Corrosion resistance of functionally graded Niobium Nitride (NbN) films for application in bipolar plates of PEM-type electrolyzers for green hydrogen generation

• Grant number: 25/04921-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2025
• End date: June 30, 2026
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Principal Investigator: Felipe Carneiro da Silva
• Grantee: João Pedro Calomeni Eletério
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Electrolyzers are devices that produce green hydrogen from the splitting of the water molecule. This hydrogen produced can be used as raw material for decarbonization in various industrial sectors, such as:* In steel manufacturing (replacing coal as a reducing agent);* In glass manufacturing;* In the synthesis of green ammonia (a key component for the production of agricultural fertilizers);* In the production of sustainable fuels (such as synthetic diesel and gasoline, which can also be used for purposes other than the automotive sector, such as the aerospace and maritime sectors);* Used as fuel in PEMFC-type fuel cells.Among the available types of electrolyzers, the PEM (Proton Exchange Membrane Water Electrolyzer - PEMWE) stands out compared to others (Alkaline Water Electrolysis - AWE and Solid Oxide Water Electrolysis - SOWE) due to its high current density (¿ 02 A.cm¿2), rapid response, safety, compactness, and the ability to operate at high pressures (greater than 350 bars). On the other hand, PEM electrolyzers have a high manufacturing cost, primarily due to the materials used in the construction of their structural components. Among these components, bipolar plates account for approximately 50% of the total cost. The required prerequisites for these plates to ensure proper operation of this type of electrolyzer are: good thermal and electrical conductivity, good corrosion resistance, and good mechanical stability.Among the widely produced engineering materials, metallic alloys meet these needs. The scientific literature reports two types of alloys that are used as the base material for bipolar plates in PEMWE: titanium alloys and stainless steels.However, titanium-based bipolar plates have a high manufacturing cost. In the case of stainless steels, although it is one of the most promising materials compared to titanium alloys due to its lower cost, bipolar plates made from this material, when subjected to the anodic environment of an electrolyzer, experience a performance drop due to chemical instability.The scientific objective of this project is to simulate, verify, and evaluate the corrosive behavior of gradient NbN (niobium nitride) thin films deposited on the surface of AA1100 aluminum alloys to simulate the anodic environment (oxygen saturation) of bipolar plates in a PEM electrolyzer.METHODOLOGYThe project will be developed at the Department of Metallurgical and Materials Engineering at the Polytechnic School of USP (EPUSP), particularly in the Metallography Laboratory and the Electrochemical Processes Laboratory (LPE). These laboratories have the necessary infrastructure to carry out the project.During the deposition process, the NbN films will be subjected to a variable flow of N2 (which we are calling a graded film). The N2 flow will be varied throughout the deposition time. The Grid Assisted Magnetron Sputtering (GAMS) technique will be used, and this system is described and presented by Fontana et al. (FONTANA; MUZART, 1999) and was used by the author of this project during the execution of his PhD (SILVA, 2019) and in published articles (SILVA et al., 2020; SILVA F.C.; PRADA, 2020; TUNES et al., 2018).EXPECTED RESULTS AND IMPACTSThe expected results for this project include the comparison and evaluation of the corrosive behavior (through electrochemical tests) of functionally graded NbN thin films on AA1100 aluminum. With these results, it will be possible to better understand the corrosive process in this combination of coatings and aluminum alloys, contributing to science and technology and identifying the best alternative to apply these materials in PEM-type electrolyzers (green hydrogen generation).