Architecting the AuPt alloys for hydrazine oxidation as an anolyte in fuel cell: Comparative analysis of hydrazine splitting and water splitting for energy-saving H2 generation

Abstract

Replacing the kinetically sluggish anodic oxygen evolution reaction (OER) with hydrazine (N2H4) oxidation reaction (HzOR) could be the effective approach for achieving energy-saving hydrogen (H2) fuel production in a water electrolyzer system. Thus, developing the efficient HzOR electrocatalysts, combined with the cathodic H2 evolution reaction (HER) is of vital importance for the high-rate H2 fuel generation as well as for the advancement of a N2H4 fuel cell. Herein, we utilized a facile integrated process of pulsed laser irradiation and sonochemical process to synthesize AuPt alloys by the irradiation of laser to a mixture of Au/Pt solution in methanol/DI water in varied proportions. The AuPt alloy plays a key role in the chemisorption of N2H4 on its surface, forming a dative bond involving electrons of the lone pair of nitrogen in N2H4 and empty orbitals of Pt in the alloy, indicating its high intrinsic activity against HzOR. The optimal composition of Au1Pt8 electrode demonstrates outstanding characteristics of HER with an ultralow overpotential of 26 mV at 10 mA cm−2 in alkaline medium while requiring 502 mV to attain 10 mA cm−2 for HzOR in 0.5 M N2H4/1.0 M KOH electrolyte. In addition, the assembled overall N2H4 splitting electrolyzer cell using Au1Pt8 alloys as both anode and cathode requires cell voltage of only ~0.172 V at 10 mA cm−2 with tremendous stability over 10 h, which is much lower than the voltage of 1.773 V required for the overall water splitting electrolyzer. The present study validates the feasibility of AuPt alloys for stimulating N2H4 fuel cells in the future to achieve both electrical energy generation and high-rate H2 fuel production.