Optimized the Carrier Transport Path and Separation Efficiency of 2D/2D Heterojunction in Photoelectrochemical Water Splitting

Plasmon-induced hole-depletion layer on p-n heterojunction for highly efficient photoelectrochemical water splitting

The photoelectrocatalytic (PEC) water splitting efficiency of semiconductor photoelectrodes is mainly limited by the effective separation and transfer of photogenerated charges. Zinc indium sulfide-cuprous oxide (ZnIn₂S₄-Cu₂O) p-n heterojunction is constructed to enhance the PEC properties of ZnIn₂S₄. The nickel hydroxide iron oxide (NiFeOOH) layer on the surface of the heterojunction can be used as a hole depletion layer under the induction of plasmon resonance of the most surface silver (Ag) (the holes transferred from Cu₂O valence band to NiFeOOH layer can be excited by Ag to produce hot electron consumption, which makes the last remaining hot holes participate in the water oxidation reaction) to further promote the carrier separation and transfer. The results exhibit that ZnIn₂S₄/Cu₂O/NiFeOOH/Ag photoelectrode with dramatically enhanced photocurrent density of 1.22 mA/cm² at 1.23 V versus the reversible hydrogen electrode (V_RHE), which is 9.4 times higher than the pure ZnIn₂S₄. This work provides a promising concept to design photoelectrodes efficiently in PEC water splitting.

Well-designed oxidized Sb/g-C3N4 2D/2D nanosheets heterojunction with enhanced visible-light photocatalytic disinfection activity

2D/2D heterojunction photocatalysts with excellent photocatalytic activity highlight considerable potential in water disinfection. Here, an oxidized Sb/g-C₃N₄ 2D/2D nanosheets heterojunction (Sb-SbO_x/CNS) was constructed based on a facile one-step liquid-phase exfoliation method using concentrated sulfuric acid. By doing so, bulk Sb and g-C₃N₄ were exfoliated simultaneously and then, intercalated each other. Compared with CNS and Sb-SbO_x, the obtained Sb-SbO_x/CNS demonstrated better photocatalytic disinfection activity towards Escherichia coli K-12 (E. coli K-12) under visible light irradiation. The 5% oxidized Sb/g-C₃N₄ 2D/2D nanosheets heterojunction (5.0% Sb-SbO_x/CNS) exhibited the best photocatalytic performance and admirable cycling stability, which was ascribed to the unique structure where the interfacial charge separation was strengthened by the strong coupling effect between Sb-SbO_x and CNS. Meanwhile, the fundamental mechanism of photocatalytic disinfection was also proposed. The photogenerated ROS (reactive oxygen species) violently attacked the E. coli K-12 membrane, creating massive and irreparable holes on the cell membrane. The leakage of cations (K⁺, Na⁺, Ca²⁺ and Mg²⁺), adenosine triphosphate, total soluble sugar and protein accelerated the destruction of E. coli K-12. Trapping experiments suggested that the photocatalytic disinfection process against E. coli K-12 was dominated by h⁺ generated on 5.0% Sb-SbO_x/CNS. This work offers a new promising way to modify the 2D/2D heterojunction featuring efficient photocatalytic disinfection performance.

Cu-Ion-Implanted and Polymeric Carbon Nitride-Decorated TiO2 Nanotube Array for Unassisted Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting over TiO₂ photoanodes is a promising strategy for hydrogen production due to its eco-friendly, energy-saving, and low-cost nature. However, the intrinsic drawbacks of TiO₂, i.e., the too wide band gap and rapid exciton recombination, significantly limit further enhancement of its performance. Herein, we report a TiO₂ nanotube array (TNA), which is implanted by Cu ions and decorated by polymeric carbon nitride (PCN) nanosheets, as a photoanode for the high-efficiency PEC water splitting. In such designed material, Cu-ion implantation can effectively tailor the electronic structure of TiO₂, thus narrowing the band gap and enhancing the electronic conductivity. Meanwhile, the PCN decoration induces TiO₂/PCN heterojunctions, enhancing the visible light absorption and accelerating the exciton separation. Upon this synergistic effect, the modified TNA photoanode shows significantly improved PEC capability. Its photocurrent density, solar-to-hydrogen efficiency, and applied bias photon-to-current efficiency achieve 1.89 mA cm^-2 at 1.23 V_RHE (V vs reversible hydrogen electrode), 2.31%, and 1.20% at 0.46 V_RHE, respectively. Importantly, this modified TNA supported on a meshlike Ti substrate can be readily integrated with a perovskite solar cell to realize unassisted PEC water splitting.