Unravelling the operando structural and chemical stability of rare earth metals co-doped CeO2-based electrocatalysts for oxygen evolution reaction

Abstract

Highly efficient, abundant, and long-lasting electrocatalysts for oxygen evolution will be essential to industrial hydrogen production via water splitting. Hydrogen has emerged as an alternative to conventional fossil fuels, a sustainable and green energy source. Water electrolysis via co-doped metal oxides has been employed to reduce energy loss during electrochemical oxygen evolution reactions (OER), a great alternative to noble-metal-derived electrocatalysts. In the present work, Nd-dopped CeO2 (CeNdO2) nanostructures co-doped with rare earth metals are fabricated via sol-gel technique and analysed via state-of-the-art methods, focusing on structural, morphological, elemental, electrical and electronic capabilities. All fabricated samples were coated on nickel foam (NF) and fluorinated tin oxide (FTO) substrate for electrochemical splitting of water in a 1.0 M KOH. The Pr/Nd co-doped CeO2 grown on NF demonstrates high electrochemical activity with a significantly reduced OER over-potential of around 274 mV, Tafel slope around 84 mV/dec, and increased electrochemical surface area. This co-doped metal oxide nanostructure causes interactions with oxy-radicals (confirmed from XPS and Raman), which are thought to be source of easy charge transport and decrease overpotential. The least charge transfer resistance of Pr-doped CeNdO2/NF presented excellent electroactivity due to reduced polarization resistance between electrolyte and catalyst material. Additionally, for a practical water electrolysis system, the high stability of Pr doped CeNdO2/NF electrode was exposed by continuous cyclic voltammetry sweeps of electrolysis up to 1500 cycles. This work reveals a synergistic effect between metal atoms (Ce, Nd, and Pr) on nickel foam substrate, which is mainly responsible for electron transfer and well-balanced kinetics under beginning conditions.