Morphology and strain control of hierarchical cobalt oxide nanowire electrocatalysts via solvent effect

Designing highly efficient and low-cost electrocatalysts for oxygen evolution reaction is important for many renewable energy applications. In particular, strain engineering has been demonstrated as a powerful strategy to enhance the electrochemical performance of catalysts; however, the required complex catalyst preparation process restricts the implementation of strain engineering. Herein, we report a simple self-template method to prepare hierarchical porous Co₃O₄ nanowires (PNWs) with tunable compressive strain via thermal-oxidation-transformation of easily prepared oxalic acid-cobalt nitrate (Co(NO₃)₂) composite nanowires. Based on the complementary theoretical and experimental studies, the selection of proper solvents in the catalyst preparation is not only vital for the hierarchical structural evolution of Co₃O₄ but also for regulating their compressive surface strain. Because of the rich surface active sites and optimized electronic Co d band centers, the PNWs exhibit the excellent activity and stability for oxygen evolution reaction, delivering a low overpotential of 319 mV at 10 mA·cm⁻² in 1 M KOH with a mass loading 0.553 mg·cm⁻², which is even better than the noble metal catalyst of RuO₂. This work provides a cost-effective example of porous Co₃O₄ nanowire preparation as well as a promising method for modification of surface strain for the enhanced electrochemical performance. [Figure not available: see fulltext.]