MoO 2 as a Propitious “Pore-Forming Additive” for Boosting the Water Oxidation Activity of Cobalt Oxalate Microrods

The electrocatalytic oxygen evolution reaction (OER) demands an efficient catalyst with low overpotential, rapid kinetics, and long-term stability. Herein, we demonstrate the activity of molybdenum oxide (MoO 2 )-embedded cobalt oxalate (CoC 2 O 4 ·2H 2 O) nanostructures for the OER process. The excellent performance of the microrod-like MoO 2 /CoC 2 O 4 ·2H 2 O composite is reflected in just 330 mV overpotential for 10 mA/cm geo 2, low Tafel slope (78 mV/dec), 90% faradaic efficiency, and 24 h stability in 1.0 (M) KOH. The as-prepared electrocatalyst requires a significantly lower overpotential wrt CoC 2 O 4 ·2H 2 O. Incorporation of MoO 2 elegantly modified the textural property, such as surface area and porosity, of the as-prepared material. Furthermore, MoO 2 /CoC 2 O 4 ·2H 2 O was found to follow the proton-decoupled electron-transfer mechanism for electrocatalyzing OER. Postcatalytic characterization revealed the electrochemical transformation of a one-dimensional (1-D) MoO 2 /CoC 2 O 4 ·2H 2 O microrod into a sheetlike two-dimensional α-Co(OH) 2 /CoOOH during alkaline OER. Interestingly, postcatalytic X-ray photoelectron spectroscopy, inductively coupled plasma, and energy-dispersive X-ray spectroscopy analyses suggest MoO 2 etching from the material, leading to exposure of a higher number of electrochemically active sites that otherwise lay inactive because of their presence in the bulk. Both CoC 2 O 4 ·2H 2 O- and MoO 2 /CoC 2 O 4 ·2H 2 O-integrated 1-D nanostructures showed an ∼0.01 s –1 turnover frequency value at 400 mV overpotential. We believe that the enhancement in geometrical electrocatalytic activity is not due to the direct participation of MoO 2 in catalysis but due to its electrochemical etching, which makes a higher number of catalytically active sites accessible to the electrolyte. This study conveys the in situ electrochemical activation strategy through etching of pore additive for the alkaline OER process.