Here, we have developed
porous nanostructured Zn electrocatalysts
for CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR), fabricated
by reducing electrodeposited ZnO (RE-Zn) to activate the CO<sub>2</sub>RR electrocatalytic performance. We discovered that the electrochemical
activation environment using CO<sub>2</sub>-bubbled electrolyte during
reducing ZnO in a pretreatment step is important for highly selective
CO production over H<sub>2</sub> production, while using Ar gas bubbling
instead can lead to less CO product of the Zn-based catalyst in CO<sub>2</sub>RR later. The RE-Zn activated in CO<sub>2</sub>-bubbled electrolyte
condition achieves a Faradaic efficiency of CO production (FE<sub>CO</sub>) of 78.5%, which is about 10% higher than that of RE-Zn
activated in Ar-bubbled electrolyte. The partial current density of
CO product had more 10-fold increase with RE-Zn electrodes than that
of bulk Zn foil at −0.95 V vs RHE in KHCO<sub>3</sub>. In addition,
a very high FE<sub>CO</sub> of 95.3% can be reached using the CO<sub>2</sub>-pretreated catalyst in KCl electrolyte. The higher amount
of oxidized zinc states has been found in the high performing Zn electrode
surface by high-resolution X-ray photoelectron spectroscopy studies,
which suggest that oxidized zinc states induce the active sites for
electrochemical CO<sub>2</sub>RR. Additionally, in pre- and post-CO<sub>2</sub>RR performance tests, the carbon deposition is also significantly
suppressed on RE-Zn surfaces having a higher ratio of oxidized Zn
state
