One stone, two birds: Multifunctional hierarchical iron sulfide nanosheet arrays enabling self-powered solar thermoelectric water electrolysis

Solar water splitting is essential for future sustainable hydrogen production using renewable resources, but it remains challenging due to expensive solar generators and inefficient electrocatalysts. Herein, we propose a solar thermoelectric water electrolysis system using multifunctional iron foam-supported iron sulfide nanosheet arrays (FeS/IF) as the photothermal conversion unit in solar thermoelectric generator (STEG) and electroactive electrode in water electrolysis. The photothermal FeS/IF rapidly converts solar light to localized heat, supplying the desirable temperature difference for thermoelectric power generation. Meanwhile, the FeS/IF acts as a bifunctional electrode to effectively catalyze the hydrogen and oxygen evolution reactions in alkaline media. As a prototype integrated system, four series-connected FeS/IF-STEG are applied to self-power water splitting with the production rate of 10.7 and 5.3 μmol h−1 for hydrogen and oxygen, respectively. The present study offers new opportunities for rational design of integrated energy systems from renewable solar to sustainable hydrogen.