Evaluation of the activity-stability relationship and dynamic equilibrium of the metallic phosphides based on Co, Ni, and Fe to overall water splitting

• Grant number: 22/03455-8
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: September 01, 2022
• End date: August 31, 2023
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Lucia Helena Mascaro Sales
• Grantee: Dyovani Coelho
• Supervisor: Serhiy Cherevko
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Institution abroad: Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN), Germany
• Associated to the scholarship: 21/08614-4 - Electrodeposition of transition metal sulfides and phosphides on 3D electrodes for water splitting, BP.PD

Abstract

The main catalysts used for overall water splitting in alkaline water electrolyzer are based on Ni for hydrogen evolution reaction (HER) and Ni-Co alloys for oxygen evolution reaction (OER); however, they show high overpotentials to these reactions. One promising alternative is the use of catalysts based on non-precious metals such as Ni, Co, and Fe phosphides to overall water splitting. Here, we propose the evaluation of the activity/stability relationship and the dynamic equilibrium of the MeP, where Me = Co, Fe, and Ni or their combinations, catalysts to both reactions, HER and OER. The catalyst will be electrodeposited on Ni, grade 304, and grade 316 stainless steel into electrolyte containing the corresponding CoSO4, NiSO4, FeSO4, Na2PO2, precursors and H3PO4 under a galvanostatic regime. The electrodeposition will be done using an electrochemical scanning flow cell (SFC), aiming at high-throughput electrochemistry, changing the concentrations of the precursors into the electrolyte at each deposition cell spot by autonomous testing procedure. The activity/stability relationship will be studied by SFC on-line with Inductive Coupled Plasma Mass Spectrometry (SFC-ICP-MS) in alkaline and neutral solutions, which allows the study of the catalyst activity and the detection of dissolution events related or not to applied potentials and electrolyte composition. The same experimental apparatus will be used to investigate the dynamic equilibrium of the catalyst after adding small amounts of precursors to the electrolyte. Moreover, the morphology, uniformity, and composition changes of the catalyst will be evaluated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS), before and after the SFC-ICP-MS investigation. The electrochemical properties, overpotential parameters for HER and OER, stability, and charge transfer resistance will be studied by electrochemical techniques. It is expected to estimate the viability of catalysts based on MeP to overall water splitting and opens up a simple and cost-efficient method to produce new-generation catalysts to HER and OER. (AU)