Dynamic response to fluctuating input of Nb:Ti:N film modified Ti bipolar plates for proton exchange membrane water electrolyser

The potential application of renewable energy sources such as wind power and photovoltaics in hydrogen production from water electrolysis has driven the development of bipolar plates . Combined with theoretical conductivity calculations and electrode potential-pH diagram constructions, a novel Nb :Ti:N film for bipolar plates is innovatively designed with excellent electrical conductivity and corrosion resistance , as well as high thermal and chemical stability. The Nb and N elements improve the electronic delocalisation effect and transport capacity of Ti and TiO 2 , and the interfacial contact resistance of the Nb:Ti:N film modified Ti bipolar plates has been decreased to 3.27 mΩ cm 2 at 1.4 MPa, with an enhancement of electrical conductivity by about 86 %. At 0 < pH < 7, both Ti metal and Nb metal present good stability and the passivation zone is mainly in the form of TiO 2 and Nb 2 O 5 . At 1.8 V (vs. Ag/AgCl), the corrosion resistance of Nb metal is better and the Nb oxide formed by passivation of Nb metal prevents the dissolution of Ti substrate into TiO 2+ and (TiO 2 ) 2+ ions. Moreover, periodic triangle and square wave polarization potentials have been applied to simulate wind and photovoltaic power input. By evaluating the durability and dynamic response characteristics of the bipolar plates under fluctuating voltage input conditions, it can be concluded that the high potential promotes the passivation behavior of Nb metal in Nb:Ti:N films, which results in a fast response to current fluctuations caused by fluctuating potentials. • Theoretical electrical conductivity and E-pH diagram are predicted. • Nb:Ti:N film enhances interfacial conductivity and corrosion resistance . • Upper limit of potential is the main cause of bipolar plate failure. • Passivation products of Nb components protect Ti substrate from dissolution.