Iron-/Nitrogen-Doped Electrocatalytically Active Carbons for the Oxygen Reduction Reaction with Low Amounts of Cobalt

The Oxygen Reduction Activity of Nitrogen-doped Graphene

Graphite nitrogen, pyridine nitrogen and pyrrole nitrogen are the main nitrogen types in nitrogen-doped graphene materials. In order to investigate the mechanism of the oxygen reduction activity of nitrogen-doped graphene, several models of nitrogen-doped graphene with different nitrogen contents and different nitrogen types are developed. The nitrogen content is varied from 1.3 at% to 7.8 at%, and the adsorption energy is calculated according to the established models, then the band gaps are analyzed through the optimization results, so as to compare the magnitude of the conductivity. Finally, the oxygen reduction activity of graphite nitrogen-doped graphene (GNG) is found to be better than pyridine nitrogen-doped graphene (PDNG) and pyrrole nitrogen-doped graphene (PLNG) when the nitrogen content is lower than 2.6 at%, and the oxygen reduction activity of PDNG is the best when the nitrogen content was higher than 2.6 at%.

Electrospun nanofibers modified with zeolitic imidazolate framework-8 for electrochemiluminescent determination of terbutaline

For the first time it is demonstrated that zeolitic imidazolate framework-8 electrospun nanofibers (ZIF-8 NF) could serve as electrochemiluminescence (ECL) accelerator for the facile detection of terbutaline residual. A novel ECL sensor for the determination of terbutaline was fabricated based on ZIF-8 NF. The ZIF-8 NF were successfully prepared according to electrospinning and in-situ growth method. First, chitosan was modified on the surface of the electrode, and then the ZIF-8 NF was modified onto the upper layer of the chitosan. Taking advantages of chitosan and ZIF-8 NF in conductivity and electrocatalysis, the modified electrode presents obvious ECL phenomenon in 0.2 M PBS solution (pH 10.0) containing 0.025 M luminol. After the addition of terbutaline, ECL intensity decreased significantly, and the decreasing value showed a linear relationship with the logarithm of terbutaline concentration. The linear range was from 2.0 × 10^-10 to 2.0 × 10^-5 M, and the detection limit was 1.41 × 10^-11 M (3σ/m). The method had high sensitivity, good stability, and good applicability to actual pork samples.

Pyridinic-Type N-Doped Graphene on Cobalt Substrate as Efficient Electrocatalyst for Oxygen Reduction Reaction in Acidic Solution in Fuel Cell

In this study, we use density functional theory to investigate the catalytic activity of graphene (G), single vacancy defective graphene (G_SV), quaternary N-doped graphene (NG_Q), and pyridinic N-doped graphene (NG_py, 3NG_py, and 4NG_py) on Co(0001) substrate for an oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). The results show pyridinic N-doped graphene on a Co support exhibited better performance than the NG_Q on a Co support and free-standing systems. According to the results, ORR intermediates (*OOH, *O, and *OH) become more stable due to the presence of a Co substrate. The single pyridinic (3NG_py) layer placed on Co(0001) is the most active site. The overpotential for Co/3NG_py is rather higher compared to pure Pt(111) catalyst (0.65 V). Therefore, pyridinic N-doped graphene with a cobalt support could be a promising strategy to enhance the ORR activity of N-doped graphene in PEMFCs.