Insight into the effect of OH modification on the piezo-photocatalytic hydrogen production activity of SrTiO3

Scalable synthesis of Bi2O2S nanoplates with large piezoelectric potential induced by a built-in electric field in a [Bi2O2]2+ layer for the degradation of organic contaminants

2D piezoelectric catalysts with strong piezoresponse and high piezoelectric potential have valuable applications in catalytic degradation of organic pollutants and antibiotics, but the development of novel nanomaterials with powerful piezopotential still remains a serious challenge. Bismuth oxysulfide (Bi2O2S) nanosheets possessing large piezoelectric potentials were prepared using a low-heating solid-state chemical reaction and used for the first time for piezoelectric catalysis in this work. Moreover, Bi2O2S nanosheets can degrade pollutants universally, and the degradation efficiencies of methyl blue and rhodamine B are as high as 97.7% and 92.9% within 60 min under ultrasonication, respectively, which is superior to most piezoelectric materials reported in the literature.

Twin Boundaries-Induced Centrosymmetric Breaking of Hollow CaTiO3 Nanocuboids for Piezocatalytic Hydrogen Evolution

Piezocatalysis, a transformative mechanochemical energy conversion technique, has received considerable attention over the past decade for its role in processes such as hydrogen evolution from water. Despite notable progress in the field, challenges remain, particularly in the areas of limited piezocatalysis efficiency and limited availability of materials requiring a non-centrosymmetric structure. Here, a pioneering contribution is presented by elucidating the piezocatalytic properties of hollow CaTiO3 nanocuboids, a centrosymmetric material with a nominally nonpolar state. Remarkably, CaTiO3 nanocuboids exhibit an impressive hydrogen production rate of 3.44 mmol g-1 h-1 under ultrasonic vibrations, surpassing the performance of the well-established piezocatalyst BaTiO3 (2.23 mmol g-1 h-1). In contrast, commercial CaTiO3 nanoparticles do not exhibit piezocatalytic performance. The exceptional performance of hollow CaTiO3 nanocuboids is attributed to the abundance presence of twin boundaries on the {110} facet within its crystal structure, which can impart significant polarization strength to CaTiO3. Extending the investigation to other centrosymmetric materials, such as SrZrO3 and BaZrO3, the experimental results also demonstrate their commendable properties for piezocatalytic hydrogen production from water. This research underscores the significant potential of centrosymmetric materials in piezocatalysis.

The photocatalytic wastewater hydrogen production process with superior performance to the overall water splitting

The utilization of a cost-free sacrificial agent is a novel approach to significantly enhance the efficiency of photocatalytic hydrogen (H2) production by water splitting. Wastewater contains various organic pollutants, which have the potential to be used as hole sacrificial agents to promote H2 production. Our studies on different pollutants reveals that not all pollutants can effectively promote H2 production. However, when using the same pollutants, not all photocatalysts achieved a higher H2 evolution rate than pure water. Only when the primary oxidizing active species of the photocatalyst are •OH radicals, which are generated by photogenerated holes, and when the pollutants are easily attacked and degraded by •OH radicals, can the production of H2 be effectively promoted. It is noteworthy that the porous brookite TiO2 photocatalyst exhibits a significantly higher H2 evolution rate in Reactive Red X-3B and Congo Red, reaching as high as 26.46 mmol⋅g-1⋅h-1 and 32.85 mmol⋅g-1 ⋅h-1, respectively, which is 2-3 times greater than that observed in pure water and is 10 times greater than most reported studies. The great significance of this work lies in the potential for efficient H2 production through the utilization of wastewater.

Recent advances of piezo-catalysis and photocatalysis for efficient environmental remediation

The efficient degradation of organic pollutants in diverse environmental matrices can be achieved through the synergistic application of piezo-catalysis and photocatalysis. The focus of this study is on understanding the fundamental principles and mechanisms that govern the collaborative action of piezoelectric and photocatalytic materials. Piezoelectric nanomaterials, under mechanical stress, generate piezo-potential, which, when coupled with photocatalysts, enhances the generation and separation of charge carriers. The resulting cascade of redox reactions promotes the degradation of a wide spectrum of organic pollutants. The comprehensive investigation involves a variety of experimental techniques, including advanced spectroscopy and microscopy, to elucidate the intricate interplay between mechanical and photoinduced processes. The influence of key parameters, such as material composition, morphology, and external stimuli on the catalytic performance, is systematically explored. This study contributes to the increasing knowledge of environmental remediation and lays the foundation for the development of advanced technologies using piezo and photocatalysis for sustainable pollutant removal.

