Green Hydrogen Production in Photoelectrochemical Artificial-leaf Systems with Different Tandem Solar Cells: An Environmental and Economic Assessment of Industrial-scale Production in China

Different photoelectrochemical (PEC) artificial-leaf systems have been proposed for green hydrogen production. However, their sustainability is not well understood in comparison to conventional hydrogen technologies. To fill this gap, this study estimates cradle-to-grave life cycle environmental impacts and costs of PEC hydrogen production in different provinces in China using diverse tandem solar cells: Ge/GaAs/GaInP (Ge-PEC), GaAs/ GaInAs/GaInP (GaAs-PEC) and perovskite/silicon (P-PEC). These systems are benchmarked against conventional hydrogen production technologies − coal gasification (CG) and steam methane reforming (SMR) − across 18 environmental categories, life cycle costs and levelised cost of hydrogen (LCOH). P-PEC emerges as the best options, with 36–95 % lower impacts than Ge-PEC and GaAs-PEC across the categories, including the climate change impact (0.38–0.52 t CO2 eq./t H2) which is 77–79 % lower. Economically, P-PEC shows 81–84 % lower LCOH (2.51–3.81 k$/t). Compared to SMR and CG, P-PEC reduces the impacts by 23–98 %, saving 3.67–38.5 Mt of CO2 eq./yr. While its LCOH is 5 % higher than that of conventional hydrogen, it could be economically competitive with both SMR and CG at 10 % higher solar-to-hydrogen efficiency and 25 % lower operating costs. In contrast, Ge-PEC and GaAs-PEC, while achieving much lower (81–91 %) climate change and some other impacts than the conventional technologies, face significant economic challenges. Their LCOH (21.51–32.82 k$/t for Ge-PEC and 16.96–25.89 k$/t for GaAs-PEC) is 7–9 times higher than that of the conventional hydrogen due to the high solar cell costs. Therefore, despite their environmental benefits, these technologies require substantial cost reductions to become economically viable.