TY - JOUR
T1 - Deciphering the role of quaternary N in O2 reduction over controlled N-doped carbon catalysts
AU - Haque, Enamul
AU - Zavabeti, Ali
AU - Uddin, Nizam
AU - Wang, Yichao
AU - Rahim, Md. Arifur
AU - Syed, Nitu
AU - Xu, Kai
AU - Jannat, Azmira
AU - Haque, Farjana
AU - Zhang, Bao Yue
AU - Shoaib, Mahbubul Alam
AU - Shamsuddin, Sayed
AU - Nurunnabi, Md.
AU - Minett, Andrew I.
AU - Ou, Jian Zhen
AU - Harris, Andrew T.
PY - 2020
Y1 - 2020
N2 - Nitrogen-doped carbon catalysts prepared from amino-functionalized metal-organic frameworks [amino-MIL-101(Al)] were investigated for the oxygen-reduction reaction (ORR) with special emphasis on elucidating the role of different nitrogen species (e.g., pyridinic, pyrrolic, and quaternary N) as active catalytic sites. Careful optimization of pyrolysis temperature of the amino-MIL-101(Al) leveraged the synthesis of the catalysts with or without quaternary N functionalities. This allowed us to investigate the type(s) of N species responsible for the ORR catalysis and thus address the conflicting results reported so far regarding the pyridinic and/or quaternary N as active sites for ORR catalysis via four-electron transfer (4e-) pathways. Our findings suggest that the total nitrogen content in the catalysts does not influence the ORR, while the quaternary N sites exclusively catalyze the reduction of O2 via the 4e- transfer pathway in both alkaline and acidic electrolytes. Catalysts containing only pyridinic and pyrrolic N were observed to be ineffective for the ORR. The experimental results were further supported by computational simulation using the gradient-correlated density functional theory which revealed that the dissociative O2 adsorption (i.e., binding and cleavage of O═O bonds) is more favorable to quaternary N. Furthermore, calculations based on the relative surface potential energy, dipole moment, binding energy, and electron density indicate that the most stable structure of O2 chemisorption sites could only be achieved on the quaternary N carbon.
AB - Nitrogen-doped carbon catalysts prepared from amino-functionalized metal-organic frameworks [amino-MIL-101(Al)] were investigated for the oxygen-reduction reaction (ORR) with special emphasis on elucidating the role of different nitrogen species (e.g., pyridinic, pyrrolic, and quaternary N) as active catalytic sites. Careful optimization of pyrolysis temperature of the amino-MIL-101(Al) leveraged the synthesis of the catalysts with or without quaternary N functionalities. This allowed us to investigate the type(s) of N species responsible for the ORR catalysis and thus address the conflicting results reported so far regarding the pyridinic and/or quaternary N as active sites for ORR catalysis via four-electron transfer (4e-) pathways. Our findings suggest that the total nitrogen content in the catalysts does not influence the ORR, while the quaternary N sites exclusively catalyze the reduction of O2 via the 4e- transfer pathway in both alkaline and acidic electrolytes. Catalysts containing only pyridinic and pyrrolic N were observed to be ineffective for the ORR. The experimental results were further supported by computational simulation using the gradient-correlated density functional theory which revealed that the dissociative O2 adsorption (i.e., binding and cleavage of O═O bonds) is more favorable to quaternary N. Furthermore, calculations based on the relative surface potential energy, dipole moment, binding energy, and electron density indicate that the most stable structure of O2 chemisorption sites could only be achieved on the quaternary N carbon.
UR - https://hdl.handle.net/1959.7/uws:71486
U2 - 10.1021/acs.chemmater.9b03354
DO - 10.1021/acs.chemmater.9b03354
M3 - Article
SN - 1520-5002
SN - 0897-4756
VL - 32
SP - 1384
EP - 1392
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 4
ER -