One-Step Eco-Friendly and Ultrasonic Fabrication of Bimetallic Co/Ni-MOF for Improved Efficiency in Overall Water Splitting

The development of efficient and stable bifunctional electrocatalysts for the overall water splitting process is crucial for addressing the energy crisis and environmental challenges. This paper presents the synthesis of isomorphic MOFs, TIT-3-M (M = Co or Ni), through various methods, including hydrothermal synthesis (HS), stirring synthesis (SS), and ultrasonic-assisted synthesis (US), using 4,4 ',4 '-tris(aminobenzoic acid) (H3NTB) and 1,3-bis(4-pyridyl)propane (1,3-BPP). Specifically, the bimetallic material TIT-3-CoNi (US) was synthesized in a 1:1 ratio in an aqueous medium via ultrasonic-assisted method. This material exhibited a current density of 10 mA cm-2 at low overpotentials of 0.79 V for the hydrogen evolution reaction (HER) and 1.99 V for the oxygen evolution reaction (OER). Additionally, an overall water splitting device was assembled using TIT-3-CoNi(US) @NS and TIT-3-CoNi(US)@NS as the anode and cathode, respectively, under alkaline conditions, achieving a current density of 10 mA cm-2 at a cell voltage of 1.37 V. Density functional theory (DFT) calculations indicated that the fixed potential reaction step (PDS) involved the generation of Co active sites (O2) and Ni active sites (O*), corresponding to overpotentials of 0.63 and 0.67 V, respectively. The results suggest that Co is the preferred electrochemical active site for OER. This work paves the way for the development of advanced catalysts with enhanced performance for significant industrial processes, such as water electrolysis or fuel cell technology.