Solar water splitting under natural concentrated sunlight using a 200 cm2 photoelectrochemical-photovoltaic device

Abstract This work reports a 200 cm2 PEC-PV device that comprises four 50 cm2 PEC cells coupled in a modular array and optimized for continuous operation under concentrated sunlight. The developed module is the second largest PEC-PV device ever reported and the first tested under natural concentrated sunlight (up to 12.8 kW m−2). Demonstration tests were conducted outdoor in a continuous operation mode, over four days and using highly stable hematite photoelectrodes. When assembled with four multi-PE windows, each comprising eight small nanostructured photoelectrodes connected in parallel, the module generated a stable current density of ca. 2.0 mA cm−2 at 1.45 V, resulting in an average hydrogen production rate of 5.6 × 10−5 gH2 h−1 cm−2 (based on the net active area). A maximum current density of ca. 4.0 mA cm−2 was reached during J-V measurements (before the dark current onset potential). It was observed that when hematite photoelectrodes are subjected to gradually higher solar irradiances the generated photocurrent follows a logarithmic saturation behaviour. This work provides important insights for demonstrating the viability of solar-driven water electrolysis by presenting a PEC-PV device that answers to the main challenges of large-scale photoelectrochemical hydrogen production.