Essential analysis of cyclic voltammetry of methanol electrooxidation using the differential electrochemical mass spectrometry

Using the cyclic voltammetry to test the performance of methanol electrooxidation is the most popular method to seek anodic catalysts for direct methanol fuel cells. A cyclic voltammetry of methanol electrooxidation typically has two peaks on Pt-based catalysts: one peak of P_f with the current of j_f in the forward scan, the other peak of P_b with the current of j_b in the backward scan. The ratio of j_f/j_b is an intensively used criterion to evaluate the ability of CO tolerance of Pt-based catalysts. In this study, however, it is demonstrated that both peak currents are ascribed to the consumption of methanol at the surface of the electrode using the differential electrochemical mass spectrometry (DEMS). In addition, our results reveal that the peak area ratio should be a criterion linking to the overlapping region between the potentials of methanol oxidation and the potentials of the reduction of the oxidized surface generated in the forward scan. Based on our analysis, the ratio of the integrated current of P_f and P_b can be a new descriptor to describe the reducibility of the oxidized Pt surface formed at high potential instead of CO anti-poisoning of the catalyst.