Synchronous Illumination Research Articles

Facial Construction of Hydroxyl Functional Modified Ultrafine BiPO4 with Variation of Dipole Moment Induced by –OH Group

The hydroxyl groups generated by hydrolysis are grafted onto the surface of BiPO4, and a stable surface hydroxylation structure is formed during the subsequent calcination process. This would facilitate the formation of a new hydroxyl functional structure on the surface of the parent photocatalyst without damaging its intrinsic structure. Synchronous illumination X‐Ray photoelectron spectroscopy shows that the hydroxyl functional ultrafine BiPO4 can realize the conversion of defective oxygen to lattice oxygen, which is more conducive in improving the photocatalytic efficiency. The process of filling hydroxyl oxygen vacancies and forming a stable structure is explored using in‐ situ infrared spectroscopy. The induced dipole moment promotes the separation of photogenerated electron–hole pairs, which is beneficial for the enhancement of photocatalytic activity. The dipole moment of the hydroxyl functional‐modified ultrafine BiPO4 is −1.409 D compared to −1.385 D for ordinary BiPO4. The results of this study indicate that hydroxyl functional structure and reduced sample granularity are effective strategies to improve the photocatalytic performance of BiPO4.

Construction of supramolecular S-scheme heterojunctions assisted by hydrogen bond subtle-tuning actuates highly efficient photocatalytic oxidation

Controllable fine-tuning of heterojunction interfaces at the atomic level represents a promising strategy for enhancing semiconductor photocatalytic performance. Herien, we propose a strategy to introduce hydrogen-bonded electron channels at the heterojunction interface to achieve rapid interfacial electron transfer. This S-scheme hydrogen-bonded supramolecular self-assembled H12SubPcB-OPhCH2COOH/Ag3PO4 semiconductor heterojunction exhibits efficient and stable photocatalytic degradation of a wide range of pharmaceuticals and personal care products. Experimental results and theoretical simulations demonstrate that the interface O-H⋅⋅⋅O hydrogen bond at the heterojunction generates an internal electric field, which provides the driving force for accelerated S-scheme charge transfer and enhanced redox properties. Furthermore, the combination of TDDFT calculations and synchronous illumination XPS has revealed that hydrogen bonding acts as a suction electron pump in the excited state, transferring electrons from Ag3PO4 to SubPc-2. These findings suggest that hydrogen-bonded supramolecular semiconductor can be used to develop high-performance photocatalytic materials for environmental remediation.

Hierarchical columnar ZnIn2S4/BiVO4 Z-scheme heterojunctions with carrier highway boost photocatalytic mineralization of antibiotics

How to achieve high-speed directional migration and separation of photogenerated carriers at heterointerfaces is still an important factor restricting efficient photocatalytic reactions. Herein, hierarchical columnar ZnIn2S4/BiVO4 (ZIS/BVO) Z-scheme composite with photogenerated carriers highway in heterogeneous interface are designed by an in situ technique. Ultrathin ZIS nanosheets are uniformly grown upright on the surface of mulberry-like BVO pillars. The confined built-in electric field and Z-scheme heterojunction in ZIS/BVO are verified in detailed by synchronous illumination X-ray photoelectron spectroscopy, theoretical calculation, electron spin resonance spectroscopy, and high-resolution TEM. The photogenerated electrons in the conduction band (CB) of BVO migrate to the valence band (VB) of ZIS through heterojunction, whereas holes in the VB of BVO and electrons in the CB of ZIS maintain the original high redox capability. These holes and electrons with high redox capability react with H2O and O2 to generate more OH and O2−, respectively, achieving enhanced photocatalytic mineralization antibiotic properties. The mineralization rate of antibiotics in the optimized ZIS/BVO material are 4.4 and 1.8 times higher than that of pure BVO and ZIS, respectively.

Enhanced full-spectrum photocatalytic activity of 3D carbon-coated C3N4 nanowires via giant interfacial electric field

Strong interfacial electric field can promote the separation and transfer of photogenerated carriers of photocatalysts. Herein, a three-dimensional (3D) network structure assembled from carbon-coated C3N4 nanowires (denoted as 3D C3N4@C) with a giant interfacial electric field was prepared. The unique 3D structure works with the carbon layer to expand the light absorption range of C3N4 to the full spectrum. Under visible-light irradiation (λ ≥ 420 nm), the degradation rate constants of 3D C3N4@C for bisphenol A and phenol were 41.2 and 5.7 times that of bulk g-C3N4, respectively. Meanwhile, the interfacial electric field of 3D C3N4@C-2 mol/L was 5.14 times that of bulk g-C3N4. The charge transfer process of 3D C3N4@C was confirmed by synchronous illumination X-ray photoelectron spectroscopy and DFT. The significantly improved activity was mainly ascribed to the giant interfacial electric field between g-C3N4 and the carbon layer, which significantly promoted the separation and transportation of photo-generated charge carriers.

