Observation and tuning the number of weakly bonded hydrogen termination at carbon edge sites by introducing oxygen containing functional groups and optimizing heat treatment temperature

• By comparing the H 2 , D 2 and DH desorption among the samples treated at same temperatures under Ar, H 2 or D 2 , the hydrogen termination at carbon edge sites introduced by heat treatment in H 2 are quantified. • Only NB-T923-D2 shows the D 2 and DH desorption between 970 and 1800 K. • The H 2 desorption of NB-H2 are observed at lower temperature (from 970 K) than that the temperatures NB-Ar shows (from 1100 K). These results indicate that hydrogen termination formed via H 2 chemisorption is weakly bonded at edge sites. • The H 2 desorption from NB-T923-D2 are dramatically decreased while the D 2 and DH desorption from the sample are detected, which reveal the edge hydrogen on NB are isotopic exchanged by deuterium during the preHT in D 2 at 923 K. • We proved that 923 K is the optimized preHT temperature to maximize the number of weakly bonded hydrogen termination. Not only the oxygen containing functional groups but also the hydrogen termination at the edge site of carbons play a relevant role in the nature of carbon materials. Oxidized activated carbons are heat treated at various temperatures between 400 K and 1273 K under either Ar, H 2 or D 2 atmosphere. The heat treatment in H 2 simultaneously allows CO-yielding functional groups to decompose progressively and hydrogen to be chemisorbed with the formation of hydrogen termination. Temperature programmed desorption on the preheat treated samples is then performed in Ar. By comparing the H 2 , DH and D 2 desorption profiles from the samples, it is found that the chemisorbed H 2 is desorbed lower temperatures than that the edge hydrogen desorbs. Thus, it is proved hydrogen termination formed via the H 2 chemisorption is weakly bonded at edge sites. The total number of H 2 desorbed up to 1273 K during the TPD is treated as an index to the capability for the carbons to chemisorb hydrogen. The number of created weakly bonded hydrogen termination increased with increasing the preheat temperature up to 923 K, above which temperature it significantly decreased. Finally, this study proposes the specific conditions to tune the number of weakly bonded hydrogen termination.