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2D atomic crystals such as single layer graphene (SLG) and hexagonal boron nitride (hBN) have been shown to be 'unexpectedly permeable' to hydrogen ions under ambient conditions with the proton conductivity rising exponentially with temperature. Here, the first successful addition of SLG made by a chemical vapor deposition (CVD) method is shown to an operational direct methanol fuel cell significantly enhancing the performance of the cell once the temperature is raised above 60 °C, the temperature at which the proton conductivity of SLG is higher than the Nafion membrane on which it is mounted. Above this temperature, the resistance to proton transport of the system is not affected by the graphene but the barrier properties of graphene inhibit methanol crossover. The performance of the fuel cell is shown to increase linearly with coverage of SLG above this temperature. Results show that the maximum power density is increased at 70 °C by 45% in comparison to the standard membrane electrode assembly without graphene. In addition, a membrane with CVD hBN shows enhanced performance across the entire temperature range due to better proton conductivity at lower temperatures. [ABSTRACT FROM AUTHOR]

Stabilisation of metal species using hydroxyl‐rich dealuminated zeolites is a promising method for catalysis. However, insights into the interactions between the hydroxyl groups in zeolite and noble metals and their effects on catalysis are not yet fully understood. Herein, comparative studies were conducted using Pt catalysts supported on hydroxyl‐rich dealuminated Beta (deAl‐Beta) and the pristine proton‐form Beta (H‐Beta) for catalytic oxidation of toluene. The findings suggest that during impregnation the Pt precursor (i. e., Pt(NH3)4(NO3)2) interacted with different sites on deAl‐Beta and H‐Beta, leading to the formation of supported Pt nanoparticles with different physicochemical properties. In detail, for H‐Beta, the Pt precursor interacted with Al‐OH and isolated external Si‐OH sites, yielding Pt NPs with a higher Pt0 proportion of ~71 % compared to ~57 % Pt0 on deAl‐Beta. Comparatively, abundant hydroxyl groups on deAl‐Beta such as silanol nest and isolated internal Si‐OH stabilised highly active Pt‐O species. The resulting Pt/deAl‐Beta exhibited improved activity and anti‐coking ability than Pt/H‐Beta in catalytic toluene oxidation. For example, the temperature for 50 % toluene conversion was 193 °C for Pt/deAl‐Beta vs. 232 °C for Pt/H‐Beta, and the coke deposition was 1.7 % vs. 6.7 % (after the 24‐h longevity test), respectively. According to the toluene‐temperature programmed desorption (toluene‐TPD), 1H nuclear magnetic resonance (1H NMR) relaxation and in situ diffuse reflection Fourier transform spectroscopy (in situ DRIFTS) characterisation, the enhanced performance of Pt/deAl‐Beta could be ascribed to (i) the active Pt‐O sites stabilised by hydroxyl groups, which interact with toluene easily for conversion, and (ii) the acid‐free feature of the deAl‐Beta support, which avoids the formation of coke precursors (such as benzoate species) on the catalyst surface. Findings of the work can serve as the design guidelines for making effective supported metal catalysts using zeolitic carriers. [ABSTRACT FROM AUTHOR]

Nigerian kaolin is converted into pure zeolite-A by calcination of the kaolin at 650 °C for ten minutes, followed by mixing the obtained metakaolin with a zeolite seed, NaOH, and H2O (autoclave, 100 °C, 3 h). [ABSTRACT FROM AUTHOR]