Surface evolution of Zn doped-RuO2 under different etching methods towards acidic oxygen evolution

Abstract

The exact role of atom etching in the surface properties and electrocatalytic oxygen evolution reaction (OER), which is a dynamic system, still remains unclear. Hence, to gain a deeper insight into the structure–activity relationship of acidic OER catalysts, we fabricated Zn-doped RuO₂ (Zn–RuO₂) nanospheres to trace their structure evolution by actively strengthening the etching process of Zn–RuO₂ during the catalytic process. We found that compared to pure pickling (C–Zn–RuO₂), in situ electrochemical etching (E–Zn–RuO₂) enables a more thorough surface evolution of the Ru center, ensuring superior OER activity through well-dispersed nanocrystals, more defects and an appropriate electronic structure. The resulting E–Zn–RuO₂ only requires 190 mV at a current density of 10 mA cm⁻². Furthermore, E–Zn–RuO₂ underwent a pre-oxidation and irreversible surface reconstruction to form a stable active surface, thus it can steadily operate for 60 h at the constant 10 mA cm⁻², obviously surpassing C–Zn–RuO₂ (15 h). Here, Zn atoms can not only promote the change of electronic structure during electrical activation, but they also elevate the OER activity in acidic media. Theoretical calculation confirms that the Ru–O band has been shortened after Zn doping, which is conducive to a longer lifetime. Besides, the water oxidation proceeds via a new mechanism, where the deprotonation of the –OH species can stabilize the –OO groups on the Ru sites.