Multi-component modeling and simulation of a new photoelectrochemical reactor design for clean hydrogen production

Abstract

A novel photoelectrochemical cell design to make a unique reactor is developed and investigated to improve solar to hydrogen conversion efficiency and increase the hydrogen evolution rate. A dome-type photocathode and a circular disc anode are immersed in an alkaline electrolyte of potassium hydroxide in two cylindrical compartments. This new reactor design concerns utilizing the maximum sunlight during the daytime due to the dome shape and increasing the photocathode active area. Four different types of analyses and simulations, including energy, exergy, electrochemical and fluid flow, are performed to investigate the present hydrogen reactor performance using both Engineering Equation Solver and COMSOL software packages. Thermodynamic and electrochemical equations are solved, including mass, energy, entropy, and exergy balance equations, as well as the electrochemical equations. The proposed flow circulation shows a significant effect to avoid the hydrogen bubble coverage phenomenon. The influences of varying the illumined photocathode surface area, the solar irradiance flux, and the quantum efficiency are studied on the hydrogen evolution rate and the solar to hydrogen efficiency. The present hydrogen generation rate and the overall energy system efficiency are 42.1 μg/s, 4.9%, respectively, occurring at solar irradiance of 600 W/m2 and the illumined area of 840 cm2. The highest hydrogen evolution rate is 60.20 μg/s achieved at the illumined photocathode area of 1200 cm2. The maximum reactor energy efficiency found to be 6.52% occurred at a quantum efficiency of 20%, respectively. The study results further confirm that increasing the illuminated photocathode area increases the solar to hydrogen energy efficiency and the hydrogen production rates. Moreover, the hydrogen production rates increase with an increase in the solar irradiance.