• Matveev, Vadim

Abstract

<jats:p>Today, hydrogen is recognized as a promising fuel, which is characterized by high heat generation and combustion temperature. It is also characterized by environmental safety due to the fact that no greenhouse gases are formed during the combustion of hydrogen. There are various methods of hydrogen production: traditional methods, which include electrolysis of water and conversion of hydrocarbons, and thermochemical ones. A cheap method of hydrogen obtaining from natural gas and coke is accompanied by the carbon oxides formationю Thermochemical methods are require high temperatures (up to 1000°C). The method for hydrogen production by electrolysis of aqueous solutions of alkali metal hydroxides is the most energy-intensive. However, it is considered one of the most promising in the European Union. To reduce energy consumption for hydrogen production, the authors suggest replacingthe positive electrode, which normally produces oxygen, with a dissolving anode with an equilibrium potential lower than that of oxygen, such as an iron electrode. In this case, with such a combined electrochemical method, the decomposition voltage in the system will be 0.44 V against 1.23 V with traditional water electrolysis. The overvoltage of iron dissolution in a chloride medium is several tens of millivolts. However, the potential difference between the anode and cathode ΔU becomes smaller than the equilibrium potential difference ΔE0 = 0.44 V. This research aims to substantiate the choice of the composition and concentration of electrolytes: catholyte –to ensure conditions for reducing energy consumption for hydrogen release; anolyte – to prevent passivation of the iron anode, which can lead to the oxygen release. This work results in research of the cathodic process of hydrogen release in the following solutions: 1 M (= mol/L) NaCl with the addition of 1 M hydrochloric acid in the amount of 5, 10, 15, 20 mL. Platinum is used as a cathode for the electrolysis process. The anode material is an iron, St3 grade. It has been found that in the range of changes in the composition of the electrolyte from neutral (1 M NaCl) to acidic (1 M HCl), a change in the mechanism of water discharge is observed. In a neutral medium, the discharging occurs according to the Heyrovsky mechanism, and in an acidic medium - according to the Volmer mechanism. The choice of the anolyte composition and concentration is complicated by the need to provide an acidic medium containing chlorine ions to prevent passivation of the anode. The acidity of the solution must be at least 3 for the successful extraction of dissolution products of the iron anode.</jats:p>

Topics

• impedance spectroscopy
• Carbon
• Oxygen
• extraction
• Platinum
• Hydrogen
• combustion
• iron
• decomposition
• Alkali metal
• dissolving