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.