Electrooxidation of ammonia at high-efficiency RuO2-ZnO/Al2O3 and PdO-ZnO/Al2O3 mesoporous catalysts; an innovative strategy towards clean fuel technology

Abstract

Ammonia is an ideal alternative of hydrogen with high hydrogen content and environmental safety but production of hydrogen from ammonia is deterred by developing active and affordable catalysts. Herein, we report PdO and RuO2 promoted ZnO/Al2O3 ternary materials as efficient and robust electrocatalysts towards AEO. Little weight percentages of PdO and RuO2i.e., 0.1 %, 0.5 % and 1 % are added into 20 % ZnO/Al2O3 via co-impregnation method followed by rotatory ball milling to achieve uniform morphology. Prepared metal oxide catalysts exhibited nanocrystallite sizes and mesoporous structure thereby enhancing the electronic and catalytic properties. Adsorption-desorption isotherms and BJH diagrams revealed mesoporous structure of the catalysts with nanosized pores endorsing high surface area. Electroanalytical techniques applied to study AEO using 1 M NH3 showed that the developed materials effectively electro-catalyzed the reaction observed in alkaline medium i.e. 0.1 M KOH. Varying scan rate indicated it as a diffusion controlled process offering high diffusion coefficient. Ternary metal oxides gave the promoted and improved catalytic output displaying high current density “j” (307 µA cm−2 and 742 µA cm−2 at 10 mV s−1) and low charge transfer resistance “Rct” (24.1 and 9.7 kΩ) with RuO2-ZnO/Al2O3 and PdO-ZnO/Al2O3, respectively. These electrochemical possessions are attributed to half-filled d-orbitals of Pd and Ru. In this way, PdO and RuO2 promoted ZnO mixed metal oxide electrocatalysts reported for the first time could be employed to accelerate high-performance efficient energy generating technologies.