The strong growing interest in using direct methanol fuel cells (DMFCs) as portable and mobile power sources is rooted in their desirable features of relatively small environmental footprint, compact system design, and higher volumetric energy densities compared with existing technologies.  

Currently, the anode and cathode catalysts of DMFCs are commonly based on platinum (Pt). These catalysts are not selective to methanol oxidation reaction (MOR) at anode or oxygen reduction reaction (ORR) at cathode, and hence any methanol crossover from the anode to the cathode through the PEM can be oxidized by the cathode catalyst. This results in the creation of a mixed potential at the cathode, which significantly degrades the fuel cell performance.  

In general, dilute methanol solutions (< 4 M) are often used as fuel for DMFCs in order to inhibit the methanol crossover. However, to compete with lithium-based rechargeable batteries that currently dominate the portable power market, the use of high-concentration methanol (9 M or higher) as fuel is highly demanded to capitalize the high energy density of DMFCs. 

Commonly, scientists use various strategies to improve DMFC performance at high concentrations of methanol. These include improving the fuel-feed system, membrane development, modification of electrodes, and water management. Unfortunately, these approaches would not fundamentally overcome this key obstacle, but inevitably complicate the design of the DMFCs and hence increase their cost. 

Instead, a research group led by Prof. YANG Jun at Institute of Process Engineering (IPE), Chinese Academy of Sciences (CAS) demonstrates the use of selective electrocatalysts to run a DMFC at methanol concentration up to 15 M.  

Upon the deep understanding of the mechanisms of the electrode reactions in DMFCs, they designed and produced noble metal-based heterogeneous nanomaterials with enhanced catalytic activity and high selectivity towards DMFC reactions by sufficiently making use of the structural uniqueness and electronic coupling effects among the different domains of the electrocatalysts so that the DMFCs can be operated well with high-concentration methanol as fuel. 

As shown in Fig. 1, ternary Au-Ag2S-Pt nanocomposites with core-shell-shell structures display superior anode selectivity due to the electronic coupling among their different domains, while core-shell Au-Pd nanoparticles with thin Pd shells exhibit excellent cathode selectivity because of the synergistic effects between their Au core and thin Pd shell.