Investigation of Non-Precious Metal CoN4-Based Oxygen Reduction Catalyst by Electrochemical and X-ray Absorption Spectroscopy Techniques

Abstract

Electrochemical and X-ray absorption techniques are applied to determine the influence of pyrolysis and nitrogen-containing precursor loading on the catalytic activity and structure of carbon-supported cobalt triethylenetetramine (CoTETA/C) catalyst. These CoTETA/C catalysts with different nitrogen-containing precursor loadings are synthesized from pyrolyzing cobalt triethylenetetramine supported on carbon at 800°C in Ar atmosphere. For comparison, the as-prepared (without pyrolysis) is also studied. Cyclic voltammograms and rotating disk electrode measurements indicate that the as-prepared presents very low activity, while the CoTETA/C catalysts with different nitrogen-containing precursor loadings show good catalytic activity and the maximum is found for CoTETA/C catalyst with Co:TETA = 1:4. X-ray absorption measurements at Co and N K edges show that after pyrolysis the CoN4 centers are no longer detected along with little nitrogen atoms inserted into carbon matrix and nanometallic α-Co clusters are formed. X-ray diffraction also confirms the presence of nanometallic α-Co particles on the catalysts.