The photocatalytic reduction of CO2 into high-value-added fuels is an extremely desirable process, but its practical application is limited by the weak adsorption and activation of inert CO2 ...molecules. Herein, oxygen vacancies (VOs) are formed on SrBi2Ta2O9 (SBT) by annealing in Ar gas at 400 °C and can spontaneously react with adsorbed H2O to form surface hydroxyls. Therefore, frustrated Lewis pairs (FLPs) are fabricated on SBT, where the surface VO and proximal surface hydroxyl serve as the Lewis acid and base, respectively. Experimental results indicate that the obtained FLPs can act as catalytic sites to adsorb, activate, and convert CO2 under low-intensity LED light irradiation (420 nm). Consequently, a CO2-to-CO conversion rate of 9.9 μmol g–1 h–1 is achieved in pure water on VO-SBT-OH without any sacrificial agents or cocatalysts, which is ∼4× higher than that of pristine SBT. Moreover, the surface hydroxyl can self-replenish by dissociating H2O during the reaction, thereby achieving a long-term CO2 conversion for 60 h. Our study demonstrates the potential of FLPs as a platform to decrease barriers to reducing CO2 and provides valuable insights into the underlying photocatalytic mechanism.
Combining piezoelectric effect and persulfate (PS) activation is a newly developed strategy for refractory emerging contaminants removal. In this work, borate SrBi2B2O7 (SBBO) is firstly developed as ...a piezoelectric material to piezo-assisted activation of PS for the removal of sulfadiazine (SDZ) under ultrasonic irradiation (US). SDZ could be efficiently degraded by 85.61 % in the system of PS/SBBO/US with a pseudo-first-order rate constant of 0.0520 min−1, which is faster than that in the systems of PS/SBBO (0.0210 min−1), SBBO/US (0.0041 min−1), PS/US (0.0074 min−1), and PS/BaTiO3/US (0.0120 min−1). The excellent degradation performance of the PS/SBBO/US system is mainly attributed to the piezoelectric effect of the SBBO which plays an important role in PS activation and accelerating reaction. Two oxidation processes, radical process (•O2- and •SO4-) and non-radical process (1O2 and electron transfer), exist during the SDZ degradation. The system of PS/SBBO/US also attains excellent removal efficiency in different SDZ contained water bodies. The possible degradation pathways mainly include cleavage of bonds, ring-opening, and hydroxylation process, and the toxicity of intermediates was predicted by T.E.S.T. software. This study provides new insight into piezoelectric catalysis associated with PS activation for SDZ removal.
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•Piezo-promoted PS activation by SBBO exhibited an excellent catalytic performance.•The degradation process existed radical and non-radical process.•The mechanism of piezo-promoted PS activation was clarified.•The possible degradation pathway of sulfadiazine based on LC-MS was proposed.•The toxicity of intermediates was evaluated by T.E.S.T. software.
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•Superior piezo-photocatalytic response BFO@SBBO heterojunction was successfully fabricated.•The polarization electric field across the p-n heterojunction remarkably improves the ...separation of photogenerated charge carriers.•Further addition of PS intensifies charge separation and visible light utilization.•1O2 dominate BPA removal in the piezo-photocatalytic reaction.•BFO@SBBO demonstrates excellent performance and high stability in remediating BPA and actual phenolic wastewater.
Photoresponse piezoelectric materials have attracted tremendous interest as a new generation of photocatalysts for water purification. However, the development of durable and efficient piezo-photocatalyst remains to be a challenging task. Herein, a novel BiFeO3@SrBi2B2O7 (BFO@SBBO) p-n heterojunction with ultrahigh piezo-photocatalytic ability was fabricated after adjustment of BFO outer layer thickness, and utilized to activate persulfate (PS) for efficient water decontamination. The synergistic effect between the internal electric field across the heterojunction and the PS greatly improves the separation of photogenerated charge carriers. In the presence of ultrasonic mechanical vibration, 10 mg/L bisphenol A (BPA) was completely removed within 20 min with the assistance of a low dosage of PS upon visible light irradiation, which outperform various piezo-photocatalysts. Transformation and contribution of reactive oxygen species (ROSs, i.e., OH, O2−, 1O2 and SO4−) generated in the BFO@SBBO/US/Vis/PS system were evaluated and semi-quantified to understand the mechanism of BPA piezo-photocatalytic degradation. The stability and performance of BFO@SBBO piezo-photocatalysis toward typical organic pollutants and actual phenolic water remediation were evaluated, which confirmed the promising practical potential of BFO@SBBO in water remediation. This study offers a new insight into strategies for highly efficient piezo-photocatalyst for photocatalytic water remediation.
