Atomic Insights for Optimum and Excess Doping in Photocatalysis: A Case Study of Few‐Layer Cu‐ZnIn₂S₄

Abstract

Herein, an example of Cu-doped few-layer ZnIn 2 S 4 nanosheets is used to reveal the origin of optimum and excess doping for photocatalysts at atomic level. Results show that the metal-S 4 coordination maintains well with 0.5 wt% Cu substituted Zn atoms in the lattice. The introduced Cu atoms bring electronic acceptor states close to the valence band (VB) maximum and thus ensures higher charge density and efficient carrier transport, resulting in an optimum hydrogen evolution rate of 26.2 mmol h −1 g −1 and an apparent quantum efficiency of 4.76% at 420 nm. However, a distorted atomic structure and largely upshift of VB maximum with Cu-S 3.6 coordination are found with excess doping concentration (3.6 wt%). These bring the heavy charge recombination and consequentially dramatic reduced activity. This work provides a new insight into elemental doping study and takes an important step toward the development of ultrathin 2D photocatalysts.

Unraveling the Interfacial Charge Migration Pathway at the Atomic Level in a Highly Efficient Z‐Scheme Photocatalyst

“…To clarify the role of Co 5.8 –S transition layer, we employed steady‐state surface photovoltage spectroscopy (SS‐SPS), transient‐state surface photovoltage spectroscopy (TS‐SPS), electrochemical impedance spectroscopy (EIS), and transient absorption spectroscopy (TAS). The SS‐SPS spectra (Figure a) display a clear surface photovoltage response in the range (300–550 nm) for CdS and no response for CoS 2 , thus indicating no efficient separation of photogenerated charges in its band . The intensity of SS‐SPV for CdCoS has been enhanced, which clearly reveals that the signal of CdCoS is not simply a superposition of the signals of CdS and CoS 2 .…”

Single crystalline quaternary sulfide nanobelts for efficient solar-to-hydrogen conversion

“…33 ). The current densities are higher than the recently reported copper-based quaternary sulfides due to the 2D structure and exposed facet in promoting the transportation and separation of photogenerated electrons and holes 14 , 51 – 53 .…”

“…Copper-based quaternary sulfide nanomaterials, especially for Cu-Zn-In-S (CZIS) and Cu-Zn-Ga-S (CZGS), which consist of non-toxic and earth abundant elements are attractive candidate for solar-to-hydrogen conversion because of their tunable bandgap, environmental benignity, good thermal and chemical stability, and easy synthesis from abundant and inexpensive precursors [10][11][12][13][14][15][16] . Since Domen and co-workers reported CZIS enabled photocatalytic hydrogen production aided by co-catalyst, many efforts have been paid on developing copper-based multinary sulfide photocatalysts, which hold great potentials in solar energy conversion and chemical synthesis [17][18][19][20][21] .…”

A Review and Recent Developments in Full‐Spectrum Photocatalysis using ZnIn2S4‐Based Photocatalysts

“…Another research by Wang et al has reported that the incorporation of Cu atoms can make the electron acceptor state closest to the VB, thereby ensuring a higher charge density and effective carrier transport, so that the optimal hydrogen evolution rate can reach 26.2 mmol h −1 g −1 and the AQE is as high as 4.76% at 420 nm. [ 127 ] They found that the optimal amount of Cu doping is 0.5 wt%, and excessive doping of 3.6 wt% is harmful to the activity. They further clarified the optimal doping and excessive doping mechanism of Cu‐doped ZIS.…”