No abstract

The most fatal disadvantage of Nafion-based proton-exchange membrane fuel cells (PEMFCs) is their significant performance losses at low relative humidities (RH ≤ 80%), making external humidification necessary. In this work, a graphene oxide (GO)-intercalated microbial montmorillonite (mMMT) layered stack (GO@mMMT) was prepared to enhance the proton conductivity of a Nafion membrane under a low humidity at elevated temperatures. The prepared mMMT had a high specific surface area and pore volume due to microbial mineralization, allowing GO to act as a spacer intercalated between MMT layers. This layered stack greatly enhanced the water absorbance and retention capacity of GO@mMMT/Nafion composite membranes. The GO@mMMT/Nafion composite membrane exhibited excellent proton conductivity under various humidities. Particularly, the 0.5GO@mMMT/Nafion sample achieved a proton conductivity of 36.4 mS·cm–1 at 80 °C/98% RH and 17.3 mS·cm–1 at 80 °C/20% RH, which was 82% and 188% higher than that of the recast Nafion membrane, respectively. The assembled single cell reached a peak power density of 546 mW·cm–2, which was 60% higher than that of the recast Nafion single cell. These results indicate that the Nafion composite membranes with GO@mMMT incorporated layered stacks show substantial potential for PEMFC applications with simplified water management.

Elastomer conductive composites (ECCs) are wonderful candidates for stretchable strain sensors. However, the sensitivity of ECC-based flexible strain sensors is limited in low-strain range, the main working range for human movements, due to the insignificant geometric change of the sample shape and weak tunneling effect of the conductive network. Herein, bioinspired heterogeneous thermoplastic polyurethane (TPU)/carbon black (CB) composites (TCs) are assembled by hot pressing two TCs with different Young’s moduli in series. The modulus of the TCs is controlled by the CB content, Young’s modulus of TPU, and plasticizer content. Experimental results and finite element analysis (FEA) confirm that the low Young’s modulus component undergoes higher strain compared with the high Young’s modulus component, resulting in a more serious change of the conductive network and higher gauge factor (GF) values. Compared with homogeneous TCs, the GF of heterogeneous TCs was improved by a factor of 20.7 and 9.6 in the low-strain (0–6%) and high-strain range, respectively. The relationship between modulus variety and GF is quantitatively described, and the GF values depend on the Young’s modulus of the individual components. Constructing a heterogeneous structure with different Young’s moduli is a valuable and facile way to increase the sensitivity of ECC-based flexible strain sensors.

No abstract