High efficient photocatalytic reduction of 4-nitroaniline to
p-phenylenediamine over microcrystalline SrBi
2Nb
2O
9 was observed upon purging with N
2 under UV-light irradiation. Its photocatalytic ...activity was higher than that of sample P25 (commercial TiO
2, Degussa Co.). The analysis results of X-ray diffraction and X-ray photoelectron spectroscopy revealed that microcrystalline SrBi
2Nb
2O
9 had high stability for the photocatalytic reduction of 4-nitroaniline. Further experiments indicated that ammonium oxalate was indispensable for the photocatalytic reduction of 4-nitroaniline. Moreover, the high efficient photocatalytic reduction of 4-nitroaniline over microcrystalline SrBi
2Nb
2O
9 might be ascribed to its relatively high conduction band.
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► Photocatalytic reduction of 4-nitroaniline over SrBi
2Nb
2O
9 microcrystal was observed. ► Its photocatalytic activity was higher than that of commercial TiO
2 under UV light. ► The higher catalytic activity was attributed to its relatively high conduction band.
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•Pt nanoparticles (NPs) were successfully loaded onto several atomic-layer-thick SrBi4Ti4O15 (SBTO) nanosheets via an efficient preparation method.•The average hydrogen evolution rate ...of SBTO-Pt-6 wt% is ∼ 3700 μmol g-1h−1, which exceeds that of many ferroelectric catalysts.•DFT calculations showed that added Pt NPs are active sites for hydrogen evolution.•Localized surface plasmon resonance effects as well as excellent electron trapping ability of Pt NPs play crucial roles.
Combining metal with ferroelectrics is one of the reliable strategies to enhance the photocatalytic water splitting of ferroelectrics dramatically. However, the metal loading ratio is directly related to the synergistic effect of catalysts. In order to find the appropriate loading of Pt, we fabricated SrBi4Ti4O15 (SBTO) nanosheets (NSs) and deposited different amounts of Pt nanoparticles (NPs) to form heterojunction. The optoelectronic characterizations verified that the Pt-modified SBTO NSs have broadened absorption of visible light; produce more long-lived charge carriers. The photocatalytic hydrogen production can reach 11700 μmol g−1 under continuous illumination for 3 h from the sample containing 6 wt% Pt, showing a much higher hydrogen evolution rate than other ferroelectric materials under similar reaction systems. Our work provides a valuable and feasible solution to produce hydrogen from water.
This study investigates how variations in substrate temperatures and deposition rates during pulsed laser deposition on Nb-doped SrTiO3 substrates affect the crystallinity, and consequently, the ...ferroelectric and piezoelectric properties of SrBi2Ta2O9 (SBT) thin films. The SBT thin film developed at 850 °C with a deposition rate of 0.34 nm/pulse showed lower remanent polarization and piezoelectric coefficients, a result of its c-oriented crystallinity. In contrast, SBT thin films produced at 750 °C with deposition rates of 0.37 nm/pulse demonstrated enhanced ferroelectric and piezoelectric responses due to mixed a-oriented crystallinity. In particular, the SBT thin film, fabricated at 750 °C with a lower deposition rate of 0.04 nm/pulse, demonstrated the most enhanced ferroelectric and piezoelectric properties due to its highly refined a-oriented crystallinity. Our findings illuminate the relationship between the characteristics of the crystals and functional properties in SBT thin films, highlighting the integration of a-domains within c-domains as a key strategy for optimizing SBT film performance and opening avenues for designing specialized Bi-layered perovskite thin films.
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•Fabricated SBT thin films via PLD on Nb:STO substrates with varied conditions.•Crystal structure and surface morphology crucially affect ferroelectric and piezoelectric properties.•Optimal SBT film performance achieved through integration of a-domains within c-domains.
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•The B-N bonds were formed between SBBO and HA under BM.•93.17 % of OTC can be piezoelectric degradation by SBBO/HA in 60 min.•A mechanism of B-N bond enhancing polarized electric ...field was clarified.•The degradation pathway for OTC was proposed basing on LC-MS and Fukui index.•The toxicity of the degradation product and intermediates decreased.
Constructing a chemical bond between the catalysts’ interfaces can establish a fast electron diffusion path and improve interfacial charge transport, thus produce a high efficiency in the catalytic field. We innovatively incorporate the humic acid (HA) and SrBi2B2O7 (SBBO) to degrade oxytetracycline (OTC) under ball milling (BM), the degradation efficiency of OTC for SBBO/HA under BM is 93.17 % and its pseudo-first-order kinetic constant is 0.0434 min−1, being 1.41 times than the sum of rate constant for HA (0.00826 min−1) and SBBO (0.0225 min−1), and 5.26 times than that for BaTiO3 (0.00825 min−1), illustrating their outstanding synthetic effect of SBBO and HA on piezoelectric degradation of OTC. The mechanism of enhanced piezoelectric activity was attributed to the B-N bond which enhances the local polarized electric field improving electron transfer and contributes to the generation of •O2– and •OH. The possible degradation pathways involving bonds cleavage, ring-opening, and dehydroxylation process were proposed based on LC-MS and Fukui index calculation. The toxicity of intermediates generated during the piezoelectric catalysis was predicted and investigated by T.E.S.T. software and mung bean growth. This study provides a new technology of enhancing piezoelectric catalytic activity by combining HA, SBBO and BM and clarifies the mechanism in detail.
