Investigation of a solar hydrogen generating system design for green applications

Highlights: • The current study depicts a novel photoelectrode for hydrogen production. • Energy and exergy modeling of the photoelectrochemical cell is conducted. • Electrochemical modeling of the photoelectrochemical cell is calculated. • Multiphase flow is simulated to detect the fluid characteristics by COMSOL. • This system attains 6.69% highest efficiency and H₂ generation rate of 55.20 μg/s. This study presents a unique dome photoanode design that can harvest the maximum delivered sun rays over the daytime due to its specific dome design to enhance the solar to hydrogen energy efficiency and improve the hydrogen mass generation rate. The photoanode and cathode domes are placed in a potassium hydroxide electrolyte inside two cylindrical vessels. The coupled electrochemical, exergy, energy, as well as fluid flow analyses, are conducted to examine the proposed photoelectrochemical cell designs using both COMSOL and Engineering Equation Solver software packages. The electrochemical process equations are simulated extensively to investigate the impacts of changing the illuminated electrode surface area, quantum efficiency, solar radiation intensity, and photocurrent density upon the corresponding energy efficiency as well as hydrogen generation rate. The thermodynamic balance equations are also developed to predict the exergy and energy for all inputs and outputs. The impact of electrolyte flow circulation on the oxygen bubble formation is formulated in a way to prevent the bubble coverage phenomenon. The numerical results showed that the hydrogen mass generation rate and solar to hydrogen efficiency are 26.16 μg/s and 4.38%, respectively, which happens at 600 W/m² of solar irradiance, 10% quantum efficiency, and 569 cm² illuminated electrode surface area. The maximum mass-based hydrogen generation rate and the overall energy efficiency, which are found to be 55.20 μg/s and 6.69%, are achieved at a 800 cm² illuminated photoanode surface area, a 600 W/m² solar radiation intensity, a 3.3 mA/cm² current density, and a 10% quantum efficiency.