Selenium-doped copper oxide nanoarrays: Robust electrocatalyst for the oxygen evolution reaction with ultralow overpotential

The oxygen evolution reaction (OER) is the key anodic reaction in electrochemical water splitting. OER is a four-electron process with sluggish reaction kinetics. RuO2 and IrO2 are the benchmark catalysts for OER. Thus, finding a low-cost, earth-abundant, and stable electrocatalyst for OER is a big challenge. In this work, we report OER over Se-CuO/CF nanoarrays with an ultralow overpotential of 440 mV (at 50 mA/cm2 current density). Se-CuO/CF nanoarray has a TOF of 0.05 s−1 at 300 mV. The catalyst showed consistent OER performance upto1000 cycles run over a period of 10 h. The OER performance of Se-CuO/CF nanoarrays was compared with RuO2/CF catalyst and the overpotential for RuO2/CF nanoarray was only 10 mV lower than Se-CuO/CF 50 mA/cm2 current density. Se-CuO/CF nanoarray showed 50 mV lower overpotential than the state of the art RuO2/CF catalyst at a current density of 100 mA/cm2. The Tafel slope of Se-CuO/CF is 21 mV/decade lower compared to RuO2/CF suggesting faster reaction kinetics of Se-CuO/CF. The electrochemical surface area and the conductivity were increased upon doping Se into CuO/CF nanoarrays which can be attributed to enhanced OER performance of the Se-CuO/CF nanoarrays.