Abstract
Natural photosynthesis proceeded by sequential water splitting and CO
2
reduction reactions is an efficient strategy for CO
2
conversion. Here, mimicking photosynthesis to boost CO
2
-to-CO ...conversion is achieved by using plasmonic Bi as an electron-proton-transfer mediator. Electroreduction of H
2
O with a Bi electrode simultaneously produces O
2
and hydrogen-stored Bi (Bi-H
x
). The obtained Bi-H
x
is subsequently used to generate electron-proton pairs under light irradiation to reduce CO
2
to CO; meanwhile, Bi-H
x
recovers to Bi, completing the catalytic cycle. This two-step strategy avoids O
2
separation and enables a CO production efficiency of 283.8 μmol g
−1
h
−1
without sacrificial reagents and cocatalysts, which is 9 times that on pristine Bi in H
2
gas. Theoretical/experimental studies confirm that such excellent activity is attributed to the formed Bi-H
x
intermediate that improves charge separation and reduces reaction barriers in CO
2
reduction.
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•Size-selected Pt modified g-C3N4 was fabricated by in-situ photoreduction method.•Pt0.1-CN with single-atom Pt shows pronounced photocatalytic hydrogen evolution.•Pt0.1-CN exhibits ...H2 generation up to 473.82 µmol mg−1 pt under visible light.•Enhanced performance is due to the synergistic effect of Pt single-atom.
Graphitic carbon nitride (g-C3N4) with Pt co-catalyst was synthesized by in-situ photoreduction and used as a visible light photocatalyst. The size of Pt co-catalyst can be controlled form single atoms to nano-clusters by the induced amount of Pt precursor. The results indicated that compared with nano-clusters, the Pt0.1-CN (with 0.1 wt% Pt loading amount) which is characterized as single-atom Pt exhibits a pronounced photocatalytic hydrogen evolution capability. For Pt0.1-CN with single-atom Pt as co-catalyst, the H2 generation is up to 473.82 µmol mg−1pt under visible light irradiation (λ > 420 nm). The enhanced photocatalytic performance is mainly attributed to the synergistic effect of high light adsorption efficiency, effective charge separation, and high dispersed active sites of Pt atoms. The results of this work highlighted that loading g-C3N4 with Pt single atoms will achieve a maximum utilization efficiency of Pt atoms and an improvement photocatalytic performance.
Current plasmonic photocatalysts are mainly based on noble metal nanoparticles and rarely work in the infrared (IR) light range. Herein, cost‐effective Bi2O3−x with oxygen vacancies was formed in ...situ on commercial bismuth powder by calcination at 453.15 K in atmosphere. Interestingly, defects introduced into Bi2O3−x simultaneously induced a localized surface plasmon resonance (LSPR) in the wavelength range of 600–1400 nm and enhanced the adsorption for CO2 molecules, which enabled efficient photocatalysis of CO2‐to‐CO (ca. 100 % selectivity) even under low‐intensity near‐IR light irradiation. Significantly, the apparent quantum yield for CO evolution at 940 nm reached 0.113 %, which is approximately 4 times that found at 450 nm. We also showed that the unique LSPR allows for the realization of a nearly linear dependence of photocatalytic CO production rate on light intensity and operating temperature. Finally, based on an IR spectroscopy study, an oxygen‐vacancy induced Mars‐van Krevlen mechanism was proposed to understand the CO2 reduction reactions.
Bifunctional oxygen defects were created on noble‐metal‐free Bi2O3−x, which enables noble‐metal‐like localized surface plasmon resonance and enhanced CO2 adsorption properties. As a result, photocatalytic CO2‐to‐CO conversion with approximately 100 % selectivity was realized even under low‐intensity light at 940 nm, showing a quantum efficiency of 0.113 % that is 4.0 times of that at 450 nm.
Abstract
Achieving CO
2
reduction with H
2
O on metal photocatalysts and understanding the corresponding mechanisms at the molecular level are challenging. Herein, we report that quantum-sized Au ...nanoparticles can photocatalytically reduce CO
2
to CO with the help of H
2
O by electron-hole pairs mainly originating from interband transitions. Notably, the Au photocatalyst shows a CO production rate of 4.73 mmol g
−1
h
−1
(~100% selectivity), ~2.5 times the rate during CO
2
reduction with H
2
under the same experimental conditions, under low-intensity irradiation at 420 nm. Theoretical and experimental studies reveal that the increased activity is induced by surface Au–O species formed from H
2
O decomposition, which synchronously optimizes the rate-determining steps in the CO
2
reduction and H
2
O oxidation reactions, lowers the energy barriers for the *CO desorption and *OOH formation, and facilitates CO and O
2
production. Our findings provide an in-depth mechanistic understanding for designing active metal photocatalysts for efficient CO
2
reduction with H
2
O.
Inspired by natural photosynthesis, a new series of Z-scheme CdxZn1-xS/Au/g-C3N4 photocatalysts were synthesized via depositing Au particles on g-C3N4, followed by anchoring CdxZnl xS solid solution ...on the pre-formed Au/g-C3N4 for photocatalytic hydrogen evolution. Their structure, morphology and optical property were investigated in detail. Photocatalytic activities of the developed photocatalysts for water splitting were evaluated under visible-light irradiation （2 〉 420 nm） using glucose as electron donor. The highest hydrogen evolution rate of 123 μmol g^-1 h^-1 is achieved by Cdo.sZno.2S/Au/g-C3N4, which is 52.2 and 8.63 times higher than that of Au/g-C3N4 and CdS/Au/g-C3N4, respectively. The results of pho- toluminescence spectra, photoelectrochemical and time-resolved photoluminescence spectra indicate that the improved photocatalytic activities for CdxZn1-xSAu/g-C3N4 are due to the efficient separation of photogenerated carriers. In addition, it is noteworthy that the undesired byproducts CO and CO2 are greatly reduced by introducing CdxZn1-xS over Au/g-C3N4 surface. In the photocatalytic process, gluconic acid originated from the reaction of photogenerated hydroxyl radical with glucose plays a vital role on suppressing the formation of the gas byproducts. The present work will provide a new strategy to design Z-scheme photocatalysts with enhanced efficiency for water splitting along with suppressing the byproducts.
