Electrochemical valorization of crude glycerol in alkaline medium for energy conversion using Pd, Au and PdAu nanomaterials

• Published in: Fuel (Guildford) Vol. 262; p. 116556
• Main Authors: Velázquez-Hernández, Isaac, Zamudio, Evelyn, Rodríguez-Valadez, Francisco J., García-Gómez, Nora A., Álvarez-Contreras, Lorena, Guerra-Balcázar, Minerva, Arjona, Noé
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.02.2020; Elsevier BV
• Subjects: Bimetals; Biodiesel fuels; Biofuels; Crude glycerol; Current density; Diesel; Electrocatalysis; Electrochemistry; Electron micrographs; Energy conversion; Glycerol; Glycerol oxidation; Gold; Ionic liquids; Methanol; Nanomaterials; Nanoparticles; Nanotechnology; Oxidation; Palladium; PdAu nanoparticles; Purification; Sonication; Transesterification; Ionic liquids; Electrocatalysis; Crude glycerol; Glycerol oxidation; PdAu nanoparticles
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2019.116556

Pd/C, Au/C and PdAu with different compositions (1:1, 3:1, and 5:1 Pd: Au) were synthesized by a green method and used as electrocatalysts for crude glycerol electro–oxidation. Pd5Au1/C presented the highest current density (140.1 mA mgPdAu−1). In addition, this material displayed higher current density for crude glycerol than for analytical grade glycerol electro–oxidation due to its capability to oxidize also the residual methanol presented in crude glycerol. [Display omitted] Crude glycerol is a byproduct from biodiesel production, and due to overproduction, new applications requiring the minimum purification steps are needed. The electrochemical valorization of crude glycerol is one of the most attractive applications. In this work, the use of crude glycerol as fuel for energy conversion applications was studied on noble materials such as Pd/C, Au/C and PdAu/C nanoparticles with different Pd/Au atomic composition (1:1, 3:1 and 5:1) with the aim of identifying the main barriers to improve the crude glycerol electro–oxidation reaction (crude GOR). High–resolution transmission electron micrographs revealed that Pd and PdAu nanoparticles had average sizes below 10 nm, while Au nanoparticles had particle sizes of 16.2 ± 1.4 nm. Besides, crude glycerol was obtained from a biodiesel prepared by a transesterification reaction assisted by sonication, resulting in a crude glycerol with a high glycerol content (>95 V/V %). The electrocatalytic evaluation indicated that Pd5Au1/C was the material with the highest current density for crude GOR, displaying 140.1 mA mgPdAu−1, which was 1.8, 2.73, 2.79, 4.14 and 2.2 times higher to that obtained for Pd3Au1/C, Pd/C, Au/C, Pd1Au1/C, and commercial Pd/C, respectively. Moreover, this current density was 20% higher to that obtained for analytical grade glycerol, which was attributed to the bimetallic capability of Pd5Au1 to oxidize both, glycerol and methanol presented in crude glycerol. In summary, it was found that the competition between the adsorption of methanol and glycerol on active sites plays a major role on the activity for crude GOR.