Development of Highly Active Bifunctional Electrocatalyst Using Co3O4 on Carbon Nanotubes for Oxygen Reduction and Oxygen Evolution

Replacement of precious platinum catalyst with efficient and cheap bifunctional alternatives would be significantly beneficial for electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and the application of these catalysts in fuel cells is highly crucial. Despite numerous studies on electrocatalysts, the development of bifunctional electrocatalysts with comparatively better activity and low cost remains a big challenge. In this paper, we report a nanomaterial consisting of nanocactus-shaped Co3O4 grown on carbon nanotubes (Co3O4/CNTs) and employed as a bifunctional electrocatalyst for the simultaneous catalysis on ORR, and OER. The Co3O4/CNTs exhibit superior catalytic activity toward ORR and OER with the smallest potential difference (0.72 V) between the Ej10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\boldsymbol{E}}}_{{{\boldsymbol{j}}}_{{\bf{10}}}}$$\end{document} (1.55 V) for OER and E1/2 (0.83 V) for ORR. Thus, Co3O4/CNTs are promising high-performance and cost-effective bifunctional catalysts for ORR and OER because of their overall superior catalytic activity and stability compared with 20 wt% Pt/C and RuO2, respectively. The superior catalytic activity arises from the unique nanocactus-like structure of Co3O4 and the synergetic effects of Co3O4 and CNTs.