Heterostructured Nickel‐Cobalt Selenide Immobilized onto Porous Carbon Frameworks as an Advanced Anode Material for Urea Electrocatalysis

Abstract

Transition-metal selenides based materials have recently aroused an increasing consideration in the field of energy reservation and conversion owing to their good electrochemical performance and low synthetic cost. Herein, multi-walled carbon nanotubes supported binary nickel cobalt selenide composite (NiÀ CoÀ Se/CNT) was prepared by a one-pot-hydrothermal method using hydrazine ions that enables the selenium to diffuse and react with the Ni-and Co-cations to form NiÀ CoÀ Se with a stable nanostructure onto the outer walls of the CNT platforms due to the coordination interaction between the metallic cations and surface oxygen-containing group of the conductive scaffolds. The electrochemical performances for urea oxidation reaction (UOR) are accessed in an alkaline medium by cyclic voltammetry (CV), chronopotentiometry (CA), and electrochemical impedancespectroscopy (EIS) tests. The asprepared NiÀ CoÀ Se/CNT hybrid presents an excellent electrocatalytic activity in terms of current density and onset potential due to synergistic effects of tubular CNT scaffolds, additional Co active sites, and electrochemically active NiOOH layer. The CNTs support markedly enhanced the electrocatalytic properties by providing a rapid mass transport for UOR because of their porous network architectures with a robust adhesion to the NiÀ CoÀ Se nanocrystals. Thus, the synthetic methodology synthetic methodology adopted here is entirely effective for constructing various metal selenide compounds in future.

Carbon Anchored Epitaxially Grown Nickel Cobalt‐Based Carbonate Hydroxide for Urea Electrooxidation Reaction with a High Activity and Durability

“…Moreover, the performance of pure NiCo CHs was also tested under similar conditions. Both catalytic layers exhibit redox peaks ascribed to the redox reactions of Ni 2+ /Ni 3+ and Co 2+ /Co 3+ /Co 4+ . It is worth to note that the redox peaks of C−NiCo CHs catalyst are much larger than those of mixed NiCo CHs, implying that the composite possesses a higher electrochemical activity.…”

“…Figure B shows the CVS of multicomponent C−NiCo CHs and mixed NiCo CHs catalysts in 1 M KOH aqueous solution with 0.33 M urea at 10 mVs −1 . Noticeably, the current density of both electrodes in the anodic branch could be boosted as a result of urea electrocatalysis by the redox cycling between Ni 3+ /Ni 2+ and Co 2+ /Co 3+ /Co 4+ at the catalyst/electrolyte heterointerfaces . A slight current peak can be clearly seen in the cathodic sweep, demonstrating the transformation of unreacted NiOOH species into inactive Ni(OH) 2 .…”

“…On the other hand, previous studies declared that cobalt ions also participate in the electrocatalysis process of urea, but with a humble activity originated from the occurrence of Co 4+ /Co 3+ active sites . Impressively, the porous features of the designated C−NiCo CHs composite with multiple open spaces among the adjoining nanorods ensure a facile release of formed gasses, resulting in better kinetics.…”

“…In fact, the catalysis of urea with a higher oxidation state of nickel is much favorable than Ni 2+ (Figure S8B). In addition, the cobalt doping causes structural defects and edge sites, which enable abundant electrocatalytic sites for UOR …”

Metal‐Organic Framework Derived Ni2P/C Hollow Microspheres as Battery‐Type Electrodes for Battery‐Supercapacitor Hybrids

“…This is characteristic for the BSH, which agrees well with the Randles‐Sevcik equation [Eq. ] …”