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

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.