Optimized photoelectrochemical tandem cell for solar water splitting

In the field of photoelectrochemical (PEC) hydrogen production most studies focus on developing efficient nanostructured materials and less attention is given to the optimization of PEC devices. However, the reactor design greatly influences the overall performance of these devices and it is a key element to turn PEC hydrogen generation competitive and marketable. In this work, a 50 cm2 tandem PEC-PV cell, named CoolPEC cell (compact, optimized, open light PEC cell), was designed and optimized for continuous operation comprising improved key features: i) an open path for the sunlight to reach a PV cell placed at the back of the PEC cell; ii) a photoelectrode that simultaneously is one of the windows of the cell; iii) an integrated manifold to feed the electrolyte. CFD simulations were performed to improve the reactor design assuring good heat dissipation and an efficient collection of evolved oxygen and hydrogen in separated compartments. The CoolPEC cell presented a stable performance over 42 days (1008 h) in a continuous operation mode. The 50 cm2 hematite photoelectrode produced ca. 0.45 mA cm−2 at a bias potential of 1.6 V provided by two silicon heterojunction (SHJ) solar cells, under 1000 W m−2 and with constant electrolyte feeding at 45 °C. SEM, EDS and ICP analyses confirmed that the hematite photoelectrode was resistant to the accelerated corrosion promoted by the operating conditions.