Elucidating Structural Stability, Bandgap, and Photocatalytic Hydrogen Evolution of (H2O/DMF)@HKUST-1 Host-Guest Systems

The H2O@HKUST-1 and DMF@HKUST-1 systems were experimental and computationally assessed, employing XRD/TGA/FT-IR/DFT-calculations, evidencing that H2O or DMF coordinated to Cu, modulating HKUST-1 photocatalytic properties. DMF@HKUST-1 has narrower bandgap promoting higher-crystallinity and light-harvesting. H2O@HKUST-1 showed smaller particle sizing and sharp morphology. Theoretical models, (H2O)1@HKUST-1 and (DMF)1@HKUST-1, containing one coordinated molecule, elucidated bandgap modulation associated with infiltration. H2O@HKUST-1/DMF@HKUST-1 presented bandgaps [eV] of 3.6/3.4, by Tauc plots, and 3.55/3.26, by theoretical calculations, narrowing bandgap, compared with non-solvated HKUST-1(HKUST-1NS). Both composites raised the valence band (VB) and lowered the conduction band (CB), but DMF@HKUST-1 most raised VB. Topological analysis revealed that guests i) with higher electronic density, raised VB, and ii) induced π-backbonding, lowering CB. DMF@HKUST-1 presented a higher photocatalytic hydrogen evolution (μmol), 26.45, in the first 30 min of the reaction, nevertheless, H2O@HKUST-1 presented a competitive activity, of 17.32. In large periods, H2O@HKUST-1/DMF@HKUST-1 showed practically the same hydrogen evolution, 45.50/49.03.

A comprehensive review on the application of semiconducting materials in the degradation of effluents and water splitting

In this comprehensive review article, we delve into the critical intersection of environmental science and materials science. The introduction sets the stage by emphasizing the global water shortage crisis and the dire consequences of untreated effluents on ecosystems and human health. As we progress into the second section, we embark on an intricate exploration of piezoelectric and photocatalytic principles, illuminating their significance in wastewater treatment and sustainable energy production. The heart of our review is dedicated to a detailed analysis of the detrimental impacts of effluents on human health, underscoring the urgency of effective treatment methods. We dissected three key materials in the realm of piezo-photocatalysis: ZnO-based materials, BaTiO3-based materials, and bismuth-doped materials. Each material is scrutinized for its unique properties and applications in the removal of pollutants from wastewater, offering a comprehensive understanding of their potential to address this critical issue. Furthermore, our exploration extends to the realm of hydrogen production, where we discuss various types of hydrogen and the role of piezo-photocatalysis in generating clean and sustainable hydrogen. By illuminating the synergistic potential of these advanced materials and technologies, we pave the way for innovative solutions to the pressing challenges of water pollution and renewable energy production. This review article not only serves as a valuable resource for researchers and scholars in the fields of material science and environmental engineering but also underscores the pivotal role of interdisciplinary approaches in addressing complex global issues.

Defective ReS2 Triggers High Intrinsic Piezoelectricity for Piezo-Photocatalytic Efficient Sterilization

Rhenium disulfide (ReS2) is a promising piezoelectric catalyst due to its excellent electron transfer ability and abundant unsaturated sites. The 1T' phase structure leads to the evolution of ReS2 into a centrosymmetric spatial structure, which restricts its application in piezoelectric catalysis. Herein, we propose a controllable defect engineering strategy to trigger the piezoelectric response of ReS2. The introduction of vacancy defects disrupts the initial centrosymmetric structure, which breaks the piezoelectric polarization bond and generates piezoelectric properties. By using transmission electron microscopy, we characterized it at the atomic scale and determined that vacancy defects contribute to an excellent piezoelectric property through first-principles calculations. Notably, the piezoelectric coefficient of the catalyst with 40 s-etching (ReS2@C-40) is 23.07 pm/V, an order of magnitude greater than other transition metal dichalcogenides. It demonstrated the feasibility of optimizing piezoelectric properties by increasing the conformational asymmetry. Based on its remarkable piezoelectric activity, ReS2@C-40 exhibits highly efficient piezo-photocatalytic synergistic sterilization performance with 99.99% eradication of Escherichia coli and 96.67% of Staphylococcus aureus within 30 min. This pioneering research on the coupling effect of ReS2 in piezoelectric catalysis and photocatalysis provides ideas for the development of piezo-photocatalysts and efficient water purification technologies.

