RESUMO
Designing of heterojunction photocatalysts with appropriate interfacial contact plays crucial roles in enhancing the interfacial charge transfer/separation. A two-dimensional (2D)/2D face-to-face heterojunction is an ideal option since this architecture with a large contact area can provide abundant reactive centers and promote the interfacial charge transfer/separation between layers. Herein, a novel 2D/2D heterojunction of NiFe-layered double hydroxides (NiFe-LDH)/Cs2AgBiBr6 (CABB) was fabricated by electrostatic self-assembly of NiFe-LDH and CABB nanosheets. This unique 2D/2D architecture endowed NiFe-LDH/CABB with a large contact area and a short charge transport distance, assuring remarkable interfacial charge transfer/separation rates. As a result, the 2D/2D NiFe-LDH/CABB heterojunction exhibited significant improvement in photocatalytic CO2 reduction under visible light than the pristine counterparts. Based on density functional theory calculations and various characterizations, a step scheme charge-transfer mechanism was proposed. This investigation sheds light on the designing and manufacturing of highly efficient 2D/2D heterostructure photocatalysts for artificial photosynthesis.
RESUMO
The rational design of a two-dimensional (2D)/2D "face-to-face" heterojunction photocatalyst is crucial for the mediation of interfacial charge transfer/separation. Herein, a unique 2D/2D step-scheme (S-scheme) photocatalyst of CsPbBr3/BiOCl is constructed by the self-assembly of CsPbBr3 and BiOCl nanosheets (NSs). Profiting from the effective interface contact and appropriate band structures between CsPbBr3 and BiOCl NSs, a valid S-scheme heterojunction of CsPbBr3/BiOCl is established. Density functional theory (DFT) calculations and a series of characterization techniques including X-ray photoelectron spectra (XPS), photoassisted Kelvin probe force microscopy (KPFM), and electron spin resonance (ESR) systematically corroborate the S-scheme charge-transfer mechanism between CsPbBr3 and BiOCl. The formation of an S-scheme heterojunction endows the photocatalyst with boosted charge separation and retainment of the highest redox ability. As a result, the obtained 2D/2D CsPbBr3/BiOCl S-scheme photocatalyst shows much superior CO2-reduction performance to single CsPbBr3 and BiOCl. This investigation provides new insights into the construction of novel S-scheme heterojunctions based on 2D/2D photocatalytic systems.
RESUMO
Heterojunction construction, especially the inorganic/organic hybrids, is regarded as a universal and effective strategy to achieve high-performance photocatalysts. Herein, a 2D/2D inorganic/organic hybrid photocatalyst was constructed by the electrostatic self-assembly of the lead-free double-perovskite of Cs2AgBiBr6 nanosheets (NSs) and covalent triazine framework (CTF) NSs. The resultant Cs2AgBiBr6/CTF-1 (CABB/CTF-1) hybrid possessed a large surface-to-surface contact area, ensuring intimate interfacial interaction and efficient charge transfer/separation. Meanwhile, the periodical pore structure of CTF-1 endowed the CABB/CTF-1 hybrid with enhanced CO2 adsorption/activation capacity. Consequently, the 2D/2D CABB/CTF-1 hybrid exhibited a remarkable photocatalytic performance toward CO2 reduction. Based on the band structure analysis and various characterization techniques, for example, X-ray photoelectron spectra and electron spin resonance, an S-scheme charge transfer mechanism was proposed. This study presents a new protocol for designing 2D/2D inorganic/organic hybrid photocatalytic systems, which hold great potentials in solar fuel applications.
RESUMO
Perovskite CsPbBr3 nanocrystals (NCs) have emerged as promising candidates for the photocatalytic reduction of CO2. However, the CO2 conversion efficiency of pristine CsPbBr3 is still unsatisfactory, mainly due to severe radiative recombination, poor stability and low CO2 capturing ability. Coincidentally, nanoporous carbon powder (NCP) has received tremendous attention for environmental remediation and renewable energy production. Herein, by immobilizing CsPbBr3 NCs into the pores of NCP, a CsPbBr3/NCP hybrid has been successfully constructed for the first time, which combined the advantages of CsPbBr3 NCs and NCP. In comparison with pristine CsPbBr3, the resultant hybrid photocatalyst exhibited much superior photocatalytic performance in CO2 reduction, which could be attributed to the enhanced electron extraction and transfer between CsPbBr3 NCs and NCP, higher CO2 capturing ability and more active sites for CO2 activation. Furthermore, the nanohybrid displayed remarkable reusability in photocatalytic CO2 reduction. This study is anticipated to provide a new pathway for the design and fabrication of high-performance photocatalysts based on perovskites for solar-energy-conversion applications.
RESUMO
Over the last 5 years, metal halide perovskites (MHPs) have emerged as promising photocatalysts for CO2 reduction because of their extraodinary visible-light-harvesting capabilities and appropriate band structure. However, the CO2 photoreduction activity of pristine MHPs is still unsatisfactory because of the phase instability, serious radiative recombination, and insufficient surface-active sites. This Perspective summarizes the strategies employed in recent studies for enhancing the photocatalytic CO2 reduction performance of MHPs from the standpoint of structure engineering, which includes composition/dimension regulation, surface modification, and heterostructure construction. The relationship between the structure (composition, dimension, and shape) and photocatalytic performance is established, which is instructive for exploiting highly efficient perovskite-based photocatalysts in artificial photosynthesis applications. Further, some important challenges and future prospects of MHPs in this field are proposed and discussed.