selectivity and active catalyst as Nafion loading increased up to 30 wt % . Of particular interest is the nature of interaction between the immobilized catalysts and their graphitic supports .…”

Self-assembled monolayers for electrostatic electrocatalysis and enhanced electrode stability in thermogalvanic cells

“…1(b) displays this scenario for a hypothetical carbon nanomaterial decorated with a precious metal nanoparticles, and dropcast with Nafion ionomer to serve as a physical binder to improve the dispersion and stability of the layer. 19 …”