The electron transfer between Fe2+ and Fe3+ was utilized in piezoelectric catalytic splitting seawater H2 evolution, which significantly improved the piezoelectric-catalyzed hydrogen production rate ...of the material, and is useful for future catalytic hydrogen production work.
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•SrBi4Ti4O15@FeS2 heterojunctions were prepared by electrostatic adsorption.•SrBi4Ti4O15@FeS2′s piezocatalytic hydrogen production in seawater can reach a high efficiency of up to 31 mmol g-1h−1.•SrBi4Ti4O15@FeS2 still maintains a high hydrogen evolution rate even in seawater with three times the salinity.•The electron cycling system of Fe2+ and Fe3+ is the key to enhance the surface activity while maintaining a strong redox capacity.
Piezoelectric catalytic seawater hydrogen production is one of the most crucial and potential hydrogen production strategies. However, the low surface activity and the high carrier recombination rate limit the further improvement of catalytic efficiency. To solve this problem, we prepared SrBi4Ti4O15 (SBTO) and FeS2 (FS) heterojunctions, which can effectively utilize the valence state transformation cycle between Fe2+ and Fe3+ to improve the surface activity and maintain carrier separation. This mechanism of Fe2+ and Fe3+ conversion is similar to the well-known Fenton reaction. It was confirmed by electrochemical measurements that with the help of FeS2, SBTO possessed a stronger piezoelectric current response and faster carrier transfer rate. Piezoelectric catalytic seawater splitting H2 evolution rate of SBTO-25 %FeS2 could reach 31 mmol g-1h−1, which is higher than that of other piezoelectric materials in similar conditions. Our findings provide valuable insights for further improving the efficiency of seawater hydrogen production efficiency.
We investigated the ferroelectric, piezoelectric, and domain wall current properties affected by the distribution of a-oriented domains and c-oriented domains in flexible SrBi2Ta2O9 (SBT) thin films ...on flexible Pt/mica substrates. On the flexible Pt/mica substrates, the SBT thin films with a mixed crystallinity of a-oriented and c-oriented crystallinities exhibited the domain structures mixed with a-oriented domains and c-oriented domains. The SBT thin films with excellent a-oriented crystallinity showed improved ferroelectric and piezoelectric properties due to the polar axis perpendicular to the c-axis. In particular, 90o domain walls composed of a-domain and c-domain have larger domain wall currents than 180o domain walls composed of c-domains, which increases the leakage current of the SBT thin films.
•Flexible polycrystalline SrBi2Ta2O9 thin films on Pt/mica substrates.•Ferroelectric domain structures with rectangular a-domains and elongated c-domains.•Enhanced ferroelectric and piezoelectric properties with c-domain distribution.•Leakage current characteristics improved by increasing distribution of a-domains.•Domain wall currents of 90o domain walls and 180o domain walls.
Fast recombination of photogenerated charge carriers in bulk remains the major obstacle for photocatalysis nowadays. Developing ferroelectrics directly as photoactive semiconducting catalysts may be ...promising in view of the strong ferroelectric polarization that induces the anisotropic charge separation. Here, we report a ferroelectric layered perovskite SrBi4Ti4O15 as a robust photocatalyst for efficient CO2 reduction. In the absence of co-catalysts and sacrificial agents, the annealed SrBi4Ti4O15 nanosheets with the strongest ferroelectricity cast a prominent photocatalytic CO2 reduction activity for CH4 evolution with a rate of 19.8 μmol h−1 g−1 in the gas-solid reaction system, achieving an apparent quantum yield (AQY) of 1.33% at 365 nm, outperforming most of the reported photocatalysts. The ferroelectric hysteresis loop, piezoresponse force microscopy (PFM) and ns-level time-resolved fluorescence spectra uncover that the outstanding CO2 photoreduction activity of SrBi4Ti4O15 mainly stems from the strong ferroelectric spontaneous polarization along 100 direction, which allows efficient bulk charge separation along opposite direction. DFT calculations also disclose that both electrons and holes show the smallest effective masses along a axis, verifying the high mobility of charge carriers facilitated by ferroelectric polarization. This study suggests that the traditionally semiconducting ferroelectric materials that have long been studied as ferro/piezoelectric ceramics now may be powerfully applied in the photocatalytic field to deal with the growing energy crisis.
A ferroelectric layered perovskite semiconductor SrBi4Ti4O15 was developed as an efficient photocatalyst for CO2 reduction. The outstanding photocatalytic activity of SrBi4Ti4O15 is stemmed from the strong ferroelectric spontaneous polarization and excellent electronic structure, favoring efficient bulk charge separation. Display omitted
•Nanostructured SrBi4Ti4O15 ferroelectric with large ferroelectricity was synthesized.•It shows outstanding photocatalytic CO2 reduction performance in gas phase.•The CH4 generation rate reaches 19.8 umol h−1 g−1 with a AQE of 1.33% at 365 nm.•Relationship between ferroelectricity and photocatalysis activity was clarified.
