Synthesis and evaluation of HfO₂ as a prospective filler in inorganic–organic hybrid membranes based on Nafion for PEM fuel cells

Abstract

Hybrid inorganic-organic Nafion membranes modified with metal oxides (typically TiO 2 , ZrO 2 , WO 3 ) are a good alternative for fuel cell applications. However, one of their main limitations is associated with their relative low proton conductivity at temperatures above 80 °C. In this work, we overcome this issue using HfO 2 as a filler. HfO 2 was prepared by a sol-gel method, and it was compared with a recast Nafion membrane (named as recast). Deconvolved XPS spectra confirmed the presence of hafnia, while EDS analysis was used to determine its weight content resulting in a 1.88 wt%. FT-IR ATR experiments indicated that the HfO 2 hybrid membrane possess a higher capability to retain water than the recast. Thus, the water uptake, swelling degree, conductivity tests and fuel cell evaluations were performed. The water uptake analysis revealed that the hybrid membrane presented a higher retention percentage at 100 °C (61%) than recast (29%). This improvement enabled a higher ionic conductivity at 80 °C and 100 °C. The hybrid membrane displayed a higher conductivity at 100 °C than the recast membrane (112 versus 82 mS cm −1 ), increasing the cell performance to 0.36 W cm −2 ; being this performance almost two-fold higher to that obtained for the recast membrane. In summary, herein we demonstrated that HfO 2 can be considered as an excellent substitute to conventional fillers.

An Intermetallic CaFe6Ge6 Approach to Unprecedented Ca−Fe−O Electrocatalyst for Efficient Alkaline Oxygen Evolution Reaction

“…In particular, the peaks of C1 (285 eV) and C4 (290.1 eV) were reported in the case of vaterite‐phase CaCO 3 , corresponding to the C−C bond, as well as CO 3 2− , respectively [41,43] . Note another two C1s peaks (C5 and C6) were non‐negligible, which both resulted from the utilization of the Nafion binder [44] …”

“…[41,43] Note another two C1s peaks (C5 and C6) were non-negligible, which both resulted from the utilization of the Nafion binder. [44] Furthermore, deeper investigation into the in-situ reconstructed porous CaÀ FeÀ O (vaterite-phase CaCO 3 coupled with α-Fe III OOH) heteroshell could also be achieved using a combination of ex-situ and in-situ Raman spectroscopy, supplemented by IR measurements. During the OER CA process, the NF substrate might also participate in the reaction through oxidation into the Fe-doped Ni-based (oxy)hydroxides, [28,45] which can interfere with the analysis of the Raman and IR spectroscopic data while monitoring the structural reconstruction of CaFe 6 Ge 6 during water oxidation.…”

Recent Advancements in the Synthesis and Application of Carbon-Based Catalysts in the ORR

“…Some research has focused on improving these Nafion membranes by developing composite membranes with inorganic components like TiO 2 and WO 2 [115]. Pineda-Delgado et al [116] investigated the incorporation of HfO 2 as a filler in composite Nafion membranes. By using a sol-gel-like process they were able to integrate a low percentage of HfO 2 (1-3 wt%) into the Nafion membrane.…”

Composite Polymers Development and Application for Polymer Electrolyte Membrane Technologies—A Review

“…Pineda-Delgado et al [147] decided to study the behaviour and performance of Hafnium oxide Nafion composite membranes. The fabricated composite membranes displayed greater water uptake of 61% at 100 • C compared to 29% for recast Nafion.…”