Excited Electron‐Rich Bi(3–x)+ Sites: A Quantum Well‐Like Structure for Highly Promoted Selective Photocatalytic CO2 Reduction Performance

AbstractMost of the current research on the photocatalytic mechanism of semiconductors is still on the simulation and evaluation of ground‐state active sites. Insights into photogenerated electron transition paths and excited‐state active sites during photocatalysis are still insufficient. Herein, combining femtosecond time‐resolved transient absorption spectroscopy, in situ Fourier‐transform infrared spectroscopy, synchronous illumination X‐ray photoelectron spectroscopy, and theoretical calculation results rationally reveal that in complex bimetallic oxyhalides the ultrathin rich oxygen vacancies (ROV) PbBiO2Cl (PBOC) double unit cell (DUC) layers facilitate migration and separation of photogenerated electrons from the bulk to Bi sites near the surface oxygen vacancies (OVs), then form the excited electron‐rich Bi(3–x)+ sites like quantum well structure. The excited Bi(3–x)+ sites act as wells for photogenerated electrons leading to lower energy barrier in the rate determining step for the formation of *CO from *COOH intermediate. Without photosensitizers and sacrificial agents, ROV DUC PBOC exhibit high CO generation rate (16.02 µmol h–1 g–1) that is 18 times higher than that of bulk PBOC. In situ characterization combined with theoretical calculation provides effective insight into the photocatalytic mechanism of photoexcited semiconductor materials.

A novel Cl- modification approach to develop highly efficient photocatalytic oxygen evolution over BiVO4 with AQE of 34.6%

Abstract Water oxidation with multielectron transfer is regarded as the crucial step in photocatalytic water splitting. However, a facile but efficient method to promote its slow kinetics is still highly demanding. This work demonstrates that Cl- surface modification drastically enhances photocatalytic water oxidation over BiVO4 as well as WO3. The optimal modified BiVO4 achieves a photocatalytic activity of 4.2 orders enhancement relative to the pristine BiVO4, giving up to an excellent apparent quantum efficiency of 34.6% at 420 nm. Cl--modified 30-facet BiVO4 with 2.6 times enhancement confirms that the surface reaction involved with photogenerated holes can be dramatically accelerated by Cl- modification in addition to enhanced charge carrier separation. Our results highlight the impact of Cl- modification on the reaction kinetics and pathway during the photocatalytic water oxidation process, which has been mostly overlooked. Systematic studies (DFT simulations, kinetic experiments) reveal that Cl- modification remarkably reduces the photocatalytic water oxidation energy barrier and alters reaction pathway, which is also manifested in facilitated H2O molecule activation in synchronous illumination XPS (SI-XPS) study. The EXAFS and angle-resolved XPS (AR-XPS) results show that Cl bonds to Bi and mainly concentrates on the surface of modified BiVO4. Our findings provide an effective and facile approach to exploring efficient O2 evolution semiconductors for photocatalytic water splitting.

Direct Observation of Dynamic Bond Evolution in Single‐Atom Pt/C3N4 Catalysts

AbstractSingle‐atom catalysts are promising platforms for heterogeneous catalysis, especially for clean energy conversion, storage, and utilization. Although great efforts have been made to examine the bonding and oxidation state of single‐atom catalysts before and/or after catalytic reactions, when information about dynamic evolution is not sufficient, the underlying mechanisms are often overlooked. Herein, we report the direct observation of the charge transfer and bond evolution of a single‐atom Pt/C3N4 catalyst in photocatalytic water splitting by synchronous illumination X‐ray photoelectron spectroscopy. Specifically, under light excitation, we observed Pt−N bond cleavage to form a Pt0 species and the corresponding C=N bond reconstruction; these features could not be detected on the metallic platinum‐decorated C3N4 catalyst. As expected, H2 production activity (14.7 mmol h−1 g−1) was enhanced significantly with the single‐atom Pt/C3N4 catalyst as compared to metallic Pt‐C3N4 (0.74 mmol h−1 g−1).

Direct Observation of Dynamic Bond Evolution in Single-Atom Pt/C3 N4 Catalysts.

