This article provides calibration spectra for determining the transmission function of an XPS instrument operating with an Ag Lα (2984.3 eV) source monochromated with a quartz (1010) crystal through second order diffraction and irradiating the sample at 54.7° to the surface normal.

Bipolar plates are one of the main components of proton exchange membrane fuel cells (PEMFCs). Their functions include distributing reactants, supporting the cell, and conducting heat and electricity. They account for a significant proportion of the fuel cell stack’s weight and volume. The main materials currently used for bipolar plates are graphite and stainless steel. Aluminium has a much lower density than steel and is easier to form than both steel and graphite. Its use, therefore, would allow fuel cells with higher power densities but is hindered due to it being prone to corrosion. This work focused on the development of corrosion-resistant and conductive coatings to address this issue. Carbon coatings with Ti and Cr adhesion layers were deposited on aluminium substrates using closed-field unbalanced magnetron sputtering. These coatings were tested for corrosion properties and performance on the cathode side of a single-cell fuel cell. Coated aluminium samples were also tested for their ability to maintain their corrosion protection after being formed. Coating with a Cr adhesion layer outperformed that with a Ti adhesion layer in both forming and fuel cell tests, demonstrating much lower performance degradation after accelerated stress testing.

Aluminium is an attractive material for proton-exchange-membrane fuel cell bipolar plates as it has a much lower density than steel and is easier to form than both steel and graphite. This work focused on the development of amorphous carbon films deposited using closed-field unbalanced magnetron sputtering (CFUBMS) in order to improve the corrosion resistance of aluminium bipolar plates and to enhance fuel cell performance and durability. Chromium and tungsten adhesion layers were used for the coatings. It was possible to achieve good electrical conductivity and high electrochemical corrosion resistance up to 70 °C on polished Aluminium alloy 6082 by tuning the deposition parameters. Coatings with a tungsten adhesion layer showed better corrosion resistance than those with a chromium adhesion layer. In situ, accelerated stress testing of single cells was performed using uncoated and coated Al6082 bipolar plates. Both coatings resulted in improved fuel cell performance compared to uncoated aluminium when used on the cathode side of the fuel cell.

The scarcity of iridium-based water oxidation electrocatalysts limits the scaling up of proton exchange membrane (PEM) water electrolysers. Developing conductive and stable supports is an effective way to reduce iridium loading. However, it is very challenging to find materials that are both stable and conductive under the corrosive and oxidative oxygen evolution reaction (OER) conditions. Nb-doped TiO2 is a potential candidate with Nb dopant improving the conductivity of TiO2. However, its conductivity is still around 10 orders of magnitude lower than IrO2. Herein, we have fabricated a series of Ti-Nb alloy thin films with varied Nb content by sputter deposition and investigated their performance as a support for iridium oxide. Electrochemistry and accelerated stress test were conducted on these metal thin films and characterisation techniques including X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy were employed to characterise the in situ formed passivation layers during the OER. Our results suggested that a ~10 nm oxide passivation layer forms on Ti-based supports. On alloying Nb with Ti metal, a more insulating rutile Ti oxide phase forms under OER whereas an anatase Ti oxide, with higher conductivity, is observed on the undoped Ti. Consequently, although alloying with Nb improves the bulk conductivity, the structure of the oxide passive layer results in drastic decrease of conductivity, and OER activity for Nb-containing supports. Our results thus indicate the importance of the structure and composition of surface oxide phases formed during OER in controlling the overall stability and conductivity of candidate support materials.