Sonoelectrochemical production of hydrogen via alkalinewater electrolysis

Alkaline water electrolysis is a promising technology to produce clean and pure hydrogen. This technology coupled with the ultrasound results in an enhanced rate of hydrogen production. The recent technologies in the area of electrolysis are the application of solar energy using photovoltaic cells to supply electricity, steam electrolysis, PEM electrolysis, the application of magnetic field and high temperature solid oxide electrolysis cell. The literature studies indicate an improved mass transfer and 10%-25% energy saving using the ultrasound. This work continues the previous research done in this area by investigating the effect of the ultrasound on a conventional water electrolysis cell along with other parameters subject of alteration such as electrode active surface area, concentration and temperature. The hydrogen production was measured using a digital hydrogen flowmeter; the average production efficiency and energy efficiency of the electrolysis cell were 72% and 14.5% respectively. It was calculated that the ultrasound increased the production efficiency by 6% and energy efficiency by 1.3%. The act of the ultrasound resulted in bubble removal from the surface of the electrode and the solution therefore prepared the electrode surface for the electrochemical reactions thus enhanced the hydrogen generation. The current generation was enhanced by about 70% when the electrode active surface area was increased by about 45%, the hydrogen production rate however was not improved in an orderly fashion as a result of this increase in the electrode surface area. This increase is resulted from a larger electrode surface area available for the reaction, which refers to more active sites. The lowest ohmic resistance in our cell was obtained at 15M experiment, which was about 1.5 \(\Omega\) at 3.3V applied potential. This was slightly higher than 0.8 \(\Omega\) mentioned for a very recent work carried out in an advanced alkaline electrolysis cell, which benefited from a hydrophilic separator between the electrodes using a 28% KOH electrolyte solution. The average low ohmic resistance in our study for low concentration experiments (0.1M) was about 14\(\Omega\) at 30V.