Cobalt-Containing Nitrogen-Doped Carbon Materials Derived from Saccharides as Efficient Electrocatalysts for Oxygen Reduction Reaction

The development of non-precious metal electrocatalysts towards oxygen reduction reaction (ORR) is crucial for the commercialisation of polymer electrolyte fuel cells. In this work, cobalt-containing nitrogen-doped porous carbon materials were prepared by a pyrolysis of mixtures of saccharides, cobalt nitrate and dicyandiamide, which acts as a precursor for reactive carbon nitride template and a nitrogen source. The rotating disk electrode (RDE) experiments in 0.1 M KOH solution showed that the glucose-derived material with optimised cobalt content had excellent ORR activity, which was comparable to that of 20 wt % Pt/C catalyst. In addition, the catalyst exhibited high tolerance to methanol, good stability in short-time potential cycling test and low peroxide yield. The materials derived from xylan, xylose and cyclodextrin displayed similar activities, indicating that various saccharides can be used as inexpensive and sustainable precursors to synthesise active catalyst materials for anion exchange membrane fuel cells.

Effect of porosity and active area on the assessment of catalytic activity of non-precious metal electrocatalyst for oxygen reduction

We describe a method to study porous thin-films deposited onto rotating disc electrodes (RDE) applied to non-platinum group electrocatalyst obtained by pyrolysis of iron phthalocyanine and carbon, FePc/C. The electroactive area and porous properties of the thin film electrodes were obtained using electrochemical impedance spectroscopy under the framework of de Levie impedance model. The electrocatalytic activity of different electrodes was correlated to the total electroactive area (A_p) and the penetration ratio parameter through the film under ac current. The cylindrical pore model was extended to the RDE boundary conditions and derived in a Koutecky-Levich type expression that allowed to separate the effect of the electroactive area and structural properties. The resulting specific electrocatalytic activity of FePc/C heat treated at different temperatures was correlated to FePc surface concentration.

Transition-Metal- and Nitrogen-Doped Carbide-Derived Carbon/Carbon Nanotube Composites as Cathode Catalysts for Anion-Exchange Membrane Fuel Cells

Transition-metal- and nitrogen-codoped carbide-derived carbon/carbon nanotube composites (M-N-CDC/CNT) have been prepared, characterized, and used as cathode catalysts in anion-exchange membrane fuel cells (AEMFCs). As transition metals, cobalt, iron, and a combination of both have been investigated. Metal and nitrogen are doped through a simple high-temperature pyrolysis technique with 1,10-phenanthroline as the N precursor. The physicochemical characterization shows the success of metal and nitrogen doping as well as very similar morphologies and textural properties of all three composite materials. The initial assessment of the oxygen reduction reaction (ORR) activity, employing the rotating ring-disk electrode method, indicates that the M-N-CDC/CNT catalysts exhibit a very good electrocatalytic performance in alkaline media. We find that the formation of HO2 - species in the ORR catalysts depends on the specific metal composition (Co, Fe, or CoFe). All three materials show excellent stability with a negligible decline in their performance after 10000 consecutive potential cycles. The very good performance of the M-N-CDC/CNT catalyst materials is attributed to the presence of M-N x and pyridinic-N moieties as well as both micro- and mesoporous structures. Finally, the catalysts exhibit excellent performance in in situ tests in H2/O2 AEMFCs, with the CoFe-N-CDC/CNT reaching a current density close to 500 mA cm-2 at 0.75 V and a peak power density (P max) exceeding 1 W cm-2. Additional tests show that P max reaches 0.8 W cm-2 in an H2/CO2-free air system and that the CoFe-N-CDC/CNT material exhibits good stability under both AEMFC operating conditions.

Transition metal-containing nitrogen-doped nanocarbon catalysts derived from 5-methylresorcinol for anion exchange membrane fuel cell application

Highly active electrocatalysts for electrochemical oxygen reduction reaction (ORR) were prepared by high-temperature pyrolysis from 5-methylresorcinol, Co and/or Fe salts and dicyandiamide, which acts simultaneously as a precursor for reactive carbonitride template and a nitrogen source. The electrocatalytic activity of the catalysts for ORR in alkaline solution was studied using the rotating disc electrode (RDE) method. The bimetallic catalyst containing iron and cobalt (FeCoNC-at) showed excellent stability and remarkable ORR performance, comparable to that of commercial Pt/C (20 wt%). The superior activity was attributed to high surface metal and nitrogen contents. The FeCoNC-at catalyst was further tested in anion exchange membrane fuel cell (AEMFC) with poly-(hexamethyl-p-terphenylbenzimidazolium) (HMT-PMBI) membrane, where a high value of peak power density (P_max = 415 mW cm^-2) was achieved.

A post-synthesis surface reconstructed carbon aerogel as an enhanced oxygen reduction reaction catalyst for zinc–air batteries

After calcination and erosion, aerogel carbon materials have been subjected to surface reconstruction under the action of carbon fixation by iron at high temperature, resulting the change of specific surface area and ratio of surface species.

Polymer-derived Co/Ni–SiOC(N) ceramic electrocatalysts for oxygen reduction reaction in fuel cells

For the first time, the oxygen reduction reaction on transition metal and nitrogen doped SiOC-based electrocatalysts is studied.