Semiconductor atom doping in heterotrimetallic pentlandite electrocatalyst for non-noble metal alkaline water electrolysis Mohamed Barakat Zakaria Mohamed 1,2 and Ulf-Peter Apfel 1,3 1 Ruhr University of Bochum, Germany, 2 Tanta University, Egypt, 3 Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT, Germany Material doping with foreign elements is a powerful method to tune their electrocatalytic properties [1] . Doping can improve the electrical conductivity and increase the number as well as intrinsic activity of active sites [2] . In this context we demonstrate engineering of inorganic material composed of transition heterotrimetallic-rich pentlandite (Fe 3 Co 3 Ni 3 S 8 (FCNS)) doped with silicon (FCNSSi) as a bifunctional catalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) towards the overall electrochemical water splitting( Figure 1 ). . The electrochemical measurements reflect the improved OER performance of FCNSSi electrode in 1.0M KOH solution and HER in 0.5M H 2 SO 4 due to silicon doping. DFT calculations further confirm that oxidation of the FCNSSi surface during OER significantly adjusts the binding energies of the intermediates on the surface, which weakened the *OH, *O and *OOH adsorption energies. Meanwhile it suggests that Si doping in FCNS enhances the hydrogen adsorption activity of all sites, where the global minimum energy of hydrogen adsorption on each type of metal site tends to be much closer to zero. A two-electrode zero-gap cell assembly reveals the durability of our catalyst at elevated current density of 500 mA cm -2 toward sustainable alkaline water electrolysis.
Figure 1 Schematic illustration for the synthetic pathway of silicon-doped heterotrimetallic pentlandites for the overall electrochemical water splitting References 1. Smialkowski, et al. Chem. Commun. 2019 , 55, 8792; Mohamed, et al. ACS Appl. Mater. Interfaces 2021 , 13, 34043. 2. Mohamed et al. iScience 2022 , 25, 105148; ACS Appl. Mater. Interfaces 2020 , 12, 40186.
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