Engineering of oxygen vacancies regulated core-shell N-doped carbon@NiFe2O4 nanospheres: A superior bifunctional electrocatalyst for boosting the kinetics of oxygen and hydrogen evaluation reactions

Exploration of low-cost, highly-efficient, robust electrocatalysts is highly necessary to minimize the cell potential of overall water splitting and encourage the practicality of related energy systems. Oxygen deficient (O-V) metal oxides stand out as one of the efficient interfaces for water oxidation, nevertheless, the influence of volume of O-V on their electrocatalytic efficiency has not been described yet. To resolve this issue, we establish a facile and low-temperature protocol for the fabrication of core-shell N-carbon@NiFe2O4 nanospheres (NC@NFO) with precisely controlled O-V to boost the kinetics of OER and HER. Here, dopamine was used to introduce the N-doped carbon and O-V defects in the NFO simultaneously. Furthermore, the ratio of O-V can be tuned by the simply varying the reaction time, thus the number of active spots and the catalytic performance has been tuned. By virtue of its unique core-shell nanostructure, larger specific surface area, abundant oxygen vacancies, and excellent synergistic effect of N-carbon and NFO, the NC@NFO-O-V-rich achieved current density of 100 mA/cm(2) at a very low overpotential of 230 and 200 mV for OER (Tafel slope 42 mV/dec) and HER (Tafel slope 59.6 mV/dec), respectively, superior than most stated noble/non-noble metal-based catalysts. Also, NC@NFO-O-V-rich exhibited an exceptional overall water splitting performance with low driving voltage of >= 1.45 V, current density of 10 mA cm(-2) has achieved at a very low cell voltage of 1.47 V in 1 M KOH with insignificant activity deterioration over 12 h, which is among topmost activities described. Present work not only provides a novel and facile technique to construct N-doped carbon decorated metal oxides with abundant O-V but also discovers their prospects as dual-functional electrocatalyst toward overall water splitting.