Poznan University of Technology, Institute of Chemistry and Technical Electrochemistry
Berdychowo 4, 61-131 Poznan, POLAND
adam.slesinski@put.poznan.pl
Water electrolysis has recently become an interesting route to produce valuable chemicals such as hydrogen and hydrogen peroxide. It is readily possible to obtain both products at separate electrodes during water reduction and oxidation, respectively. This not only eliminates the necessity for further separation, but also accounts for cell current efficiency. One of the most important aspects in the design of electrolysis cells are the materials of electrodes, as they mostly govern the overpotentials encountered during the electrochemical reactions.
Noble metals are known to serve perfectly as hydrogen evolution catalysts, almost totally reducing the overpotential. However, due to their scarce availability, they are incorporated within carbon composites with loadings tending to be reduced to values as low as 0.05 mg cm-2.
On the other hand, noble metals in positive electrode facilitate the 4e– water oxidation to produce gaseous oxygen, rather than hydrogen peroxide via 2e– pathway. Therefore, there is a need to search for catalyst with selectivity towards the latter reaction.
The literature points to the use of catalysts mainly based on metal oxides and metal sulphides. While these substances properly catalyse the reaction of interest, the efficient production of H2O2 can also be triggered using modified activated carbon materials, which production can be more scalable and thus cheaper.
The adjustment of activated carbon surface chemistry in this work is done using widely available oxidants: nitric acid, ammonium persulphate and hydrogen peroxide. The rates of hydrogen and oxygen (as by-product) evolution are monitored with pressure transducer coupled with syringe pump for progressive gas accumulation. This, together with quantitative chemical analysis of hydrogen peroxide produced give full insight into the ongoing processes. It turned out during investigation that the gases are being produced even when no associated current leap is observed in cyclic voltammetry experiment. It provides an important observation to be considered during carrying out the electrolysis process.
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Figure 1. Cyclic voltammetry of the system based on Kuraray YP-50F in 1 mol L-1 NaHCO3 electrolyte. A) cyclic voltammogram, B) CV in the time domain showing pressure variation due to gases production. This project has received funding from the European Innovation Council (EIC) under grant agreement No 101069981. The EIC receives support from the European Union’s Horizon Europe Research and Innovation Programme. |
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