Lawrence Berkeley National Laboratory

Photoelectrochemical (PEC) water splitting provides a pathway to generate sustainable clean fuels using the two most abundant resources on Earth: sunlight and water. Currently, most of the successful models of PEC cells are still fabricated on small scales near 1 cm , which largely limits the mass deployment of solar-fuel production. Here, the scale-up to 8 cm of an integrated PEC (IPEC) device is demonstrated and its performance compared to a 1 cm IPEC cell, using state-of-the-art iridium and platinum catalysts with III–V photoabsorbers. The initial photocurrents at 1 sun are 8 and 7 mA cm with degradation rates of 0.60 and 0.47 mA cm  day , during unbiased operation for the 1 and 8 cm devices, respectively. Evaluating under outdoor and indoor conditions at two U.S. National Laboratories reveals similar results, evidencing the reproducibility of this design's performance. Furthermore, the emerging degradation mechanisms during scale-up are investigated and the knowledge gained from this work will provide feedback to the broader community, since PEC device durability is a limiting factor in its potential future deployment. 2 2 2 −2 −2 −1 2