Boosting Electrocatalytic Performance of Co(OH)2/NC for Oxygen Reduction Reaction by a Secondary-N-Doping Strategy

Improving the electrocatalysts' performance for oxygen reduction reaction (ORR) is crucial. In this work, a secondary-N-doping strategy is developed for enhancing the ORR electrocatalytic performance of Co(OH)(2)/NC, where NC is prepared from pyrolysis of carbon with melamine at 900 degrees C, then Co(OH)(2)/NC is obtained from depositing Co(OH)(2) nanosheets on NC. The secondary-N-doping strategy is carried out by pyrolyzing Co(OH)(2)/NC with melamine at 600 degrees C to form the sample named as Co/NC-N. Based on the beneficial microstructure of the increased defect degree, N content and abundant N-containing active moieties, such as pyridinic N, Co-N-x and pyrrolic-N, the obtained Co/NC-N exhibits an improved ORR peak potential (E-p) of 0.865 V and half-wave potential (E-1/2) of 0.820 V, higher than those of Co(OH)(2)/NC (0.825 V and 0.805 V), NC (0.770 V and 0.705 V), NC-N (0.779 V and 0.731 V) as well as Co/NC-N-N (0.818 V and 0.781 V). Its enhanced ORR kinetics with a Tafel value of 68 mV dec(-1) is also observed, which is lower than those of 72 mV dec(-1) for Co(OH)(2)/NC, 81 mV dec(-1) for Co/NC-N-N, 91 mV dec(-1) for NC-N and 107 mV dec(-1) for NC. This work provides a general strategy for enhancing electrocatalysts' ORR performance.