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.