The oxygen reduction reaction （ORR） is traditionally performed using noble‐metals catalysts, e.g. Pt. However, these metal‐based catalysts have the drawbacks of high costs, low selectivity, poor stabili‐ties, and...The oxygen reduction reaction （ORR） is traditionally performed using noble‐metals catalysts, e.g. Pt. However, these metal‐based catalysts have the drawbacks of high costs, low selectivity, poor stabili‐ties, and detrimental environmental effects. Here, we describe metal‐free nitrogen‐doped carbon nanoblocks （NCNBs） with high nitrogen contents （4.11%）, which have good electrocatalytic proper‐ties for ORRs. This material was fabricated using a scalable, one‐step process involving the pyrolysis of tris（hydroxymethyl）aminomethane （Tris） at 800℃. Rotating ring disk electrode measurements show that the NCNBs give a high electrocatalytic performance and have good stability in ORRs. The onset potential of the catalyst for the ORR is-0.05 V （vs Ag/AgCl）, the ORR reduction peak potential is-0.20 V （vs Ag/AgCl）, and the electron transfer number is 3.4. The NCNBs showed pronounced electrocatalytic activity, improved long‐term stability, and better tolerance of the methanol crosso‐ver effect compared with a commercial 20 wt%Pt/C catalyst. The composition and structure of, and nitrogen species in, the NCNBs were investigated using Fourier‐transform infrared spectroscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. The pyroly‐sis of Tris at high temperature increases the number of active nitrogen sites, especially pyridinic nitrogen, which creates a net positive charge on adjacent carbon atoms, and the high positive charge promotes oxygen adsorption and reduction. The results show that NCNBs prepared by pyrolysis of Tris as nitrogen and carbon sources are a promising ORR catalyst for fuel cells.展开更多
This paper describes the procedures for the facile synthesis of 9,9′-bis(methoxymethyl)fluorene using fluorene as starting material. By hydroxymethylation and etherification reaction, the fluorene can be converted to...This paper describes the procedures for the facile synthesis of 9,9′-bis(methoxymethyl)fluorene using fluorene as starting material. By hydroxymethylation and etherification reaction, the fluorene can be converted to desired products with high yield and purity. The optimum conditions of the synthetic procedures were determined. For hydroxymethylation, the reaction temperature was 13 ℃and the mole ratio of sodium methoxide to paraformaldehyde was 0.26; and for etherification, the reaction temperature was 40 ℃and the reaction time was 15 h. Under the optimum conditions, an overall yield of 580 0 and purity of 99.20 0 were obtained.展开更多
基金supported by the National Natural Science Foundation of China (21375088,21575090)Scientific Research Project of Beijing Educational Committee (KM201410028006)+1 种基金Scientific Research Base Development Program of the Beijing Municipal Commission of EducationYouth Talent Project of the Beijing Municipal Commission of Education (CIT & TCD201504072)~~
文摘The oxygen reduction reaction （ORR） is traditionally performed using noble‐metals catalysts, e.g. Pt. However, these metal‐based catalysts have the drawbacks of high costs, low selectivity, poor stabili‐ties, and detrimental environmental effects. Here, we describe metal‐free nitrogen‐doped carbon nanoblocks （NCNBs） with high nitrogen contents （4.11%）, which have good electrocatalytic proper‐ties for ORRs. This material was fabricated using a scalable, one‐step process involving the pyrolysis of tris（hydroxymethyl）aminomethane （Tris） at 800℃. Rotating ring disk electrode measurements show that the NCNBs give a high electrocatalytic performance and have good stability in ORRs. The onset potential of the catalyst for the ORR is-0.05 V （vs Ag/AgCl）, the ORR reduction peak potential is-0.20 V （vs Ag/AgCl）, and the electron transfer number is 3.4. The NCNBs showed pronounced electrocatalytic activity, improved long‐term stability, and better tolerance of the methanol crosso‐ver effect compared with a commercial 20 wt%Pt/C catalyst. The composition and structure of, and nitrogen species in, the NCNBs were investigated using Fourier‐transform infrared spectroscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. The pyroly‐sis of Tris at high temperature increases the number of active nitrogen sites, especially pyridinic nitrogen, which creates a net positive charge on adjacent carbon atoms, and the high positive charge promotes oxygen adsorption and reduction. The results show that NCNBs prepared by pyrolysis of Tris as nitrogen and carbon sources are a promising ORR catalyst for fuel cells.
文摘This paper describes the procedures for the facile synthesis of 9,9′-bis(methoxymethyl)fluorene using fluorene as starting material. By hydroxymethylation and etherification reaction, the fluorene can be converted to desired products with high yield and purity. The optimum conditions of the synthetic procedures were determined. For hydroxymethylation, the reaction temperature was 13 ℃and the mole ratio of sodium methoxide to paraformaldehyde was 0.26; and for etherification, the reaction temperature was 40 ℃and the reaction time was 15 h. Under the optimum conditions, an overall yield of 580 0 and purity of 99.20 0 were obtained.
