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Nafion, a perfluorosulfonic acid polymer, has been the standard membrane material for direct methanol fuel cells (DMFCs) due to its proton-carrying capabilities, despite its shortcomings as a methanol barrier. To attain self-healing and methanol-blocking properties, the incorporation of poly(vinyl alcohol) (PVA) polymer into Nafion was pursued. However, this strategy resulted in low proton conductivity. Thus, acid functional groups were added to a secondary modifier to boost proton conductivity. In this work, sulfonated graphene oxide (SGO) was assembled with Nafion and PVA through a simple freezing-thawing method to demonstrate a self-healable proton exchange membrane (PEM) without compromising the proton conductivity of Nafion. The synergistic effect of SGO in methanol-blocking and proton transport successfully strode over recast Nafion by hampering 33.2 % of methanol permeation and increasing 19.5 % of proton conductivity. As a result, the selectivity of the best hybrid PEM (N/PVA/SGO1.0) was increased by 1.8 times in comparison to recast Nafion. A single cell passive DMFC made using the novel hybrid membrane exhibited a power density of 6.07 mW cm−2 at a current density of 26.48 mA cm−2, and an open circuit voltage of 0.55 V at room temperature using 4 M methanol. This performance was essentially higher than that achieved by recast Nafion and commercial Nafion 117. The N/PVA/SGO1.0 hybrid membrane also showed remarkable self-healing properties, with 89 % recovery of methanol blocking function through reversible hydrogen bonding, illustrating its tremendous sustainable potential for use in DMFCs. [Display omitted] • Freeze-thaw process induces reversible physical crosslinking in N/PVA/SGO. • N/PVA/SGO achieves 28 % better DMFC performance than N117. • N/PVA/SGO demonstrates multiple times of self-healing. [ABSTRACT FROM AUTHOR]

Abstract Concentrated photovoltaic cell (CPV) had gained much attention recently due to high efficiency at a competitive cost. However, efficiency of CPV is inversely proportional to the temperature. Hence, it is important to reduce the maximum temperature and variation of temperature across the CPV. Metal foam with its high specific surface area, thermal conductivity and tortuous flow path to promote mixing is an ideal candidate for thermal management for CPV. However, the thermal performance of the metal foam may drop from upstream to downstream and lead to poor cooling performance near the outlet. In this study, functionally graded metal foam is attached on the CPV to extract the heat generated. Functionally graded aluminum foam with gradual variation porosity are modelled to investigate the thermal performance and flow field using computational thermal fluid dynamics analysis. Heat transfer correlation, permeability and resistance loss coefficient are extracted from the literature and used in the simulation. The results showed that functionally graded metal foam with gradual reducing porosity offered a better temperature uniformity for the CPV. Therefore, this approach will further extend the cycle life as well as improve the overall efficiency of the CPV. [ABSTRACT FROM AUTHOR]