In today's world we are intensively confronted with challenges related to our dependence on fossil fuels whose negative environmental impacts are accelerating the climate stability of this planet. The gradual increase in industrialisation, urbanisation and the consequent population growth are placing increasing demands on finite fossil fuel and energy supplies which has led to today's development, increasingly focusing on the search for alternative energy sources. Decarbonisation has thus become the main strategy to limit the use of fossil fuels and minimise greenhouse gas emissions. The transition to a more sustainable and low-carbon energy system is advocated by the hydrogen economy which focuses on the development of technologies to produce clean or green hydrogen from renewable energy sources, the construction of infrastructure for its storage and the distribution and implementation of hydrogen in various sectors, including transport, industry and electricity generation. The thesis focuses on the production of green hydrogen by electrolysis of water and electrolysis of HCl (hydrochloric acid) using a PEM electrolyser.
The main purpose of the experimental work is to compare the efficiency, more specifically the amount of hydrogen (H2) produced in water electrolysis with HCl electrolysis, if the latter offers a higher productivity in hydrogen production, with the additional advantage of generating a secondary marketable product (Cl$_2$). The implementation of HCl electrolysis on a larger scale is also conditional on better results compared with water electrolysis, which could be added to many plants whose by-product is precisely HCl in large quantities, with which the market is already somewhat oversupplied.
During the experiments, I also monitored the parameters of HCl electrolysis (temperature, electrolyte concentration, electrical voltage), which I varied during the experiments and studied on the basis of the results obtained. In the presence of a higher electrical potential of the system, more hydrogen was consequently produced, as the rate of the reduction reaction at the cathode is proportional to the applied potential. Higher temperature conditions increase the kinetic energy of the molecules which, due to the higher number of successful collisions, accelerates the reduction reaction to produce hydrogen. As a consequence, the higher kinetic energy at higher temperature makes the materials and the electrolyte more conductive, which also lowers the overvoltage potential.
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