Nanostructured MnWO 4 as a Bifunctional Electrocatalyst for Water Splitting

Abstract

Metal oxides have been considered as photo/electrocatalysts for water splitting because of their compositional and structural flexibility, and consequently, their tunable band gaps. These semiconductor nanomaterials could be used as electrocatalysts for artificial photosynthesis, which mainly includes the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. In this study, we synthesized nanostructured manganese tungstate (MnWO 4 ) using the hydrothermal method as a bifunctional electrocatalyst for HER and OER reactions, which exhibit the Tafel slopes of 160 and 83 mV dec −1 , respectively, in alkaline medium. Prepared nanomaterials were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). We demonstrated an approach to sketch the electronic diagram of nanostructured MnWO 4 by using a combination of UV–Vis diffuse reflectance spectroscopy (DRS) and Mott–Schottky analysis via electrochemical impedance spectroscopy.