Dendrimer-Ni-Based Material: Toward an Efficient Ni-Fe Layered Double Hydroxide for Oxygen-Evolution Reaction

Ni/Fe oxides are among the most widely used catalysts for water splitting. This paper outlines a new approach to synthesize Ni-Fe layered double hydroxides (Ni-Fe LDHs) for oxygen-evolution reaction (OER). Herein, we show that a dendrimer with carboxylate surface groups (generation 3.5) could react with Ni(II) ions to form a precatalyst for OER. During electrochemical OER, this precatalyst converted to Ni-Fe LDH, which is an efficient catalyst toward OER in the presence of Fe(III) ions. The catalyst was characterized by a number of methods and applied for OER using fluorine-doped tin oxide (FTO), Au, Pt, Ni foam, and glassy carbon electrodes. The catalyst shows a current density of 100 mA/cm² on the surface of the Ni foam, using only 297 mV overpotential and with the Tafel slope of 60.8 mV/decade. A current density of 50 mA/cm² on the surface of Au or Pt requires 333 and 317 mV overpotentials, respectively. The slopes of the Tafel plots for the catalyst on Au, GC, and Pt are 52.5, 47.1, and 37.4 mV/decade, respectively. The dendrimer resulted in a large dispersibility and an increase in active sites of Ni-Fe LDH, as well as the formation of Ni-Fe LDH.