High-performance of polyaromatic alkaline membrane fuel cells was achieved with a polyfluorene ionomer with minimizing adsorption on hydrogen oxidation catalysts.

No abstract

Material interactions at the polymer electrolytes–catalyst interface play a significant role in the catalytic efficiency of alkaline anion-exchange membrane fuel cells (AEMFCs). In this work, the surface adsorption behaviors of the cation–hydroxide–water and phenyl groups of polymer electrolytes on Pd- and Pt-based catalysts are investigated using two Pd-based hydrogen oxidation catalystsPd/C and Pd/C-CeO2and two Pt-based catalystsPt/C and Pt-Ru/C. The rotating disk electrode study and complementary density functional theory calculations indicate that relatively low coadsorption of cation–hydroxide–water of the Pd-based catalysts enhances the hydrogen oxidation activity, yet substantial hydrogenation of the surface adsorbed phenyl groups reduces the hydrogen oxidation activity. The adsorption-driven interfacial behaviors of the Pd- and Pt-based catalysts correlate well with the AEMFC performance and short-term stability. This study gives insight into the potential use of non-Pt hydrogen oxidation reaction catalysts that have different surface adsorption characteristics in advanced AEMFCs.

For the first time, we report that graphene oxide (GO) can be used as a new "dual-role" binder for Si nanoparticles (SiNPs)-based lithium-ion batteries (LIBs). GO not only provides a graphene-like porous 3D framework for accommodating the volume changes of SiNPs during charging/discharging cycles, but also acts as a polymer-like binder that forms strong chemical bonds with SiNPs through its Si-OH functional groups to trap and stabilize SiNPs inside the electrode. Leveraging this unique dual-role of GO binder, we fabricated GO/SiNPs electrodes with remarkably improved performances as compared to using the conventional polyvinylidene fluoride (PVDF) binder. Specifically, the GO/SiNPs electrode showed a specific capacity of 2400 mA h g at the 50th cycle and 2000 mA h g at the 100th cycle, whereas the SiNPs/PVDF electrode only showed 456 mAh g at the 50th cycle and 100 mAh g at 100th cycle. Moreover, the GO/SiNPs film maintained its structural integrity and formed a stable solid-electrolyte interphase (SEI) film after 100 cycles. These results, combined with the well-established facile synthesis of GO, indicate that GO can be an excellent binder for developing high performance Si-based LIBs.

This research introduces the design of a gas-diffusional cathode employing bilirubin oxidase (BOx) immobilized on a complex matrix composed of carbon nanotube (CNT) modified Toray paper (TP) and, encapsulated in silica-gel. The developed enzymatic cathode consists of two layers. One is the hydrophobic gas-diffusional layer (GDL) and the other a hydrophilic catalytic layer (CL) which were combined by pressing at 1000 psi for five minutes. The GDL (35% weight teflonized Vulcan carbon powder (XC35)) that is exposed to air has hydrophobic and porous properties that facilitate oxygen diffusion. The CL consists of a thin, high surface area, 3D CNT/silica-gel matrix where the 3D-enzymatic structure is immobilized and preserved. The nanostructured architecture of the CL was designed to improve conductivity and surface area. Such a design was achieved by modifying the TP surface with CNTs. CNTs are grown on TP by chemical vapor deposition which is possible by electrodepositing Ni seeds via pulse chronoamperometry. Entrapment of BOx was achieved by using tetramethyl orthosilicate (TMOS), a highly volatile compound that results in a polymeric condensation reaction with H 2 O at room temperature. TMOS polymerization of the cathode surface was performed in a chemical vapor deposition process to form a silica-gel matrix. The gas diffusional cathode was assembled to a capillary driven microfluidic system to be electrochemically characterized. The characterization was performed from electrolyte pH 5 to pH 8 with increments 0.5 in pH. The best performance was observed at pH 5.5 showing a current output of 655.07 ± 146.18 μA.cm −2 and 345.36 ± 30.04 μA.cm −2 at 0 V and 0.3 V, respectively. At a pH of 7.5 the current generated was 287.05 ± 20.37 μA.cm −2 and 205.37 ± 1.57 μA.cm −2 at 0 V and 0.3 V, respectively. The results show the stability of the enzymatic structure, subject to various pH, is maintained within the 3D-CNT silica-gel matrix for pH lower than 8. Future work will focus on storage life and stability over time. Interest in biofuel cells has increased in the past decade in pursue of self energetically-sustained biomedical devices and also small, portable electrical devices capable of work by harvesting energy from natural fuel sources. Such interests exist due to the low temperature and neutral pH operating range of biofuel cells.1-3 Depending on the mechanism of the enzyme, either direct or mediated electron transfer (DET and MET, respectively) reflects the electron transfer distance between enzyme active site and electrode interface. One must couple mediators/cofactors for the latter in order to have electrons transferred to the electrode and further to an external circuit therefore subjecting electrons to a diffusion distance.2,4-13 On the other hand DET works under an electron tunneling distance. Further design considerations are centered on the three main regions of inherent energetic losses in fuel cells known as kinetic, ohmic and mass transfer limits. Although there are many different ways to design an enzymat...