Significant progress has been made in the development of non-precious metal electrocatalysts （NPMEs） during the past decade. Correspondingly, there is an urgent demand for an appropriate measurement method to be established for the reliable evaluation of NPMEs. In this study, platinum and graphite counter electrodes were used to investigate the impact of counter electrode material on the accelerated durability testing （ADT） of NPMEs in acidic medium. Platinum used as the coun- ter electrode in a traditional three-electrode electrochemical cell was found to dissolve in acidic medium and re-deposit on NPME coated on the working electrode during ADT. Such re-deposition causes the oxygen reduction reaction （ORR） performance of NPMEs to remarkably improve, and thus will seriously mislead our judgment of NPMEs if we are unaware of it. The phenomenon can be avoided using a graphite counter electrode.
The development of a non-precious metal electrocatalyst （NPME） with a performance superior to commercial Pt/C for the oxygen reduction reaction （ORR） is important for the commercialization of fuel cells. We report the synthesis of a NPME by heat-treating Co-based metal organic frameworks （ZIF-67） with a small average size of 44 nm. The electrocatalyst pyrolyzed at 600 ~C showed the best performance and the performance was enhanced when it was supported on BP 2000. The resulting electrocatalyst was composed of 10 nm Co nanoparticles coated by 3-12 layers of N doped graphite layers which as a whole was embedded in a carbon matrix. The ORR performance of the electrocatalyst was tested by rotating disk electrode tests in O2-saturated 0.1 mol/L KOH under ambient conditions. The electrocatalyst （1.0 mg/cm~] showed an onset potential of 1.017 V （[vs. RHE] and a half-wave potential of 0.857 V （vs. RHE], which showed it was as good as the commer- cial Pt/C （20 BgPt/cm2）. Furthermore, the electrocatalyst possessed much better stability and re- sistance to methanol crossover than Pt/C.
