Carbon supported Ag nanoparticles as high performance cathode catalyst for H2/O2 anion exchange membrane fuel cell

Abstract

A solution phase-based nanocapsule method was successfully developed to synthesize non-platinum metal catalyst—carbon supported Ag nanoparticles (Ag/C). XRD patterns and TEM image show Ag nanoparticles with a small average size (5.4 nm) and narrow size distribution (2–9 nm) are uniformly dispersed on the carbon black Vulcan XC-72 support. The intrinsic activity and pathway of oxygen reduction reaction (ORR) on the Ag/C and commercial Pt/C were investigated using rotating ring disk electrode (RRDE) tests at room temperature. The results confirmed that the 4-electron pathway of ORR proceeds on small Ag nanoparticles, and showed comparable ORR activities on the self-prepared Ag/C and a commercial Pt/C. A single H2-O2 anion exchange membrane fuel cell (AEMFC) with the Ag/C cathode catalyst exhibited an open circuit potential of 0.98 V and a peak power density of 190 mW/cm2 at 80°C.

Pt-free silver nanoalloy electrocatalysts for oxygen reduction reaction in alkaline media

“…Reaction order is one and the Tafel plots are also marked with great similarity with 2 distinct slope regions ( Figure 2). 20,56,61,[71][72][73][74][75] Experimental data supports the notion of similar reaction mechanism to that of Pt. However, unlike Pt which shows strong pH dependence at low overpotential, ORR on Ag shows no dependence on the pH.…”

“…The same group deposited these nanoparticles on Vulcan XC-72 and performed RRDE and Cyclic voltammetry (CV) to identify the ORR mechanism. 20 The calculated value of n for Ag/ XC-72 and Pt/C were 3.94 and 3.91 respectively. A comparison of the Tafel plots of Ag/XC-72 with Pt/C revealed 2 distinct regions.…”

“…The most significant advantage of ORR under alkaline conditions are the faster kinetics and lower overpotentials, potentially allowing use of inexpensive, platinum free metal catalysts such as silver and its alloys, doped carbons , transition metal oxides including spinels and perovskites and transition metal macromolecules like metal phthalocyanines for the reduction reaction at the cathode. [18][19][20][21][22][23] The shift of pH from 0 to 14 improves the ORR kinetics by decreasing the adsorption strength of anion species. 24 Surface independent electron transfers processes are active in alkaline media resulting in the more facile kinetics of ORR.…”

Hierarchical polybenzimidazole-grafted graphene hybrids as supports for Pt nanoparticle catalysts with excellent PEMFC performance

“…The average primary particle size of Pt/graphene is calculated to be about 3.5 nm with a wide size distribution ranging from 1 nm to 8 nm, as shown in Figure 3 (g, i). In sharp contrast, it is shown in Figure 3 after double-layer correction, [45,46] and is summarized in /g Pt , respectively. The higher surface area of Pt/PBI-XC72 over Pt/XC72 can be attributed to the smaller amount of agglomeration observed in TEM (Figure 3a and d), since the joined Pt nanoparticles will lose some active sites when participating in the reaction.…”

Nitrogen‐doped Carbon–CoOx Nanohybrids: A Precious Metal Free Cathode that Exceeds 1.0 W cm−2 Peak Power and 100 h Life in Anion‐Exchange Membrane Fuel Cells

“…First, the N‐C‐CoO x catalyst was able to achieve very high kinetic current in the operating AEMFC, 100 mA cm −2 at 0.85 V. This in‐cell kinetic behavior compares extremely well to the existing state‐of‐the‐art in both AEMFCs (Figure S10a) and PEMFCs (Figure S10c), even though many of the previous works were done at higher temperature (particularly PEMFC). Second, the N‐C‐CoO x cathode was able to achieve a mass transport limited current density of 3 A cm −2 and a maximum power density of 1.05 W cm −2 —both of which are the highest reported values for a PM‐free cathode in AEMFCs to date (Table S3, Figure S10b) . Such high power density and achievable current density shows that the reported catalyst, integrated with the ionomer, enabled the creation of catalyst layers that: i) have much lower mass transport resistance than previous PM‐free cathodes in operating AEMFCs; and ii) are competitive with PM‐free PEMFC cathodes.…”