Cover Picture: A Facile Strategy for Selective Incorporation of Phosphoserine into Histones (Angew. Chem. Int. Ed. 22/2013)

Nitrogen-doped Co/Co9S8/partly-graphitized carbon as durable catalysts for oxygen reduction in microbial fuel cells

“…Both pyridinic N and pyrrolic N (or graphitic N) can easily coordinate with Co to form the CoeN species, which is important for enhancing the catalytic activity for ORR [34]. However, the CoeN bonds occupy only a very small portion (6.92e14.21 at.%) of the total surface N species, and the majority of the species should be the HeN type and graphitic N. In particular, it is reported that the combination of pyridinic N and graphitic N can enhance the ORR activity through a "direct" 4e pathway as well as a "series" peroxide (2e) pathway [41]. Therefore, the high activity for ORR should be partly attributed to the co-existence of pyridinic N, graphitic N and CoeN species in the (Co)/Co 9 S 8 /NPGC-x (x ¼ 600e1000) [42].…”

“…However, it should be noted that both N and S doping play an important role in improving the ORR activity. The active sites of CoeN x and CoeS x species are probably derived from the decomposition of Co-pyridine and CoeS complexes in the raw material [41]. The current density of Co/ Co 9 S 8 /NPGC-900 (À4.71 mA cm À2 ) is slightly lower than that of Co/ Co 9 S 8 /NPGC-800 (À5.05 mA cm À2 ), and both of them are slightly lower than that of Pt/C (À5.06 mA cm À2 ).…”

“…S7, SI), which are attributed to the smooth transportation of the OH e (the 4e reaction pathway, O 2 þ 2H 2 O þ 2e e / 4OH e , not dominant) from the active sites to the anodic electrolyte and the proton from the anode to the active sites through the hierarchically porous structure of Co/Co 9 S 8 /NPGC [47]. The highest catalytic property is obtained by Co/Co 9 S 8 /NPGC-800, except the role of the Co/Co 9 S 8 heterojunction, which is mainly attributed to the synergistic effects between oxygen-containing functional groups (O-groups) and N species (cooperation of pyridinic N and graphitic N) that act as effective active-constituents for ORR via a "direct" 4e pathway (dominant) and a peroxide (2e) pathway [41]. Therefore, the accumulation of the hydrogen peroxide (H 2 O 2 ) and the formation of hydroxyl radical derived from H 2 O 2 is possible to be happened in the electrolyte, which is favorable to the inhibition of the bacterial overgrowth on the cathode [30].…”