(688f) Reactor Design Considerations for the Efficient Hydrogen Production through Combined Natural and Artificial Light-Driven Photocatalytic Water Splitting

Hydrogen production via photocatalytic water-splitting enables a pathway towards its sustainable production, although it suffers from low efficiencies and the intermittent character of solar power, especially compared to traditional methods such as steam reforming of methane into hydrogen, and the industrially mature water electrolysis. A novel process is introduced in this work, which combines natural and artificial light to power a photocatalytic water-splitting process that can continuously run day and night. In addition, the process uses non-potable water sources to be split, based on an inhouse developed low cost organic catalyst, to achieve further environmental savings.

In this study, the investigation on the coupling of the artificial (LED) and natural light sources is presented. A lab-scale photoreactor was built, with a solar simulator used as a natural sunlight source. For artificial light, several wavelengths of 10-20 strings of 3W LEDs, ranging from 365-430nm were tested, in various distributions and power levels, with the goal of optimizing hydrogen production. Distribution and placement of the LEDs was studied to provide uniform flux distribution along the reactor vessel surface. The optimal thickness of the reaction catalyst/water mix, in relation to the UV light penetration, was also quantified and modeled.

Preliminary test results indicate that UV light at 380nm was optimal for hydrogen production for the Carbon Organic Framework (COF) photocatalyst used. In addition, by examining the efficiency of converting natural sunlight to electricity via photovoltaic panels, and then into artificial light via LEDs, powering the water-splitting process solely via UV-LEDs was found to be viable from a green, emission free electricity perspective, as hydrogen production via LEDs outperformed natural sunlight by up to 10x more. Nevertheless, solar driven photocatalysis still possessed an advantage of passively heating the reaction mixture, since higher than ambient temperatures were found to be positively correlated with hydrogen production.