Effect of loading level in platinum-dispersed carbon black electrocatalysts on oxygen reduction activity evaluated by rotating disk electrode

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

“…16,87 Films prepared using the NF-SIPAD technique (Pt/HSC and Pt/V) are extremely thin and uniform in the central region with almost no coffee ring as observed in the SEM images (Fig. S5, SI).…”

“…Additionally, a discrete Nafion film >0.2 μm (for an O 2 diffusion boundary layer in the electrolyte δ d ∼15 μm, 1600 rpm) present over the catalyst layer introduces an O 2 diffusion resistance proportional to 1/i f to attenuate the limiting current. 15,16 The limiting currents for Pt/HSC and Pt/V catalyst layers show no discernible trend (Pt/HSC: 5.8 ± 0.2 mA/cm 2 , n = 155; Pt/V: 5.9 ± 0.1 mA/cm 2 , n = 111) or dependence on fabrication technique within the limits of error. The limiting currents for Pt/HSC and Pt/V are comparable to that for a poly-Pt (6.06 ± 0.02 mA/cm 2 Effect of I/C ratio and loading.-We conducted RDE experiments using inks having various I/C ratios in the range 0-30; a precipitous loss in the ECA was observed (not shown) only at excessive I/C ratios ∼30, with 80% loss for N-SAD and 60% loss for N-RAD techniques; no noticeable losses were observable at lower ionomer contents within experimental error.…”

“…Additionally, the literature does not offer adequate descriptions of the admittedly non-trivial measurement of the thickness and uniformity of the catalyst layer itself until very recently. 17 Nevertheless, the refinement and advanced implementation of the TF-RDE technique reported by the groups discussed so far 6,[13][14][15][16] has had a profound influence in the field of electrocatalyst characterization leading to its widespread adoption. TF-RDE has been use to determine the ORR activity of Pt-alloy catalysts, [18][19][20][21][22][23][24][25][26] core-shell catalysts, [27][28][29][30][31][32] extended thin film structures, [19][20][21]33,34 non-precious metal catalysts, [35][36][37][38][39][40][41] Pt on alternative supports, 42,43 as well as particle size effects, 14,17,[44][45][46][47][48][49][50] oxygen reaction order, 15,…”

“…Previous ionomer cap studies have predominantly addressed O 2 diffusion within the Nafion cap and the need to minimize the cap thickness to directly obtain kinetic values from the basic K-L expression without incorporation of the additional term (1/i f ) corresponding to film resistance. Although it is a wellestablished fact that a calculated Nafion cap thickness <0.1-0.2 μm has no measurable effect on the O 2 limiting current, 15,16 it does not imply that the ionomer impact on ORR kinetics can be disregarded.…”

Oxygen Reduction Reaction Activity and Durability of Pt Catalysts Supported on Titanium Carbide

“…A thin film of Nafion was coated on the catalyst layer with an average thickness of 0.05 μm [39]. The use of such a thin catalyst layer with a thin Nafion film enables us to evaluate a "real" kinetically-controlled activity of the catalyst for the ORR [47].…”