Fabrication of NbN-Coated Porous Titanium Sheets for PEM Electrolyzers
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JMEPEG https://doi.org/10.1007/s11665-020-05026-y
Fabrication of NbN-Coated Porous Titanium Sheets for PEM Electrolyzers N.F. Daudt
, A.D. Schneider, E.R. Arnemann, C.J. Scheuer, L.S. Dorneles, and L.F. Schelp (Submitted April 13, 2020; in revised form June 22, 2020)
Porous titanium sheets are attractive for application as the porous transport layer (PTL) for polymer electrolyte membrane (PEM) water electrolyzers. However, the titanium passivation increases its surface contact resistance, deteriorating the electrolyzer performance. A solution for long-term operation has been to coat titanium-based PTLs with platinum or gold, which considerably increases PEM electrolyzer costs. To overcome this limitation, a NbN coating is proposed as an alternative to decrease materials costs while avoiding titanium surface oxidation. Therefore, porous titanium sheets of ca. 250 lm were powder metallurgically produced by tape casting and then sputter-coated with a NbN thin film. A systematic investigation of NbN film deposition on porous titanium sheets by reactive magnetron sputtering was undertaken. Coating microstructure and constitution were evaluated before and after electrochemical characterization. First electrochemical characterizations throughout cyclic voltammetry and potentiodynamic polarization curves demonstrate that the addition of NbN coatings decreases titanium surface oxidation and improves electrochemical performance of the porous titanium sheets. These results indicated that NbN-coated PTLs are promising candidates for PEM electrolyzer application. Keywords
NbN coatings, porous titanium sheets, PEM water electrolyzer, porous transport layer, reactive magnetron sputtering
1. Introduction Hydrogen is expected to play a key role as energy carrier in the future (Ref 1). Among the technologies available for hydrogen production, water electrolysis shows great promise as an efficient solution to store renewable energy. Herewith, polymer electrolyte membrane (PEM) water electrolysis has attracted huge attention for sustainable production of hydrogen, due to its low operation temperature, high current density, high efficiency and high purity of the produced H2. The configuration of a PEM electrolyzer is similar to a PEM fuel cell; it consists of an anode and a cathode separated by a solid polymeric electrolyte, commonly a Nafion membrane as shown in Fig. 1. At the anode, the water is split into oxygen, protons and electrons; the protons cross the membrane and are reduced to H2 at the cathode. The anode side combines high overpotential, acid environment and presence of water and oxygen mixture. For this reason, materials with high corrosion resistance, such as iridium- and titanium-based components, have been used on the anode side. However, the high costs and
N.F. Daudt, E.R. Arnemann, and C.J. Scheuer, Grupo de Pesquisa em Tecnologia e Mecaˆnica dos Materiais (GMat), Department of Mechanical Engineering, Technology Center, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil; and A.D. Schneider, L.S. Do
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