Increased SO2 electrooxidation activity on a copper-nitrogen doped catalyst and its active sites analysis

It's a meaningful work to develop a highly active nonprecious SO2 electrooxidation catalyst, replacing the Pt-based ones. Here, a novel Cu-N doped carbon-based catalyst is synthesized by pyrolyzing the imidazole chelated copper ions on the chitosan modified carbon BP2000. During the preparation, metallic Cu is developed and encapsulated in the carbon lattices, and transformed into the CuNx structures on the catalyst surface, simultaneously. Metallic Cu plays significant role in the doping and developing of active sites, which have vital effects on the catalysis activity. The prereduction of Cu2+ by NaBH4 during the preparation of Doping(I)-Cu@N-C makes great contribution to the development of metallic Cu, which highly dispersive anchor in the carbon lattices. This as-synthesized Doping(I) -Cu@N-C catalyst exhibits excellent SO2 electrooxidation activity. Its SO2 oxidation currents are remarkably increased with the elevation of applied potentials, and the oxidation performances prominently surpass the commercial Pt/C, when the potential is above 0.822 V. The peak SO2 oxidation current (ip) of Doping(I)-Cu@N-C is 7.17 mA cm−2 @ 0.684 V, much higher than the 3.03 mA cm−2@ 0.584 V of Pt/C with the same mass loading. In the chronoamperometry tests under 1.2 V, the terminal oxidation current of Doping(I)-Cu@N-C was 1.74 times as high as that of Pt/C, indicating that this prepared catalyst also displays much better SO2 electrooxidation activity than Pt/C under constant applied potentials.