Glycerol (photo)electro-oxidation on carbon supported Ag nanoparticles modified with low amounts of Pt. Activity, selectivity and the effect of visible-light irradiation

Abstract

The electrochemical production of hydrogen arises as one of the most important strategies to mitigate the problems caused by the pollution and the strong dependence on fossil fuel-derived sources of energy. Thus, improvements in the overall electrolysis process can contribute with this task. One of the problems that has been confronted for decades is the sluggishness of the electro-oxidation of water by preparing a myriad of materials with limited success. Therefore, instead of keeping on looking for materials to be applied for this reaction, one possibility is to change the water for another cheap substance, easier to be oxidized. In this context, biomass-derived resources, like several alcohols and polyols, emerge as suitable candidates to be oxidized in the anodes of electrolyzers. This way, it is possible to concomitantly obtain high purity hydrogen at the cathode and value-added biomass derivatives at the anode. Herein, to avoid/decrease the use of noble metals, we prepare Ag/C catalyst and modify the Ag surface by different quantities of Pt. The catalyst containing only 0.5% of Pt reached half the electro-oxidation peak current of Pt/C. Besides, considering the current normalized by Pt mass, this material is around 80 times more active than Pt/C. Apart from the electrochemical results, we irradiated our materials with white light and observed an increased activity for the electro-oxidation of glycerol, showing the presence of a plasmonic effect. FTIR in situ and HPLC online showed that all the catalysts produced glycerate, lactate, glycolate and formate and that the selectivity do not change with the irradiation of light. The most important difference between the materials was that while Pt/C produce carbonate, this specie was not detected for Pt-Ag/C. Finally, the materials were also tested for the electro-oxidation of ethanol, showing that they are promising for the electro-oxidation of several alcohols/polyols. Therefore, this study paves the way for future optimization of Ag/C catalyst modified on its surface with different more active materials that must be afterward tested in real devices like, for instance, anion exchange membrane electrolyzers.

Photoelectrochemical Glycerol Oxidation Coupled with Hydrogen Production

“…Furthermore, glyceric acid and lactic acid have been identified as the primary C 3 products in certain studies. [55][56][57] However, the design strategy of photoanodes for enhancing selectivity still requires further exploration. [26] Copyright 2019 Springer Nature.…”

First Pem Photoelectrolyser for the Simultaneous Selective Glycerol Valorization into Value-Added Chemicals and Hydrogen Generation

“…the reaction has not always resulted in the production of the desired primary products. For example, in some cases, the selectively obtained product is glycerate [18][19][20], glycolate [20,21], lactate [20] or formate [22][23][24][25].…”

“…The utilization of precious metals like Pt [20,[26][27][28][29], Au [30][31][32] and Pd [33][34][35], either as main active phase or as co-catalyst, decreases the PC and PEC economic competitiveness. In particular, in this work, the concern of replacing the noble metals has been focused on the anodic catalyst.…”

“…iii) Most of the studies are carried out under harsh reaction conditions, i.e., using acid (e.g., H 2 SO 4 ) [24,[36][37][38] or alkaline concentrated solutions (e.g., KOH, NaOH) [18][19][20][21][22] as electrolytes, increasing the safety risks of storage and transportation and environmental hazards in large-scale production. For instance, Wang et al proposed a CoNiFe-LDHsdecorated Ta 3 N 5 nanotube array for the simultaneous generation of anodic formate and cathodic hydrogen in a 1.0 M NaOH electrolyte, [22] while the highest DHA selectivities (above 50%) have been reached by using solutions with pH = 2 [24,[36][37][38].…”