Abstract: The oxygen evolution reaction (OER) is regarded as the bottleneck of electrolytic water splitting. Thus, developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is an ongoing scientific challenge. Herein, hierarchical hollow nanorods assembled with ultrathin mesoporous cobalt silicate hydroxide nanosheets (denoted as CoSi) were successfully fabricated, using the silica nanotube derived from halloysite as a sacrificial template, via a simple hydrothermal method. The resulting cobalt silicate hydroxide nanosheets stack with thicknesses ∼10 nm, as confirmed by transmission electron microscopy. The elaborated nanoarchitecture possesses a high specific surface area (SSA) allowing good exposure to the cobalt active centers exhibiting superior catalytic activity vs analogs synthesized using sodium silicate. Among all as-prepared CoSi samples, those synthesized at 150 °C (CoSi-150) exhibited the minimum overpotential of ∼347 mV at a current density of 10 mA cm^-2. In addition, CoSi-150 also exhibited superior performance against typical cobalt-based catalysts, and its surface hydroxyl groups were beneficial for the enhancement of OER performance. Furthermore, the CoSi-150 showed excellent durability and stability after the 10⁵ s chronopotentiometry test in 1 M KOH. This design concept provides a new strategy for the low-cost preparation of high-quality cobalt water splitting electrocatalysts.

Key words: Halloysite, Cobalt silicate hydroxide, Hollow nanorod, Oxygen evolution reaction, Water splitting, Catalysts