Deep eutectic solvent strategy enables an octahedral Ni–Co precursor for creating high-performance NiCo2O4 catalyst toward oxygen evolution reaction

Deep eutectic solvents (DESs) have gained much attention in the fabrication of advanced nanoelectrocatalysts due to their amazing template function. However, their stabilizing function for easily hydrolyzed inorganic nanomaterials is rarely studied. Here, a DES-mediated strategy was reported to synthesize octahedral Ni–Co precursor (NiCo–NH 3 complex), which could be directly transformed into NiCo 2 O 4 nanooctahedrons after thermal decomposition. The NiCo–NH 3 precursor in octahedral shape was achieved with the DES-mediated crystallization in the choline chloride (ChCl)/glycerol. The ChCl/glycerol DES not only tailored the morphology of the as-prepared precursor by template effect but also inhibited its hydrolysis, ensuring the successful fabrication of octahedral NiCo–NH 3 complex precursor with high yield. The NiCo–NH 3 complex precursor was converted to well-defined NiCo 2 O 4 nanooctahedrons, where the calcination temperature and time were explored in detail. It revealed that DES could participate in the conversion process to control the morphology of calcination product. The resultant NiCo 2 O 4 nanooctahedrons demonstrated excellent electroactivity and remarkable durability for oxygen evolution reaction (OER). The present strategy not only offers an efficient OER electrocatalyst but also enriches the approaches of DESs in designing advanced nanocatalysts.