Spherical Ni/NiO nanoparticles decorated on nanoporous carbon (NNC) as an active electrode material for urea and water oxidation reactions

Herein, we report a chemical method for scalable synthesis of spherical Ni/NiO nanoparticle-decorated nanoporous carbon (NNC) based electrocatalytic system using a simple and easy chemical method with ultra-high activity towards urea electrooxidation. Morphological analysis by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) confirms the formation of Ni/NiO NPs on highly nanoporous carbon with an average size of ∼50 nm. X-ray diffraction (XRD) confirms NNC with a face-centred cubic (FCC) crystal structure. Ni/NiO NPs intercalated with nanoporous carbon exhibited the best electrocatalytic performance towards urea oxidation with an ultra-low onset potential of ∼0.33 V vs. SCE, and faster electrokinetic mechanism confirmed from Tafel slope (∼45 mV dec-1), EIS Rct (∼6.98 Ω), and long term durability for 7 h at 10 mA cm-2 with high CO poisoning tolerance. This work affords noble metal-free electrocatalysts for novel appliances and remarkable potential for urea determination, hydrogen generation, real-time water remediation, and energy conversion.

Interface Engineering of SRu-mC3N4 Heterostructures for Enhanced Electrochemical Hydrazine Oxidation Reactions

Hydrazine oxidation in single-atom catalysts (SACs) could exploit the efficiency of metal atom utilization, which is a substitution for noble metal-based electrolysers that results in reduced overall cost. A well-established ruthenium single atom over mesoporous carbon nitride (SRu-mC3N4) catalyst is explored for the electro-oxidation of hydrazine as one of the model reactions for direct fuel cell reactions. The electrochemical activity observed with linear sweep voltammetry (LSV) confirmed that SRu-mC3N4 shows an ultra-low onset potential of 0.88 V vs. RHE, and with a current density of 10 mA/cm2 the observed potential was 1.19 V vs. RHE, compared with mesoporous carbon nitride (mC3N4) (1.77 V vs. RHE). Electrochemical impedance spectroscopy (EIS) and chronoamperometry (i-t) studies on SRu-mC3N4 show a smaller charge-transfer resistance (RCt) of 2950 Ω and long-term potential, as well as current stability of 50 h and 20 mA/cm2, respectively. Herein, an efficient and enhanced activity toward HzOR was demonstrated on SRu-mC3N4 from its synergistic platform over highly porous C3N4, possessing large and independent active sites, and improving the subsequent large-scale reaction.