Unravelling the Growth Mechanism of Local Entropy Tailored Intermetallic Pd₃Ni Exhibiting Tetrafunctional Activity in...

Designing a multifunctional electrocatalyst is increasingly in demand. This work deals with successful solution phase synthesis of an ordered compound of Pd and Ni, Pd₃Ni, which is assumed to be difficult as almost no adjacent elements in the same group form intermetallic compounds. Pd₃Ni is a highly efficient and electrochemically stable material for tetrafunctional activity, in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and ethanol oxidation reaction (EOR), which are involved in both fuel cells and water electrolyzers. Extensive ex situ and in situ characterization has revealed the robustness of this material and the reaction mechanism in different electrochemical reactions. The "local entropy tailoring" reflects the reduced configurational entropy associated with the ordered Pd₃Ni lattice relative to the alloy, as evidenced by differential scanning calorimetry, enabling site-specific structural stability. This material has shown promising activity in a proton exchange membrane water electrolyzer and a high temperature fuel cell. The tuned surface of the intermetallic compound has enhanced C-C cleavage in ethanol molecules allowing the sluggish 12e^- transfer process, and the compound has shown very high stability for >80000 cycles of alkaline HER. The role of pH and potential has been explored in retaining the ordered phase of the intermetallic compound. Tetrafunctionality and its extensive exploration under different reaction conditions have been exhaustively evaluated in this work.