Abstract
Developing an efficient and cost-effective electrocatalyst for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of paramount importance for designing metal-air batteries and water electrolyzers. Herein, we present an economical approach for the synthesis of a bifunctional electrocatalyst consisting of cobalt-chromium nanostructures entrapped in a graphene tube doped with nitrogen (CoCr@NGT). The graphene tube is of a large size (cross-sectional diameter ∼ 100 nm) with a wall thickness of more than 10 graphene layers. The Cr alloying with the entrapped Co in the NGT drastically enhanced both the HER and OER performance with a low overpotential (η) and better current density along with long-term durability. Hence, CoCr@NGT can be used as a total alkaline water electrolyzer as both an anode and cathode catalyst delivering a current density of 10 mA/cm2 at around 1.58 V for a long period of time competing with the state-of-the-art combination of Pt-C and RuO2. The electrochemical performance strongly depends on the Cr due to its corrosion resistance capability and improved catalytic sites, which leads to long-term stability and very high activity, respectively.