Surface-Ti-rich SrTiO3 exhibits the highest activity for photocatalytic CO2 reduction, which can be ascribed to the enhanced harvesting to simulated solar light, high proportion of active species ...derived from CO2 adsorption on the surface, and Ti-ion exposure.
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•SrTiO3, surface-Ti-rich SrTiO3 and Sr(OH)2-decorated SrTiO3 were prepared.•Surface-Ti-rich SrTiO3 exhibits the highest activity for photocatalytic CO2 reduction.•It is speculated that the only CO2 adsorbed on Ti ions has a higher reactivity under light irradiation.
Perovskite oxide SrTiO3 is a promising semiconductor photocatalyst for CO2 reduction, which has two possible chemical surfaces—TiO2-terminated and SrO-terminated surfaces. Up to now, the effect of chemical surface and its modification on CO2 adsorption, activation and sequential photocatalytic reduction is not established. In the work, SrTiO3, surface-Ti-rich SrTiO3 and Sr(OH)2-decorated SrTiO3 were prepared and their structural, surface, and optical properties and photocatalytic activity were explored. It is found that the absorption edge of surface-Ti-rich SrTiO3 shifted toward visible-light region as compared with that of the other two photocatalysts, which is attributed to the decreased Ti 3d ground-state level at the surface. Bicarbonate- (HCO3−) and bidentate carbonate-like (b-CO3=) species are the main species for CO2 adsorption on the surface-Ti-rich SrTiO3, whereas, besides HCO3− and b-CO3=, plenty of monodentate carbonate-like species (m-CO3=) that has relatively low reactivity is present on the SrTiO3 and Sr(OH)2-decorated photocatalysts. As a result, the surface-Ti-rich SrTiO3 exhibits the highest activity for CO2 reduction. Furthermore, although Sr(OH)2-decoration and SrO-terminated surfaces facilitate CO2 fixing, the produced surface species are attached to the weakly active Sr ions, giving rise to the lower reactivity. The present work might supply a guide for designing highly active perovskite–type semiconductors for photocatalysis.
Different lengths of rutile TiO2 nanowires (NW) with wide-open space for effective material filling were used as photoanodes for perovskite solar cells. Cells with 900 nm nanowires as photoanodes ...exhibit a current density of 22 mA cm(-2) and an efficiency of 11.7%, outperforming the reported TiO2 nanowire-based perovskite solar cells.
The black TiO2–coated Cu nanoparticles with oxygen resistance were fabricated in this work. The activity of Cu@TiO2 for CO2 photoreduction under visible-light irradiation is markedly higher than that ...of bared black TiO2
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•Fabrication of black TiO2–coated Cu nanoparticles with oxygen resistance of metallic Cu.•The metallic Cu nanoparticles promote the formation of oxygen vacancies in TiO2 through the metal-oxide interaction.•The metallic Cu nanoparticles facilitate the separation of photogenerated electron-hole pairs of TiO2.•black TiO2–coated Cu photocatalysts exhibit higher activity for the reduction of CO2 than that of TiO2.
Nanosized metallic copper could be a replacement of noble metals for improving photoactivity of TiO2-based photocatalysts, but it tends to be oxidized by oxygen in surroundings. To avoid this, black TiO2−coated Cu nanoparticles (denoted as Cu@TiO2) were constructed in the present work, and their photoactivity for the photoreaction of CO2 with H2O vapor under visible-light irradiation was explored. X-ray diffraction, transmission electron microscopy and selected area electron diffraction analysis for the used Cu@TiO2 confirm the hierarchical structure of Cu@TiO2 and oxygen resistance of metallic Cu. The photocatalytic activity for Cu@TiO2 (∼4%Cu) reaches 1.7 times of that for its counterpart, bared black TiO2. The improved photoactivity is attributed to the embedded metallic Cu, which promotes the formation of oxygen vacancies in TiO2 through the metal-oxide interaction, thus increasing the visible-light absorption of Cu@TiO2 and the adsorption of CO2 on their surface. Furthermore, the metallic Cu increases photoinduced charge-separation of TiO2 through trapping electrons as evidenced by transient photocurrent measurements. The present work sheds light on developing new type of metal-oxide based visible-light-driven photocatalysts.
Formaldehyde (HCHO), as one of the main indoor toxic pollutions, presents a great threat to human health. Hence, it is imperative to efficiently remove HCHO and create a good indoor living ...environment for people. Herein, a layered perovskite material SrBi2Ta2O9 (SBT), was studied for the first time and exhibited superior photocatalytic efficiency and stability compared to commercial TiO2 (P25). Furthermore, a unique dark–light tandem catalytic mechanism was constructed. In the dark reaction stage, HCHO (Lewis base) site was adsorbed on the terminal (Bi2O2)2+ layer (Lewis acid) site of SBT in the form of Lewis acid-base complexation and was gradually oxidized to CO32− intermediate (HCHO → DOM (dioxymethylene) → HCOO− → CO32−). Then, in the light reaction stage, CO32− was completely converted into CO2 and H2O (CO32− → CO2). Our study contributes to a thorough comprehension of the photocatalytic oxidation of HCHO and points out its potential for day–night continuous work applications in a natural environment.
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