Highly Active Core–Shell Carbon/NiCo<inf>2</inf>O<inf>4</inf> Double Microtubes for Efficient Oxygen Evolution Reaction: Ultralow Overpotential and Superior Cycling Stability

Abstract

Developing highly efficient electrocatalysts with earth abundant elements for oxygen evolution reaction (OER) is a promising way to store light or electrical energy in the form of chemical energy. Here, a new type of electrocatalyst with core–shell carbon/NiCo2O4 double microtubes architecture is successfully synthesized through a hydrothermal method combined with the calcination process with wet tissues as the template and carbon resource. The outer NiCo2O4 nanosheet arrays contain abundant defects, which come from reduction of the carbon in wet tissues. This indicates that carbon is a very excellent defect inducer. The inner carbon microtubes can act as the robust structure skeleton and these core–shell double microtubes provide abundant diffusion channels for oxygen and electrolyte, both of which contribute to improving the stability by avoiding damage to the electrode from produced O2 bubbles and the collapse of the outer NiCo2O4 microtubes. Electrochemical results show that the electrode, core–shell carbon/NiCo2O4 double microtubes loaded on carbon cloth, exhibits prominent electrocatalytic activity with an overpotential of only 168 mV at 10 mA cm−2 and a Tafel slope as low as 57.6 mV dec−1 in 1.0 mol L−1 KOH. This new type of electrocatalyst possesses great potential in water electrolyzers and rechargeable metal–air batteries.