Enhanced Electrocatalytic Activity of Amorphized LaCoO₃ for Oxygen Evolution Reaction

Amorphous inorganic perovskites have attracted significant attention as efficient electrocatalysts due to their unique structural flexibility and good catalytic activity. In particular, the disordered structure and a surface rich in defects such as oxygen vacancies can contribute to the superior electrocatalytic activity of amorphous oxides compared to their crystalline counterpart. In this work, we report the synthesis of LaCoO₃, followed by an amorphization process through urea reduction with tailored modifications. The as-synthesized catalysts were thoroughly tested for their performance in oxygen evolution reaction (OER), Remarkably, the amorphous LaCoO₃ synthesized at 450 °C (referred to as LCO-4) exhibits excellent OER catalytic activity. At an overpotential of 310 mV, it achieved a current density of 10 mA/cm^-2, exceedingly fast to 1 A/cm^-2 at an overpotential of only 460 mV. Moreover, LCO-4 exhibited several advantageous features compared to pristine LaCoO₃ and LaCoO₃ amorphized at other two temperatures (350 °C, LCO-3, and 550 °C, LCO-5). The amorphized LCO-4 catalyst showed a higher electrochemically active surface area, a key factor in boosting catalytic performance. Additionally, LCO-4 demonstrated the lowest Tafel slope of 70 mVdec^-1, further highlighting its exceptional OER activity. Furthermore, the long-term stability of LCO-4 is notably superior than pristine LaCoO₃ (LCO-P) and the other amorphized samples (LCO-3 and LCO-5). The enhanced catalytic activity of LCO-4 can be attributed to its unique disordered structure, small crystallite size, and higher concentration of oxygen vacancies in the final catalyst.