All-perovskite-based unassisted photoelectrochemical water splitting system for efficient, stable and scalable solar hydrogen production

For practical photoelectrochemical water splitting to become a reality, highly efficient, stable and scalable photoelectrodes are essential. However, meeting these requirements simultaneously is a difficult task, as improvements in one area can often lead to deteriotation in others. Here, addressing this challenge, we report a formamidinium lead triiodide (FAPbI₃) perovskite-based photoanode that is encapsulated by an Ni foil/NiFeOOH electrocatalyst, which demonstrates promising efficiency, stability and scalability. This metal-encapsulated FAPbI₃ photoanode records a photocurrent density of 22.8 mA cm⁻² at 1.23 V_RHE (where V_RHE is voltage with respect to the reversible hydrogen electrode) and shows excellent stability for 3 days under simulated 1-sun illumination. We also construct an all-perovskite-based unassisted photoelectrochemical water splitting system by connecting the photoanode with a same-size FAPbI₃ solar cell in parallel, which records a solar-to-hydrogen efficiency of 9.8%. Finally, we demonstrate the scale-up of these Ni-encapsulated FAPbI₃ photoanodes into mini-modules up to 123 cm² in size, recording a solar-to-hydrogen efficiency of 8.5%.