Single-atom catalysts are promising platforms for heterogeneous catalysis, especially for clean energy conversion, storage, and utilization. Although great efforts have been made to examine the bonding and oxidation state of single-atom catalysts before and/or after catalytic reactions, when information about dynamic evolution is not sufficient, the underlying mechanisms are often overlooked. Herein, we report the direct observation of the charge transfer and bond evolution of a single-atom Pt/C3 N4 catalyst in photocatalytic water splitting by synchronous illumination X-ray photoelectron spectroscopy. Specifically, under light excitation, we observed Pt-N bond cleavage to form a Pt0 species and the corresponding C=N bond reconstruction; these features could not be detected on the metallic platinum-decorated C3 N4 catalyst. As expected, H2 production activity (14.7 mmol h-1 g-1 ) was enhanced significantly with the single-atom Pt/C3 N4 catalyst as compared to metallic Pt-C3 N4 (0.74 mmol h-1 g-1 ).

Direct Observation of Oxygen Vacancy Self‐Healing on TiO2 Photocatalysts for Solar Water Splitting

AbstractOxygen vacancy (Vo) on transition metal oxides plays a crucial role in determining their chemical/physical properties. Conversely, the capability to directly detect the changing process of oxygen vacancies (Vos) will be important to realize their full potentials in the related fields. Herein, with a novel synchronous illumination X‐ray photoelectron spectroscopy (SI‐XPS) technique, we found that the surface Vos (surf‐Vos) exhibit a strong selectivity for binding with the water molecules, and sequentially capture an oxygen atom to achieve the anisotropic self‐healing of surface lattice oxygen. After this self‐healing process, the survived subsurface Vos (sub‐Vos) promote the charge excitation from Ti to O atoms due to the enriched electron located on low‐coordinated Ti sites. However, the excessive sub‐Vos would block the charge separation and transfer to TiO2 surfaces resulted from the destroyed atomic structures. These findings open a new pathway to explore the dynamic changes of Vos and their roles on catalytic properties, not only in metal oxides, but in crystalline materials more generally.

Direct Observation of Oxygen Vacancy Self-Healing on TiO2 Photocatalysts for Solar Water Splitting.

Oxygen vacancy (Vo) on transition metal oxides plays a crucial role in determining their chemical/physical properties. Conversely, the capability to directly detect the changing process of oxygen vacancies (Vos) will be important to realize their full potentials in the related fields. Herein, with a novel synchronous illumination X-ray photoelectron spectroscopy (SI-XPS) technique, we found that the surface Vos (surf-Vos) exhibit a strong selectivity for binding with the water molecules, and sequentially capture an oxygen atom to achieve the anisotropic self-healing of surface lattice oxygen. After this self-healing process, the survived subsurface Vos (sub-Vos) promote the charge excitation from Ti to O atoms due to the enriched electron located on low-coordinated Ti sites. However, the excessive sub-Vos would block the charge separation and transfer to TiO2 surfaces resulted from the destroyed atomic structures. These findings open a new pathway to explore the dynamic changes of Vos and their roles on catalytic properties, not only in metal oxides, but in crystalline materials more generally.

Photo-controlled bond changes on Pt/TiO2 for promoting overall water splitting and restraining hydrogen–oxygen recombination

Photo-induced chemical-bond reconstruction processes at Pt/TiO2 photocatalytic interfaces have been detected for the first time via synchronous illumination X-ray photoelectron spectroscopy combined with an angle-resolved technique.

Relationship between interatomic electron transfer and photocatalytic activity of TiO2

We demonstrate the direct observation of interatomic electron excitation and transfer on single-crystal TiO2 (001) surface for water splitting by a synchronous illumination X-ray photoelectron spectroscopy (SI-XPS). The quantitative results clearly reveal that the initially absorbed water molecules on TiO2 surface promote the electron transfer between Ti and O atoms. However, when water molecule was dissociated into OH and H groups on Ti and O sites, respectively, the electron excitation and transfer ability have been gradually decreased and finally terminated, probably due to the reverse electron-attraction of OH group on Ti atoms. Amazingly, when Pt co-catalyst was deposited on TiO2, the electron excitation between Ti and O atoms have been significantly enhanced and no evident decrease has been observed during the entire water splitting process. In addition, the changes of Pt–O and Ti–O chemical bonds at the photocatalytic interfaces have been also detected. Furthermore, based on the above mechanism studies, the photocatalytic hydrogen production system for Pt/R-TiO2 (001) in KOH solution containing CH3OH was proposed, which exhibits a significant enhancement of hydrogen evolution rate (20.78 μmol h−1), which is nearly 2.5 times higher than that of traditional Pt/R-TiO2 (001) in CH3OH system (8.35 μmol h−1). The finding in this work may pave the way for developing other high-efficiency photocatalytic hydrogen production system over TiO2-based photocatalysts.

