High-temperature pyrolyzed FeN(x)/C catalyst is one of the most promising nonprecious metal electrocatalysts for oxygen reduction reaction (ORR). However, it suffers from two challenging problems: insufficient ORR activity and unclear active site structure. Herein, we report a FeN(x)/C catalyst derived from poly-m-phenylenediamine (PmPDA-FeN(x)/C) that possesses high ORR activity (11.5 A g(-1) at 0.80 V vs RHE) and low H2O2 yield (<1%) in acid medium. The PmPDA-FeN(x)/C also exhibits high catalytic activity for both reduction and oxidation of H2O2. We further find that the ORR activity of PmPDA-FeN(x)/C is not sensitive to CO and NO(x) but can be suppressed significantly by halide ions (e.g., Cl(-), F(-), and Br(-)) and low valence state sulfur-containing species (e.g., SCN(-), SO2, and H2S). This result reveals that the active sites of the FeN(x)/C catalyst contains Fe element (mainly as Fe(III) at high potentials) in acid medium.

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Fe/N/C is a promising non-Pt electrocatalyst for the oxygen reduction reaction (ORR), but its catalytic activity is considerably inferior to that of Pt in acidic medium, the environment of polymer electrolyte membrane fuel cells (PEMFCs). An improved Fe/N/C catalyst (denoted as Fe/N/C-SCN) derived from Fe(SCN)3, poly-m-phenylenediamine, and carbon black is presented. The advantage of using Fe(SCN)3 as iron source is that the obtained catalyst has a high level of S doping and high surface area, and thus exhibits excellent ORR activity (23 A g(-1) at 0.80 V) in 0.1 M H2SO4 solution. When the Fe/N/C-SCN was applied in a PEMFC as cathode catalyst, the maximal power density could exceed 1 W cm(-2).

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A 40 wt% Pt/C cathode electrocatalyst with controlled Pt particle size of ~2.9 nm showing better performance than commercial catalyst for direct methanol fuel cell was prepared by a polyol process with water but without using stabilizing agent.Pt-based electrocatalysts with high loading are usually employed in direct methanol fuel cells (DMFC) as cathode electrocatalysts for oxygen reduction reaction at relatively low temperature. Synthesis of highly dispersed supported platinum with uniform nanoparticle size still remains a challenge, especially for high metal loading. The conventional methods for the synthesis of Pt and Pt alloy electrocatalysts are mainly impregnation 1 and colloid methods such as sulfite-complex route 2 and NR 4+ -stabilized metal colloids route. 3 The impregnation is limited because the average particle size is usually large and the size distribution is broad. Both colloidal routes produced well-homogenized ultrafine Pt electrocatalysts, but the complexity of these synthesis hinders its utilization. 4 Many investigators have contributed much endeavour to search for alternative routes. 5 In this paper, uniform platinum nanoparticles with an average diameter of about 2.9 nm supported on carbon with Pt loading up to 40 wt% were prepared by a modified polyol process. The modified polyol method exhibits the merits of impregnation and colloid procedures, i.e., the preparation method is simple but it is able to control the particle size and distribution. The as-synthesized Pt/C electrocatalyst shows better electrocatalytic activity for oxygen reduction reaction in DMFC than that of the commercial catalyst.The precursor, chloroplatinic acid, was dissolved into ethylene glycol (EG) and mixed with carbon black (Vulcan XC-72R, Cabot Corp., S BET = 236.8 m 2 g 21 ) suspended in distilled water. The mixture was maintained at 403 K in an oil bath for 3 h to ensure the complete reduction of Pt. A flow of argon was passed through the reaction system to remove oxygen and organic by-products. In the course of reaction, the evolved vapour was trapped and collected for GC-MS analysis. The resulting solid was filtered, washed with copious distilled water and dried at 343 K in vacuo. The obtained sample was denoted as 40 wt% Pt/C-EG. † The obtained electrocatalyst contains no stabilizing agent. This feature makes the modified process unique, because applications of the traditional polyol process 6 based on stabilizer such as polyvinyl pyrrolidone (PVP) were restricted in the area of electrocatalysis due to serious agglomeration of metal particles after removing the surfactant at relatively high temperature. Besides, the modified polyol process is carried out in a EG/H 2 O mixed solution, whereas, for the conventional polyol process, a strictly anhydrous organic solution is required. 6 The 40 wt% Pt/C-EG and the commercial 40 wt% Pt/C (Johnson Matthey Corp., denoted as 40 wt% Pt/C-JM) were comparatively tested as cathode electrocatalyst in DMFC. Fig. 1a shows the TEM image of the 40% Pt/C-EG sample. As the image ...

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