Two‐Stage Solar Hydrogen Production in a Tandem Photothermal Catalytic‐Electrocatalytic System

ABSTRACT Solar‐driven water splitting is an effective method for hydrogen production. However, thermal energy generated during photochemical conversion was often overlooked and wasted, restricting the conversion efficiency of solar to hydrogen (STH). Here, a novel tandem photothermal catalytic‐electrocatalytic system was proposed and designed for cascade hydrogen production from full‐spectrum solar energy via a two‐stage technology pathway. The hybrid device (PTC/TEG‐EC) integrated a photothermal catalytic (PTC) reactor, a thermoelectric generator (TEG) module, and an electrochemical (EC) cell, where high‐energy photons and other photons can be collaboratively converted into hydrogen energy through a direct PTC route in the PTC unit and an indirect thermoelectric‐driven water electrolysis route in the TEG‐EC unit, respectively. Under light irradiation, the operation current density of the TEG‐EC unit can be obtained as 24.46 mA·cm −2 , providing an additional contribution to STH beyond the PTC reaction. The overall STH efficiency of PTC/TEG‐EC reached 0.186%, achieving a 5.58‐fold improvement over the traditional PTC reactor. Theoretically, the two‐stage pathway is expected to break through the thermodynamic limiting efficiency of single‐pathway photochemical reaction, mainly attributed to the achievement of low‐grade waste heat to hydrogen, which is complementary to PTC conversion. Therefore, the novel system offered a promising and effective technological route for obtaining hydrogen from full‐spectrum solar energy.