Laser line scan underwater imaging by complementary metal–oxide–semiconductor camera

This work employs the complementary metal–oxide–semiconductor (CMOS) camera to acquire images in a scanning manner for laser line scan (LLS) underwater imaging to alleviate backscatter impact of seawater. Two operating features of the CMOS camera, namely the region of interest (ROI) and rolling shutter, can be utilized to perform image scan without the difficulty of translating the receiver above the target as the traditional LLS imaging systems have. By the dynamically reconfigurable ROI of an industrial CMOS camera, we evenly divided the image into five subareas along the pixel rows and then scanned them by changing the ROI region automatically under the synchronous illumination by the fun beams of the lasers. Another scanning method was explored by the rolling shutter operation of the CMOS camera. The fun beam lasers were turned on/off to illuminate the narrow zones on the target in a good correspondence to the exposure lines during the rolling procedure of the camera’s electronic shutter. The frame synchronization between the image scan and the laser beam sweep may be achieved by either the strobe lighting output pulse or the external triggering pulse of the industrial camera. Comparison between the scanning and nonscanning images shows that contrast of the underwater image can be improved by our LLS imaging techniques, with higher stability and feasibility than the mechanically controlled scanning method.

Facile Fabrication of Nanoporous Bi2WO6 Photoanodes for Efficient Solar Water Splitting

AbstractNanoporous bismuth tungsten oxide (Bi2WO6) photoanodes are synthesized by using a facile drop‐casting strategy for one‐step fabrication. The Bi2WO6 photoanode exhibits significantly improved solar photo‐electrochemical capability for water oxidation. The photocurrent density is nearly 10 times higher than the traditional particle photoanodes. In addition, synchronous illumination X‐ray photoelectron spectroscopy (SIXPS) was employed to directly identify the charge separation and electron transfer in the nanoporous Bi2WO6 photoanodes, which clearly reveals that the electrons transfer from the Bi and W atomic sites to the O sites. These demonstrations provide further new insights into the origin of high efficiency in nanoporous photoanodes, which may be promising for the rational construction of solar conversion and storage devices.

The charge transfer mechanism of Bi modified TiO2 nanotube arrays: TiO2 serving as a “charge-transfer-bridge”

The surface of Bi nanoparticles would be oxidized to amorphous Bi2O3 layer with thickness about 7nm in the air. Until now, it is still unclear about the different roles of Bi and Bi2O3 in the photocatalysis when Bi nanoparticles are deposited on semiconductors. In this work, Bi nanospheres have been decorated on the top aperture of TiO2 nanotube arrays by vapor deposition method, and an X-ray photoelectron spectroscopy combined with synchronous illumination technique is applied to explore the charge transfer mechanism. Under visible light, the electrons generated from the surface plasmon resonance of Bi would transfer to the conduction band of TiO2 first, and then migrate to the oxide surface of Bi2O3 and reduce it to metallic Bi. During this process, TiO2 serves as a “charge-transfer-bridge” and the reductive reaction would not occur in the absence of it. And the energy of the immigrant electrons differs from the self-excited ones, which can not trigger the reductive reaction. These findings have resolved the puzzles about the utilization of Bi, and figured out the different roles of Bi and Bi2O3 in the photocatalytic process. Furthermore, the photoelectrochemical activities of Bi modified TiO2 nanotubes arrays have been systematically explored and it is found that the photocurrent of TiO2 nanotube arrays could be significantly improved due to the surface plasmon resonance of Bi as well as the optimized charge transfer and transport characteristics.

Direct Observation of Charge Separation on Anatase TiO2 Crystals with Selectively Etched {001} Facets.

Synchronous illumination X-ray photoelectron spectroscopy (SIXPS) was employed for the first time to directly identify the photogenerated charge separation and transfer on anatase TiO2 single-crystals with selectively etched {001} facets. More specifically, for the TiO2 crystals with intact {001} and {101} facets, most of photogenerated charge carriers rapidly recombined, and no evident electron-hole separation was detected. With selectively etching on {001} facets, high efficient charge separation via hole transfer to titanium and electron to oxygen was clearly observed. However, when the {001} facets were completely etched into a hollow structure, the recombination for photogenerated electron-hole pairs would dominate again. These demonstrations clearly reveal that the appropriate corrosion on {001} facets could facilitate more efficient electron-hole separation and transfer. As expected, the optimized TiO2 microcrystals with etched {001} facets could achieve a hydrogen generation rate of 74.3 μmol/h/g, which is nearly 7 times higher than the intact-TiO2 crystals.

