A High‐Performance Direct Methanol Fuel Cell Technology Enabled by Mediating High‐Concentration Methanol through a Graphene Aerogel

Abstract

conventional DMFCs was significantly underdeveloped due to the mandatory usage of diluted methanol solutions as media, yielding a limit methanol transportation efficiency and the detrimental consequences. [2,3] Graphene aerogels (GAs), a group of carbon metamaterials, have attracted considerable interests for its potential applications, such as supercapacitors, [4] electrodes, [5,6] catalysis, [7,8] sensors, [9] and environmental remediation. [5,10,11] Their unique properties-high porosity, high surface area, ultralight weight (<10 mg cm −3 ), [12,13] excellent elasticity (>90% in compression), [14,15] and high electrical conductivity (≈10 S cm −1 ) [8,16,17] -have enabled wide applications such as electrodes and current collectors in polymer electrolyte fuel cells. [17][18][19][20] By far, most of the reported fabrications of GAs are in laboratory scale, i.e., chemical vapour deposition, [21] template-mediated assembly, [22] 3D-printing-based rapid manufacturing, [14,23] and self-assembly. [12,24] A fabrication strategy with potential to be scaled-up to being integrated to current industrial process would be highly desired. Taking the advantages of high porosity and high surface area, GAs can kinetically improve the electrochemical performance by offering diffusion-based mass transport, high absorption capacities, and ultrafast absorption rate for organic solvents and oils, as being explored previously by other researchers. The interesting results reported by Sun et al showed that their GA can absorb 344 times of its own weight of toluene completely within 5 s. [13] Li et al. prepared GA with absorption capacity of 229 times ethanol and 465 times chloroform of its own weight, respectively. [24] Traditional DMFCs require multiple components to fulfil the functions, e.g., methanol cartridge as reservoir, a gasdiffusion layer (GDL), and a flow field plate (FFP) for mass and heat transfer, current collection, fuel and oxygen diffusion, and kinetic control. Compared to the remarkable progresses on materials innovations for high energy performance, optimization of DMFC design for high energy output has been less exploited; therefore, challenges remains such as ohmic losses induced by the poor electrical conductivity of GDL and FFP, and bulky and heavy weight of FFP, because it was made from A facile methodology to fabricate graphene aerogel (GA), and its application in a direct methanol fuel cell (DMFC), is demonstrated for the first time. A new GADMFC design is proposed by using GA to replace two main components within the DMFC-the gas-diffusion layer and the flow field plate. The results indicate a 24.95 mW cm −2 maximum power density of air polarization is obtained at 25 °C. The membrane electrolyte assembly has a 63.8% mass reduction compared to an ordinary one, which induced 3 times higher mass power density. Benefiting from its excellent organic solvent absorbency, the methanol crossover effect is dramatically suppressed while using 12 m methanol, therefore, a higher concentration or even pure methanol can...

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