Engineering oxygen vacancy on nickel-doped iron oxide nanorods as efficient bifunctional electrocatalysts for oxygen evolution and urea oxidation reaction

Background: Finding electrocatalysts to power the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) efficiently, safely, and economically is a challenge in producing energy-saving hydrogen (H₂). Methods: This research aimed to develop a Ni-doped iron oxides nanorod electrode (referred to as Ni/FeO_x NRs@CP) with a large number of defects anchored onto the surface of high-porous carbon paper substrates through hydrothermal and electrodeposition strategies for use as a highly effective electrocatalyst in the OER and UOR processes. By using XRD, FE-SEM and XPS analysis, Ni/FeO_x NRs@CP electrodes were characterized analytically and spectroscopically. Significant findings: As a result of our studies, Ni-doping and enhancing the defect structure of nanocatalysts can increase the performance and efficiency of electrocatalysts. Remarkably, Ni/FeO_x NRs@CP exhibits a minimal overpotential of 242 mV to reach 10 mA/cm² and a Tafel slope of 80.4 mV dec^-1 in a 1 M KOH solution for OER. Interestingly, Ni/FeO_x NRs@CP also exhibits admirable electrocatalytic UOR activity, reaching 50 and 100 mA/cm² versus RHE at low potentials of 1.38 and 1.46 V, correspondingly. Furthermore, using a chronoamperometry test, the stability and durability of Ni/FeO_x NRs was successfully demonstrated during a 60 h and 50 h and 500 cyclic voltammetry cycles for OER and UOR, respectively. The Ni/FeO_x NRs' exceptional catalytic performance and durability may be attributed to two main factors. First, defects in FeO_x NRs reveal more active sites. Second, the introduction of heteroatom doping modifies the electronic structure of the catalyst, thereby improving its ability to facilitate OERs and UORs.