A comparative study of electrocatalytic performance of metal molybdates for the water oxidation

Binary mixed oxides of molybdenum and a metal of the first-row transition metals with compositional formulae, MMoO4 (where M = Cr, Fe, Mn, Co, Ni, Cu or Zn), were prepared by a microwave-assisted co-precipitation method and their electrocatalytic activities have been investigated for oxygen evolution reaction (OER) in 1 M KOH. Materials were characterized for structural and electrocatalytic surface properties using FT-IR, XRD, TEM, BET, XPS, cyclic voltammetry (CV) and anodic Tafel polarization techniques. The crystallite size of oxides ranged between ∼17 and ∼41 nm. For electrochemical studies, oxides obtained in powders form were produced in the thin-film form on the pretreated glassy carbon (GC) support. It has been observed that among electrocatalysts investigated, the CoMoO4/GC electrode was the greatest OER active while that the MnMoO4/GC electrode was the least active. The OER produced low Tafel slopes, ∼36, ∼43 and ∼46 mV respectively on FeMoO4, CoMoO4 and CuMoO4 while it showed the higher Tafel slopes on CrMoO4(∼57 mV), NiMoO4(∼71 mV) and MnMoO4 (∼89 mV).