On the promotional effect of Cu on Pt for hydrazine electrooxidation in alkaline medium

• Published in: Applied catalysis. B, Environmental Environmental, 2018-11, Vol.236, p.36-44
• Main Authors: Crisafulli, Rudy, de Barros, Vanine V. Silva, Rodrigues de Oliveira, Francisca E., de Araújo Rocha, Thairo, Zignani, Sabrina, Spadaro, Lorenzo, Palella, Alessandra, Dias, José A., Linares, José J.
• Format: Article
• Language: English
• Subjects: Alkaline media; Alkalinity; Black carbon; Carbon black; Catalytic oxidation; Copper; Copper oxides; Direct hydrazine fuel cells; Electrocatalysis; Electrocatalysts; Electrochemistry; Energy transmission; Fuel cells; Fuel technology; Hydrazine; Hydrazines; Image transmission; Intermetallic compounds; Optimization; Photoelectron spectroscopy; Platinum; Platinum base alloys; PtCu/C; Reducing agents; Transmission electron microscopy; Voltammetry; X ray analysis; X ray photoelectron spectroscopy; X-ray diffraction
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2018.05.016

[Display omitted] •Cu promotes hydrazine electroxidation on Pt in an alkaline environment.•PtCu alloy exerts a promotional effect on the Pt electronic environment.•The presence of copper oxides also assists in the hydrazine electroxidation.•The equiatomic Pt:Cu ratio is the most electrochemically active one.•A 78.1% increase in the maximum power density compared to Pt/C was achieved. Pt/C and PtCu/C electrocatalysts with nominal Pt:Cu atomic ratios of 75:25, 50:50, and 25:75 were prepared using N2H4 as reducing agent and carbon black Vulcan XC-72R as support. The obtained materials were physically characterized by X-ray diffraction, Energy-Dispersive X-ray analysis, Transmission Electron Microscopy images, X-ray Photoelectron Spectroscopy (XPS), and Temperature-Programmed Reduction analysis. Cyclic voltammetry, linear sweep voltammetry, and chronoamperometry (TPR) measurements were carried out in a three-electrode glass cell to evaluate the electrochemical activity towards hydrazine electrooxidation in alkaline medium along with single-cell direct hydrazine fuel cell (DHFC) tests. The actual composition of the electrocatalysts evidenced a slightly lower Cu fraction compared to the nominal one. The X-ray diffractograms of the electrocatalysts showed the typical face-centered cubic structure of Pt alloys, with the highest fraction of Cu alloyed to Pt being achieved with the almost equiatomic catalyst. An important fraction of the remaining non-alloyed Cu is in the form of a copper oxide, as evidenced by XPS and TPR measurements. The electrochemical tests evidenced that the coexistence of part of the Cu alloyed with Pt and copper oxide achieved in the PtCu/C electrocatalysts enhances the performance compared to Pt/C. In particular, the optimum formulation is attained by the Pt53Cu47/C electrocatalyst, allowing maximization of the electrocatalytic activity towards hydrazine electrooxidation and the single-cell performance at 60 and 80 °C.