Ruthenium and palladium oxide promoted zinc oxide nanoparticles: Efficient electrocatalysts for hydrazine oxidation reaction

Development of highly catalyzing electrode materials for hydrazine electrooxidation reaction (HzOR) demands a judicious assortment of intrinsically active candidates, precise engineering of electrodes for enhancement of active sites and building of electronically conductive structures. Herein, we report the novel, innovative and robust heterogeneous electrocatalysts for HzOR for ultimate hydrogen generation and their applicability in direct hydrazine fuel cell (DHFC). The presented catalysts comprised of ZnO microparticles supported on γ-Al₂O₃ with different weight percentages (10, 20, 30, 40 wt/wt%). Binary catalyst i.e. 20% ZnO/Al₂O₃ displayed the maximum catalytic output towards HzOR, so it is chosen to further combine with RuO₂ and PdO to investigate a promoted and enhanced oxidation output. Ternary metal oxide catalysts i.e. RuO₂-ZnO/Al₂O₃ and PdO-ZnO/Al₂O₃ with varied contents of RuO₂ and PdO (0.1, 0.5 and 1 wt/wt%) are prepared via co-impregnation method. X-Ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled energy dispersive spectroscopy (SEM-EDS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are the techniques employed for physio-chemical characterization of samples. Among all the investigated catalysts, 1% PdO-ZnO/Al₂O₃ produced the most catalyzing behavior toward HzOR owing to its largest diffusion coefficient (50.0 × 10⁻⁶ cm² s⁻¹), highest current density (5.2 mA cm⁻²) and high ECSA (0.23 cm²). The catalysts showed sufficient reproducibility and stability by scanning multiple cycles and testing similar electrodes after different time intervals. This is the first study of hydrazine electrooxidation protocol employing RuO₂ and PdO promoted γ-alumina supported ZnO structured electrocatalysts.