Interfacial Engineering for the Fast Carrier Tunneling Channel by a Novelty Quaternary Layered Photoanode

Developing an advanced photoanode structure to decrease the charge recombination is a mandatory requirement to enhance charge separation and transfer for photoelectrochemical reactions. Herein, we report an interfacial engineering design of quaternary layered Bi2S3/Bi2Mo2O9/Bi2S3/Bi2Mo2O9 by using a successive ionic layer absorption and reaction method. The synergistic effect of double p–n junctions combined with the Z-scheme system by band structure matching is the key point for this novelty design. The double p–n junctions can reinforce the charge separation when the semiconductor absorbs photons. The third ultrathin interlayer Bi2Mo2O9 sandwiched between two Bi2S3 layers plays a role as a carriers’ tunneling channel thanks to the Z-scheme system, which can accelerate the directional flowing of the electron and hole in the bilayer Bi2S3. Such a quaternary layered structure will be a “highway” for the electron transfer to the bulk, and the transfer of holes is to the surface where water oxidation takes place. This optimized structure exhibits a remarkable charge separation efficiency of 41% and outstanding photocurrent density of 3.1 mA cm–2 at 1.23 V vs RHE for water oxidation. Dynamic analysis displays that the charge transport time across the multilayer structure (5 μs) is much lower than that of the single-layer photoanode (58 μs), implying fast oxidation kinetics under a sunlight-driven water-splitting system.