Enhancing Activity and Stability of Cobalt Oxide Electrocatalysts for the Oxygen Evolution Reaction via Transition Metal Doping

Developing highly active and durable electrocatalysts for the oxygen evolution reaction (OER) is of pivotal importance for the widespread deployment of water splitting cells. Co 3 O 4 -based electrocatalysts have been of particular interests due to high OER activity. In the present work, a series of transition metal-doped Co 3 O 4 electrocatalysts have been prepared for systematic investigation of impact of dopants on the activity and durability. For the OER, the addition of dopant improves activity of catalysts, with Sn-doped Co 3 O 4 (Sn-Co 3 O 4 ) showing the best electrocatalytic activity followed by Ni-Co 3 O 4 , Fe-Co 3 O 4 , and Co 3 O 4 (in the order of activity). Highly active Sn-Co 3 O 4 and Ni-Co 3 O 4 reach 10 mA cm −2 at a low overpotential of 0.354 V and 0.360 V, respectively, which is close to Ir/C (0.373 V). The addition of transition metal invokes change of crystallite size of Co 3 O 4 and the overpotential of each catalyst shows a linear relationship with the crystallite size and geometric surface area. The Ni-Co 3 O 4 catalyst exhibits significantly enhanced durability compared to the pure Co 3 O 4 catalyst. Raman spectra and transmission electron microscopy after cycling tests reveal that the incorporation of multivalent Ni cations on the octahedral and tetrahedral sites of spinel structure Co 3 O 4 effectively mitigates surface amorphization of catalysts, thereby enhancing the durability.