Enhancing the oxygen evolution activity of nitrogen-doped graphitic carbon shell-embedded nickel/nickel oxide nanoparticles by surface dissolution†
The lack of well-performing, atom-economic, earth-abundant, transition metal electrocatalysts for the oxygen evolution reaction (OER) in water electrolysers and rechargeable metal–air batteries remains an impediment for their ubiquitous application. Accordingly, nickel oxide has attracted attention as a potential OER catalyst, but its inferior catalytic activity due to the non-participation of its concealed active sites is challenging. Herein, a reported nitrogen-doped graphitic carbon shell-embedded nickel nanoparticle electrocatalyst (Ni-D-700) was investigated to enhance its oxygen evolution activity via the surface dissolution method. This method, which is widely used for dealloying bimetallic nanoparticles to improve their activity, was employed to study the effect of leaching and its duration on a monometallic nanoparticle catalyst. The resultant oxide layer formed on the surface of the nickel nanoparticles (Ni0@Ni2+/Ni3+) exhibited outstanding oxygen evolution activity (1.52 V onset potential vs. RHE, 53.4 mV dec−1 Tafel slope and 360 mV overpotential at 10 mA cm−2 current density) and mass activity, much higher than that of the precursor catalyst. This is attributed to the participation of maximum metal/metal oxide interfaces generated in the process of leaching, which otherwise tend to remain subdued, leading to insufficient catalytic activity.