Three-dimensional tetsubo-like Co(OH)2 nanorods on a macroporous electrically conductive network as an efficient electroactive framework for the hydrogen evolution reaction

Conducting the hydrogen evolution reaction (HER) in an alkaline environment using a non-precious transition metal catalyst with high efficiency is challenging. Here, we report excellent HER activity achieved using three-dimensional (3D) tetsubo-like Co(OH)2 nanorods on a macroporous electrically conductive network (MECN) synthesized by a hydrothermal method. This unique framework comprises three levels of porous structures, including a bottom-ordered MECN substrate, an intermediate layer of vertically porous Co(OH)2 nanowires with a mean diameter of 100 nm and length of about 2 μm, and outmost Co(OH)2 nanosheets (≈20 nm). The 3D array structure with a large aspect ratio provides a large specific surface area and exposes more active sites to catalyze electrochemical reactions at the electrode–electrolyte interface. Compared with Co(OH)2 nanosheets on an MECN and foamy Co(OH)2 on an MECN structure, the synthesized architecture has excellent HER catalytic reactivity, including a low potential of −69.2 mV vs. RHE, a cathodic current density of 10 mA cm−2, a small Tafel slope of 61.9 mV dec−1, a high current density, and robust catalytic stability in 1 M KOH, and is promising in HER applications.