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

Abstract

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 (OV) metal oxides stand out as one of the efficient interfaces for water oxidation, nevertheless, the influence of volume of OV 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 OV to boost the kinetics of OER and HER. Here, dopamine was used to introduce the N-doped carbon and OV defects in the NFO simultaneously. Furthermore, the ratio of OV 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-OV-rich achieved current density of 100 mA/cm2 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-OV-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 OV but also discovers their prospects as dual-functional electrocatalyst toward overall water splitting.