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.