Effect of Preparation Conditions of Sol–Gel-Derived Co–N–C-Based Catalysts on ORR Activity in Acidic Solutions

Abstract

Using a Co oxide ethanol-based sol as a precursor solution, nitrogen ͑N͒-and carbon ͑C͒-containing ligands ͓1,2 phenylene diamine ͑phen͒ and ethylene diamine ͑en͔͒ were added to produce an oxygen reduction reaction ͑ORR͒ catalyst precursor. After adsorption on carbon powder, heat-treatment in an inert atmosphere at 500-900°C, and the addition of Nafion as a binder, the powdered mixture was coated on a glassy carbon electrode and evaluated for its ORR activity in 0.5 M H 2 SO 4 . The catalystcarbon powder ratio, heat-treatment temperature, ligand type, and ligand:Co ratio were optimized, and the effect of increased catalyst layer thickness, particle size, and C support was also determined. It was concluded that a phen-based catalyst with a metal to ligand ratio of 1:2, a heat-treatment at 900°C, and a concentration of 4 wt % Co was the most active, selective, and stable ORR catalyst material of the materials developed in the present work. X-ray photoelectron spectroscopy and X-ray diffraction analysis showed the formation of both Co metal and CoN 4 units upon heat-treatment, with the most active catalyst having a 5.3:1 overall N-Co ratio.

Pt/Carbon Catalyst Layer Microstructural Effects on Measured and Predicted Tafel Slopes for the Oxygen Reduction Reaction

“…Earlier porous electrode theory developed by de Levie 12 provides a means of generating Tafel plots (and Tafel slope values) assuming the presence of a migration (ohmic)-induced potential distribution in a single pore and using a reasonable estimate of the four porous film properties, L, r, κ, and i o . Therefore, our goal was to determine if the predicted Tafel slopes would change in the same way and to the same extent as seen in our experimental data (e.g., Figures 3,5,10) when the film properties were altered, while keeping all other reaction conditions fixed. However, in the present work, the exact value of only one parameter, κ, the bulk solution conductivity, is known with certainty, and it is assumed to be the same as the pore solution conductivity.…”

Iron and Copper Containing Oxygen Reduction Catalysts From Templated Glucose–Histidine

“…Among various materials, nitrogen modified carbons also containing non-precious transition metals (Fe and Co) are considered interesting because of their ORR activity and reliability as confirmed by results from independent groups [5][6][7][8][9][10][11][12][13][14][15]. Several preparative methods are reported: 1) carbon impregnation with metal organosalts or cyanoderivatives, followed by thermal activation in the presence of e.g.…”

Tuning the Process Gas in a Dual Plasma Process to Enhance the Performance of Cobalt-Polypyrrole Catalyts for the Oxygen Reduction Reaction in Fuel Cells

“…(32) With sol-gel-derived Co:N:C-based catalysts, values up to 0.58 V have been achieved. (18) stability of the compounds The decrease of V PR in percent is presented in figure 4(c). For comparison, the same measurement done with a commercially available platinum catalyst (20 wt.-% platinum on Vulcan XC72R) is also displayed.…”