期刊
ACS APPLIED MATERIALS & INTERFACES
卷 12, 期 39, 页码 43728-43740出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.0c12583
关键词
hydrogen evolution; quantum dots; 2D nanosheets; 2D/0D heterostructures; photocatalytic water splitting; hard X-ray photoemission spectroscopy; transient absorption spectroscopy
资金
- National Science Foundation under DMREF [1627197, 1626967, 1627583]
- DOE Office of Science by Argonne National Laboratory [DE-AC02-06CH11357]
- U.S. DOE Office of Science Facility, at Brookhaven National Laboratory [DE-SC0012704]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1627583, 1626967] Funding Source: National Science Foundation
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1627197] Funding Source: National Science Foundation
Solar fuel generation mediated by semiconductor heterostructures represents a promising strategy for sustainable energy conversion and storage. The design of semiconductor heterostructures for photocatalytic energy conversion requires the separation of photogenerated charge carriers in real space and their delivery to active catalytic sites at the appropriate overpotentials to initiate redox reactions. Operation of the desired sequence of light harvesting, charge separation, and charge transport events within heterostructures is governed by the thermodynamic energy offsets of the two components and their photoexcited charge-transfer reactivity, which determine the extent to which desirable processes can outcompete unproductive recombination channels. Here, we map energetic offsets and track the dynamics of electron transfer in MoS2/CdS architectures, prepared by interfacing two-dimensional MoS2 nanosheets with CdS quantum dots (QDs), and correlate the observed charge separation to photocatalytic activity in the hydrogen evolution reaction. The energetic offsets between MoS2 and CdS have been determined using hard and soft X-ray photoemission spectroscopy (XPS) in conjunction with density functional theory. A staggered type-II interface is observed, which facilitates electron and hole separation across the interface. Transient absorption spectroscopy measurements demonstrate ultrafast electron injection occurring within sub-5 ps from CdS QDs to MoS2, allowing for creation of a long-lived charge-separated state. The increase of electron concentration in MoS2 is evidenced with the aid of spectroelectrochemical measurements and by identifying the distinctive signatures of electron.phonon scattering in picosecond-resolution transient absorption spectra. Ultrafast charge separation across the type-II interface of MoS2/CdS heterostructures enables a high Faradaic efficiency of similar to 99.4 +/- 1.2% to be achieved in the hydrogen evolution reaction (HER) and provides a 40-fold increase in the photocatalytic activity of dispersed photocatalysts for H-2 generation. The accurate mapping of thermodynamic driving forces and dynamics of charge transfer in these heterostructures suggests a means of engineering ultrafast electron transfer and effective charge separation to design viable photocatalytic architectures.
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