Enhanced electrocatalysis performance of amorphous electrolytic carbon from CO2 for oxygen reduction by surface modification in molten salt

•The potential of electrolytic carbon as catalyst for oxygen reduction was evaluated.•A molten salt method for electrolytic-carbon modification was demonstrated.•The electrolytic carbon was activated for the ORR by the molten salt sulfidation.•Sulfur and cobalt dual modification further improved the ORR activity of the carbon.

The electrolytic carbon (E-carbon) derived from greenhouse gas CO2 in molten carbonates at mild temperature possesses high electrical conductivity and suitable specific surface area. In this work, its potential as catalyst is investigated towards oxygen reduction reaction (ORR). It is revealed that the pristine E-carbon has no electrocatalytic activity for the ORR due to its high surface content of carboxyl group. The carbon was then treated in a Li2SO4 containing Li2CO3-Na2CO3-K2CO3 molten salt at 550 °C. Sulfur modified E-carbon was obtained in the melt via a galvanic sulfidation reaction, in which Li2SO4 served as a nontoxic sulfur source and an oxidant. The sulfur modified E-carbon showed a significantly improved electrocatalytic activity. Subsequently, a sulfur/cobalt dual modified carbon with much higher catalysis activity was successfully prepared by treating an E-carbon/CoSO4 composite in the same melt. The dual modified E-carbon showed excellent catalytic performance with activity close to the commercial Pt/C catalyst but a high tolerance towards methanol.

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