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 °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 °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.