Functionalized Carbon Nanotubes Supported 3D Zinc/Cobalt Oxide as an Efficient Electrocatalyst for Oxygen Evolution Reaction

Abstract

In this study, we developed 3D zinc oxide (ZnO) and cobalt oxide (Co 3 O 4 ) supported by functionalized carbon nanotubes (O-CNT) to form a catalyst (ZnO/Co 3 O 4 @O-CNT) for oxygen evolution reaction (OER). The catalyst improved catalytic OER performance with the lowest overpotential of 260 mV to reach 10 mA cm −2 and a small Tafel slope of 79 mV dec −1 , which is smaller than that of ZnO/Co 3 O 4 and O-CNT. The catalyst exhibited fast electron transfer and high electrical conductivity owing to the O-CNT that acted as a conducting support, and the introduction of ZnO synergistically enhanced the OER activity of the synthesized catalyst. The specific activity and turnover frequency of the ZnO/Co 3 O 4 @O-CNT catalyst at an overpotential of 400 mV were 0.130 mA cm −2 and 2.45 s −1 , respectively, which are considerably higher than those of pristine ZnO/Co 3 O 4 (0.024 mA cm −2 , 0.23 s −1 ) and O-CNT (0.012 mA cm −2 , 0.03 s −1 ). The high catalytic performance of the catalyst is attributed to the presence of oxygen functional groups, which induced a high electrochemical surface area, additional active site exposure, fast electron transfer, and enhanced dispersion of the catalyst. Thus, the synthesized ZnO/Co 3 O 4 @O-CNT catalyst can be a good candidate as an alternative to high-cost noble metals for OER performance.