Direct methanol fuel cells system–A review of dual-role electrocatalysts for oxygen reduction and methanol oxidation

One fundamental challenge in exploiting direct methanol fuel cells (DMFCs) is the preparation of inexpensive, high active electrocatalysts, which are highly active and durable for the two half-reactions, i.e., the methanol oxidation reaction (MOR) at the anode and the oxygen reduction reaction (ORR) at the cathode. Platinum group metals-based catalysts have been known the governing dual-functional electrocatalysts based on the literature reports. But these catalysts are expensive and commercialize the DMFC less attractive. In addition to the high-cost, there are also methanol crossover, CO poisoning, long-term instability, and other problems as for Pt-based spurs. For the dual-role MOR & ORR catalysts, methanol crossover is inevitable to a certain extent on the current development of DMFC with losses in terms of cell voltage. In this regard, one strategy is to exploit high selective anodic/cathodic electrocatalysts to capitalize the energy density at a high concentration of methanol. According to the summary results, there are mainly two types of dual-role electrocatalysts: one is Pt-support/co-catalyst (designated as P-S/C) for MOR/ORR, the other is catalyst/co-catalyst (designated as C/C) for MOR/ORR. This paper aims to review the design and construction of the various dual-role catalysts and give some discussion briefly.