In situ soft XAS for investigation of PAni and PAni/ions composites as an inhibitor of hydrogen evolution reaction in flow redox batteries

• Grant number: 24/12856-1
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• Start date: September 01, 2024
• End date: August 31, 2025
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Evaldo Jose Corat
• Grantee: Suelem Soares dos Santos
• Supervisor: Christina Roth
• Host Institution: Instituto Nacional de Pesquisas Espaciais (INPE). Ministério da Ciência, Tecnologia e Inovação (Brasil). São José dos Campos , SP, Brazil
• Institution abroad: University of Bayreuth, Germany
• Associated to the scholarship: 22/07225-7 - Study of EDLC supercapacitors for applications in capacitive deionization, BP.DD

Abstract

Carbonaceous materials are used for electrochemical applications due to their unique properties. However, they catalyze the parasitic hydrogen evolution reaction (HER) in aqueous electrolytes, which causes problems such as water loss and reaction competition. Electrode surface modifiers are often used to improve pseudocapacitance and reduce HER. Polyaniline (PAni) is a conductive polymer that can be applied as surface modified due to its conductivity, chemical resistance, and environmental stability. A recent study shows that the PAni with Pb electro adsorbed on a carbon fiber (CF) surface was applied with success to prevent HER in lead-acid batteries (LAB). HER is also a problem on the cathodic part of Vanadium redox flow batteries (VRFBs) and the ability of PAni to adsorb different metallic ions allows the investigation of CF/PAni modified with other elements, as In and Bi, for HER inhibition in VRFBs. Besides the electrochemical behavior, the adsorption of ions on PAni structure can affect its structure and it was shown in the CF/PAni/Pb composite where the coordination between Pb2+ and the PAni chains prevented the reduction of the emeraldine salt to leucoemeraldine. Soft X-ray absorption spectroscopy (XAS) measurements while the electrochemical measurements are performed, and density functional theory (DFT) can help us understand in detail the effect of the adsorption of ions on PAni structure. Thus, this investigation aims to adapt the PAni deposition and ions (Pb, In, Bi) adsorption method in the in situ electrochemical cell to investigate the electrochemical behavior of materials for HER inhibition on VRFB using in situ soft-XAS and DFT simulations.