Sulfonic acid functionalized graphene (S-graphene) is explored as a potential inorganic filler as well as a solid acid proton conducting medium to realize a hybrid membrane with Nafion for a direct methanol fuel cell (DMFC). The simple, but effective, functionalization of graphene is performed by sulfonic acid containing aryl radicals to increase the number of sulfonate groups per unit volume of graphene domain. Nafion−S-graphene hybrid membranes increase compactness of ionic domains and enhanced proton conductivity while restricting the methanol crossover across the membrane. DMFCs with a Nafion−S-graphene (1 wt %) hybrid membrane deliver a peak power density of 118 mW cm −2 at a load current density of 450 mA cm −2 while operating at 70 °C under an ambient pressure. By contrast, operating under identical conditions, a peak power density of 54 mW cm −2 at a load current density of 241 mA cm −2 is obtained with the pristine recast Nafion membrane. The Nafion−S-graphene hybrid membranes are extremely beneficial and useful for DMFCs in addressing many critical problems associated with commercial Nafion membranes.

Herein, a new type of cobalt encapsulated nitrogen-doped carbon (Co@NC) nanostructure employing Zn Co (C H N ) metal-organic framework (MOF) as precursor is developed, by a simple, ecofriendly, solvent-free approach that utilizes a mechanochemical coordination self-assembly strategy. Possible evolution of Zn Co (C H N ) MOF structures and their conversion to Co@NC nanostructures is established from an X-ray diffraction technique and transmission electron microscopy analysis, which reveal that MOF-derived Co@NC core-shell nanostructures are well ordered and highly crystalline in nature. Co@NC-MOF core-shell nanostructures show excellent catalytic activity for the oxygen reduction reaction (ORR), with onset potential of 0.97 V and half-wave potential of 0.88 V versus relative hydrogen electrode in alkaline electrolyte, and excellent durability with zero degradation after 5000 potential cycles; whereas under similar experimental conditions, the commonly utilized Pt/C electrocatalyst degrades. The Co@NC-MOF electrocatalyst also shows excellent tolerance to methanol, unlike the Pt/C electrocatalyst. X-ray photoelectron spectroscopy (XPS) analysis shows the presence of ORR active pyridinic-N and graphitic-N species, along with CoN C and CoN ORR active (M-N-C) sites. Enhanced electron transfer kinetics from nitrogen-doped carbon shell to core Co nanoparticles, the existence of M-N-C active sites, and protective NC shells are responsible for high ORR activity and durability of the Co@NC-MOF electrocatalyst.

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We summarize here recent advancements in Pt rare earth metal alloy and metal oxide catalysts for oxygen reduction and alcohol oxidation reactions.

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A noble metal-free electrocatalyst for an efficient oxygen reduction reaction under both alkaline and acidic conditions has been fabricated by a one-pot template-free strategy.