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In this paper, the results of an experimental study on hydrogen production at a tungsten discharge electrode with negative polarity in the DC electrolysis of a typical 10 wt% Na₂CO₃ aqueous solution in three operational regimes (the Faradaic, transition, and plasma-driven solution electrolysis (PDSE)) are presented for the first time. To focus the study on hydrogen production, a flowing inert gas (argon) was used to transport the gas mixture produced at the discharge electrode and prevent any other potential chemical reactions. The results showed that the highest hydrogen production rate of 0.147 g(H₂)/h was achieved in the cathodic PDSE regime at the applied DC voltage of 198 V. However, the energy yield of hydrogen production of 0.405 g(H₂)/kWh obtained at the applied voltage range of 141–170 V in the PDSE regime was lower than that obtained in the Faradaic regime (0.867 g(H₂)/kWh) at 28 V. The energy balance of hydrogen production in the cathodic PDSE regime for the typical aqueous solution of Na₂CO₃ carried out for the first time showed that a significant share (˃98%) of the electrical energy consumed is spent on heating and evaporation of the electrolytic solution. This explains why the energy yield of hydrogen production is low in the PDSE regime. Because most of the energy is consumed for heat generation in the cathodic PDSE regime, organic liquid hydrogen carriers, such as alcohols, which have a lower boiling temperature, heat of evaporation, and standard Gibbs free energy, should be considered better aqueous electrolytic solutions in terms of the energy yield of hydrogen production in the PDSE regime. Full article

This paper reviews the progress in applying the plasma-driven solution electrolysis (PDSE), which is also referred to as the contact glow-discharge electrolysis (CGDE) or plasma electrolysis, for hydrogen production. The physicochemical processes responsible for the formation of PDSE and effects occurring at the discharge electrode in the cathodic and anodic regimes of the PDSE operation are described. The influence of the PDSE process parameters, especially the discharge polarity, magnitude of the applied voltage, type and concentration of the typical electrolytic solutions (K₂CO₃, Na₂CO₃, KOH, NaOH, H₂SO₄), presence of organic additives (CH₃OH, C₂H₅OH, CH₃COOH), temperature of the electrolytic solution, the active length and immersion depth of the discharge electrode into the electrolytic solution, on the energy efficiency (%), energy yield (g(H₂)/kWh), and hydrogen production rate (g(H₂)/h) is presented and discussed. This analysis showed that in the cathodic regime of PDSE, the hydrogen production rate is 33.3 times higher than that in the anodic regime of PDSE, whereas the Faradaic and energy efficiencies are 11 and 12.5 times greater, respectively, than that in the anodic one. It also revealed the energy yield of hydrogen production in the cathodic regime of PDSE in the methanol–water mixture, as the electrolytic solution is 3.9 times greater compared to that of the alkaline electrolysis, 4.1 times greater compared to the polymer electrolyte membrane electrolysis, 2.8 times greater compared to the solid oxide electrolysis, 1.75 times greater than that obtained in the microwave (2.45 GHz) plasma, and 5.8% greater compared to natural gas steam reforming. Full article