In Situ Formation of Surface-Induced Oxygen Vacancies in Co9S8/CoO/NC as a Bifunctional Electrocatalyst for Improved Oxygen and Hydrogen Evolution Reactions

Creating oxygen vacancies and introducing heterostructures are two widely used strategies in Co-based oxides for their efficient electrocatalytic performance, yet both strategies have rarely been used together to design a bifunctional electrocatalyst for an efficient overall water splitting. Herein, we propose a facile strategy to synthesize oxygen-defect-rich Co9S8/CoO hetero-nanoparticles with a nitrogen-doped carbon shell (ODR-Co9S8/CoO/NC) through the in situ conversion of heterojunction along with surface-induced oxygen vacancies, simply via annealing the precursor Co3S4/Co(OH)(2)/ZIF-67. The as-prepared ODR-Co9S8/CoO/NC shows excellent bifunctional catalytic activities, featuring a low overpotential of 217 mV at 10 mA cm(-2) in the oxygen evolution reaction (OER) and 160 mV at 10 mA cm(-2) in the hydrogen evolution reaction (HER). This performance excellency is attributed to unique heterostructure and oxygen defects in Co9S8/CoO nanoparticles, the current work is expected to offer new insights to the design of cost-effective, noble-metal-free electrocatalysts.

Automated summary

The study proposes a facile strategy to synthesize oxygen-defect-rich Co9S8/CoO hetero-nanoparticles with a nitrogen-doped carbon shell, exhibiting excellent bifunctional catalytic activities with low overpotentials in both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The outstanding performance is attributed to the unique heterostructure and oxygen defects in the Co9S8/CoO nanoparticles, offering new insights for designing cost-effective, noble-metal-free electrocatalysts.