Silver Oxygen Reduction Electrocatalyst in Alkaline Medium: Aging and Protective Coating

Abstract

The oxygen reduction reaction (ORR) is a key process in anion exchange membrane fuel cells. The alkaline conditions should allow silver‐based cost‐efficient catalysts to replace platinum group metal materials. However, Ag electrochemical stability or lack of stability in alkaline medium is still to be demonstrated. Herein, Ag catalyst nanoparticles (NPs) are characterized by identical location transmission electron microscopy and X‐ray photoelectron spectroscopy after electrochemical cycling, revealing the losses of activity and surface. Herein, a facile method for enhancing the chemical stability of Ag catalysts in an alkaline environment by depositing a protective polydopamine (PDA) coating is reported. It is enhanced via crosslinking with polyethyleneimine (PEI), on the surface of Ag NPs. The enhanced electrochemical stability of Ag PDA–PEI nanocatalyst via the analysis of ORR polarization curves during accelerated stress test cycling is demonstrated, with at least one order of magnitude higher durability than the standard Pt/C catalyst. Moreover, electrochemical measurements indicate that the protective PDA–PEI coating has good permeability to O2, with a positive effect on the ORR activity of Ag NPs.

Surface Plasmon Resonance Modulation by Complexation of Platinum on the Surface of Silver Nanocubes

“…45−47 The PDA coating can prevent leaching in the aqueous environment. 44 In addition, a thin layer of PDA on Ag NCs improves the sensing of biological molecules through π−π interactions and hydrogen bonds. 14 In our r e s e a r c h , t h e P D A c o a t i n g w a s d o p e d w i t h hexachloroplatinate(IV) complexes at varying concentrations.…”

“…For this, plasmonic metal core dielectric shells were synthesized. Silver NC (and NW) cores were coated with the polydopamine (PDA) nanometric shell using a technique developed in our laboratory, and we adapted it to differently sized silver NCs with different thickness coatings. PDA is a final oxidation product of dopamine-HCl or other catecholamines .…”

“…That material is widely adopted in science and the chemical industry due to its simplicity, low cost, and adaptability to a variety of scientific and applicative components. PDA has a unique ability to create a uniform and conformal thin layer by a simple coating process. − The PDA coating can prevent leaching in the aqueous environment . In addition, a thin layer of PDA on Ag NCs improves the sensing of biological molecules through π–π interactions and hydrogen bonds .…”

The Role of Steps on Silver Nanoparticles in Electrocatalytic Oxygen Reduction

“…Silver is a potential alternative electrocatalyst for hydrogen fuel cells. This is because Ag has similar properties to Pt [13][14][15]. In addition, Ag-based catalysts are 50 times cheaper than the industrial Pt/C standard [14].…”

“…This is because Ag has similar properties to Pt [13][14][15]. In addition, Ag-based catalysts are 50 times cheaper than the industrial Pt/C standard [14]. Previous studies have revealed that Ag nanowires, nanocubes, and nanoparticles have high catalytic performance due to their unique surface morphology [16].…”