Phosphorus and Sulfur Co-Doped Cobaltous Oxide Synthesized by an Inorganic-Salt-Assisted Method: Reaction Mechanism and Electrocatalytic Application.

Abstract

An inorganic-salt-assisted synthesis of non-metallic heteroatom (phosphorus and sulfur) co-doped cobaltous oxide (P/S-CoO) has been reported. Potassium sulphate (K2 SO4 ) was used as inorganic source of sulfur (S), while triphenyl phosphine (PPh3 ) was used as phosphorus (P) source. A stepwise mechanistic investigation into the doping process revealed that the decomposition of PPh3 triggered the release of both the elemental sulfur and phosphorus because of the reducing reaction environment. The transformation of cobalt-PPh3 complex into cubic cobalt (II) oxide along with the successful co-doping (P and S) was achieved by high temperature calcination at 800 °C but preserved the bulk CoO crystalline structure. The as synthesized P/S-CoO demonstrated an unprecedented enhancement on the oxygen evolution activity compare to that of pristine CoO with the current density of 10 mA/cm2 at the overpotential of 293 mV in 1.0 M KOH electrolyte and profound stability at different current densities.