Enhanced Charge Separation for Efficient Photocatalytic H₂ Production by Long-Lived Trap-State-Induced Interfacial Charge Transfer

Abstract

Photogeneration of charge carriers in semiconductors provides the scientific fundamental for photocatalytic water splitting. However, an ongoing challenge is the development of a new mechanism promoting charge carrier separation. Here we propose a trap-state-induced interfacial charge-transfer transition mechanism (TSICTT), in which electrons in long-lived trap states recombine with holes on the valence band (VB) of the semiconductor, thus prolonging the electron lifetime. We demonstrate this concept in the Sr 4 Al 14 O 25 :Eu 2+ , Dy 3+ /CdS (SAO/CdS) heterostructure, where trapped electrons with a lifetime of up to several hours in the SAO persistent luminescence phosphor (PLP) can continuously consume holes on the VB of CdS nanoparticles (NPs). We discover that the interfacial interaction and the work function difference between SAO and CdS are crucial for the TSICTT, which finally contributes to the improved H 2 production from 34.4 to 1212.9 μmol g CdS −1 h −1 under visible-light irradiation. This model introduces a new strategy to manipulate charge carrier transport for the effective utilization of solar energy.

Achieving Long‐Lived Charge Separated State through Ultrafast Interfacial Hole Transfer in Redox Sites‐Isolated CdS Nanorods for Enhanced Photocatalysis

“…Recently, non‐colloidal CdS NRs heterostructures composing of transition metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS 2 ), [ 9 ] tungsten disulfide (WS 2 ), [ 9a ] and molybdenum diselenide (MoSe 2 ), [ 10 ] as tips have achieved significant photoactivity enhancement in visible light H 2 generation. However, theses TMDs‐tipped CdS NRs systems are prone to reverse electron diffusion back into the CdS NRs, resulting in the recombination with accumulated holes in the CdS NRs mainly due to their slower transfer rate and the sluggish oxidation kinetics of holes compared to active electrons, [ 11 ] This issue has been demonstrated by the positive correlation between the H 2 generation activity and the length of the CdS NRs. [ 9b ] Hence, it is particularly significant to extract hole efficiently in TMDs‐tipped CdS NRs to produce the long‐lived charge separations, which has received less investigation.…”

Interfacial electron modulation of 2D nanopetal ZnIn2S4 with edge-decorated Ni clusters for accelerated photocatalytic H2 evolution

“…The conversion of inexhaustible solar energy into chemical forms, e.g., hydrogen energy, through the assistance of photocatalytic semiconductors will not only satisfy the increasing energy requirements of human society, but will also optimize the world's energy structure with more sustainable and secure options. 1 Since Fujishima and Honda first reported photocatalytic hydrogen production using TiO 2 , 2 many photocatalytic semiconductors have been exploited, such as metal oxides, 3 perovskite, 4 graphitic carbon nitride (g-C 3 N 4 ), 5 metalorganic frameworks (MOF), 6 and covalent organic frameworks (COF). 7 There has been great interest in ZnIn 2 S 4 (ZIS), which is an intriguing member of the AB 2 X 4 family of semiconductors.…”