Reprint of “Breathing and sense of self: Visuo-respiratory conflicts alter body self-consciousness”

Bodily self-consciousness depends on the processing of interoceptive and exteroceptive signals. It can be disrupted by inducing signal conflicts. Breathing, at the crossroad between interoception and exteroception, should contribute to bodily self-consciousness. We induced visuo-respiratory conflicts in 17 subjects presented with a virtual body or a parallelepidedal object flashing synchronously or asynchronously with their breathing. A questionnaire detected illusory changes in bodily self-consciousness and breathing agency (the feeling of sensing one's breathing command). Changes in self-location were tested by measuring reaction time during mental ball drop (MBD). Synchronous illumination changed the perceived location of breathing (body: p=0.008 vs. asynchronous; object: p=0.013). It resulted in a significant change in breathing agency, but no changes in self-identification. This was corroborated by prolonged MBD reaction time (body: +0.045s, 95%CI [0.013; 0.08], p=0.007). We conclude that breathing modulates bodily self-consciousness. We also conclude that one can induce the irruption of unattended breathing into consciousness without modifying respiratory mechanics or gas exchange.

Breathing and sense of self: Visuo–respiratory conflicts alter body self-consciousness

Bodily self-consciousness depends on the processing of interoceptive and exteroceptive signals. It can be disrupted by inducing signal conflicts. Breathing, at the crossroad between interoception and exteroception, should contribute to bodily self-consciousness. We induced visuo-respiratory conflicts in 17 subjects presented with a virtual body or a parallelepidedal object flashing synchronously or asynchronously with their breathing. A questionnaire detected illusory changes in bodily self-consciousness and breathing agency (the feeling of sensing one's breathing command). Changes in self-location were tested by measuring reaction time during mental ball drop (MBD). Synchronous illumination changed the perceived location of breathing (body: p=0.008 vs. asynchronous; object: p=0.013). It resulted in a significant change in breathing agency, but no changes in self-identification. This was corroborated by prolonged MBD reaction time (body: +0.045s, 95%CI [0.013; 0.08], p=0.007). We conclude that breathing modulates bodily self-consciousness. We also conclude that one can induce the irruption of unattended breathing into consciousness without modifying respiratory mechanics or gas exchange.

Bodily reactions to music: Emotions and preference

Bodily self-consciousness depends on the processing of interoceptive and exteroceptive signals. It can be disrupted by inducing signal conflicts. Breathing, at the crossroad between interoception and exteroception, should contribute to bodily self-consciousness. We induced visuo-respiratory conflicts in 17 subjects presented with a virtual body or a parallelepidedal object flashing synchronously or asynchronously with their breathing. A questionnaire detected illusory changes in bodily self-consciousness and breathing agency (the feeling of sensing one's breathing command). Changes in self-location were tested by measuring reaction time during mental ball drop (MBD). Synchronous illumination changed the perceived location of breathing (body: p = 0.008 vs. asynchronous; object: p = 0.013). It resulted in a significant change in breathing agency, but no changes in self-identification. This was corroborated by prolonged MBD reaction time (body: +0.045 s, 95%CI [0.013; 0.08], p = 0.007). We conclude that breathing modulates bodily self-consciousness. We also conclude that one can induce the irruption of unattended breathing into consciousness without modifying respiratory mechanics or gas exchange.

Effect of light quality on chloroplast-membrane organization and function in pea

The effect of light quality during plant growth of chloroplast membrane organization and function in peas (Pisum sativum L. cv. Alaska) was investigated. In plants grown under photosystem (PS) I-enriched (far-red enriched) illumination both the PSII/PSI stoichiometry and the electrontransport capacity ratios were high, about 1.9. In plants grown under PSII-enriched (far-red depleted) illumination both the PSII/PSI stoichiometry and the electron-transport capacity ratios were significantly lower, about 1.3. In agreement, steady-state electron-transport measurements under synchronous illumination of PSII and PSI demonstrated an excess of PSII in plants grown under far-red-enriched light. Sodium dodecylsulfate polyacrylamide gel electrophoretic analysis of chlorophyll-containing complexes showed greater relative amounts of the PSII reaction center chlorophyll-protein complex in plants grown under farred-enriched light. Additional changes were observed in the ratio of light-harvesting chlorophyll a/b protein to PSII reaction center chlorophyll-protein under the two different light-quality regimes. The results demonstrate the dynamic nature of chloroplast structure and support the notion that light quality is an important factor in the regulation of chloroplast membrane organization and-function.