Synthesis and catalysis of copper sulfide/carbon nanodots for oxygen reduction in direct methanol fuel cells

Abstract

We have fabricated Cu2−xS/carbon nanodot (C dot) electrodes for direct methanol fuel cells (DMFCs). To the best of our knowledge, this is the first time that Cu2−xS/C dot nanomaterials (NMs) were proposed to be used as a cathode catalyst for oxygen reduction reaction (ORR) in acidic media. The structural characterizations revealed that Cu2−xS alloy possessed two types of crystalline phases, such as Cu9S5 and Cu2S in the structure of Cu2−xS/C dot NMs. The onset potential of the ORR for Cu2−xS/C dot NMs is 0.92V (vs. Ag/AgCl), revealing a good ORR activity of these NMs. The Cu2−xS/C dot electrodes (mass loading: 2.26mgcm−2) provide a mean limiting density of −1.77mAcm−2 at a scan rate of 5mVs−1 and rotation rate of 3600rpm. Electrochemical impedance spectrometry (EIS) results revealed that the charge-transfer resistance (Rct) of the Cu2−xS/C dots was smaller than that of Cu2−xS/CNT. In addition, compared with Pt/C electrodes, Cu2−xS/C dot electrodes were more tolerant against MeOH poisoning. The low-cost, electrochemically stable, and highly active Cu2−xS/C dot electrode has great potential for use in DMFCs.