Rational design of CdS/BiOCl S-scheme heterojunction for effective boosting piezocatalytic H2 evolution and pollutants degradation performances

Piezocatalysis as an emerging technology is broadly applied in hydrogen evolution and organic pollutants degradation aspects. However, the dissatisfactory piezocatalytic activity is a severe bottleneck for its practical applications. In this work, CdS/BiOCl S-scheme heterojunction piezocatalysts were constructed and explored the performances of piezocatalytic hydrogen (H₂) evolution and organic pollutants degradation (methylene orange, rhodamine B and tetracycline hydrochloride) under strain by ultrasonic vibration. Interestingly, CdS/BiOCl presents a volcano-type relationship between catalytic activity and CdS contents, namely firstly increases and then decreases with the increase of CdS content. Optimal 20 % CdS/BiOCl endows superior piezocatalytic H₂ generation rate of 1048.2 μmol g^-1h^-1 in methanol solution, which is 2.3 and 3.4 times higher than that of pure BiOCl and CdS, respectively. This value is also much higher than the recently reported Bi-based and most of other typical piezocatalysts. Meanwhile, 5 % CdS/BiOCl delivers the highest reaction kinetics rate constant and degradation rate toward various pollutants compared with other catalysts, which also exceeds that of the previously numerous results. Improved catalytic capacity of CdS/BiOCl is mainly ascribed to the construction of S-scheme heterojunction for enhancing the redox capacity as well as inducing more effective charge carriers separation and transfer. Moreover, S-scheme charge transfer mechanism is demonstrated via electron paramagnetic resonance and Quasi-In-situ X-ray photoelectron spectroscopy measurements. Eventually, a novel piezocatalytic mechanism of CdS/BiOCl S-scheme heterojunction has been proposed. This research develops a novel pathway for designing highly efficient piezocatalysts and provides a deeper understanding in construction of Bi-based S-scheme heterojunction catalysts for energy conservation and wastewater disposal applications.

Piezoelectric materials and techniques for environmental pollution remediation

With the rapid development of industrialization and agriculture, a series of critical imminent environmental problems and water pollution have caught wide attention from the public and society. Piezoelectric catalysis technology with piezoelectric materials is a green and environmental method that can efficiently improve the separation of electron-hole pairs, then generating the active substances such as OH, H₂O₂ and O₂^-, which can degrade water pollutants. Therefore, we firstly surveyed the piezoelectric catalysis in piezoelectric materials and systematically concluded and emphasized the relationship between piezoelectric materials and the piezoelectric catalytic mechanism, the goal to elucidate the effect of polarization on piezoelectric catalytic performance and enhance piezoelectric catalytic performance. Subsequently, the applications of piezoelectric materials in water treatment and environmental pollutant remediation were discussed including degradation of organic pollutants, removal of heavy mental ions, radionuclides, bacteria disinfection and water splitting for H₂ generation. Finally, the development prospects and future outlooks of piezoelectric catalysis were presented in detail.

Construction of an S-scheme TiOF2/HTiOF3 heterostructures with abundant OVs and OH groups: Performance, kinetics and mechanism insight

Developing efficient photocatalysts is of crucial significance for the development of photocatalysis techniques. In this work, an S-scheme alkaline-washed TiOF₂/HTiOF₃(OHTOF) heterostructures with abundant Oxygen vacancies (Ovs) and OH groups was successfully constructed and used to remedy antibiotic wastewater under simulated sunlight. The generation of HTiOF₃ was induced by g-C₃N₄ regulation. The results displayed that OHTOF15 composite possessed the best photocatalytic performance, which could degrade 94.2% tetracyclinehydrochloride (TCH) at a rate speed constant of 1.077 min^-1 in 2.5 h. The after-alkali-washing process increased the concentration of OH groups and Ovs defects, and greatly enlarged the surface area. The abundant Ovs and OH groups were conducive to the formation of free radicals' and the transport of charge carriers. Compared with the pristine TiOF₂, the absorption sidebands of OHTOF series were greatly red-shifted, which indicated that the increase of OH groups and the etching of the morphology of OHTOF further enhanced its visible-light harvesting ability. Furthermore, the metal cycle of the variable state of Ti⁴⁺/Ti³⁺ in OHTOF15 compensated for the charge balance and promoted the efficient separation of the carriers. Additionally, the apparent quantum efficiency (AQE) of the TCH photodegradation system based on Chemical Oxygen Demand (COD) removal efficiency was calculated to be 0.32%. It was confirmed that the electron transport path in TiOF₂/HTiOF₃ nanocomposites system followed the S-scheme type, which increased the charge carriers' separation rate and maintained a strong redox capacity. This work could provide some enlightenment for the construction of the semiconducting heterojunction and controllable surface defects engineering.

Fabrication of In-S-co-doped two-dimensional BiOCl coupling with surface hydroxylation toward simultaneously efficient charge separation and redox capability for photocatalytic water remediation

Tailoring energy band structure of bismuth oxychloride (BiOCl)-based photocatalysts by virtue of the metal and/or non-metal elements is one of the promising strategy to address environmental issues, especially plays a crucial role in water remediation. However, it still remains a great challenge to balance the light-harvesting and charge carriers separation. Herein, a feasible strategy was proposed for the simultaneous integration of energy-band modulation and surface hydroxylation to alleviate the as-mentioned contradiction and long-standing issues. By using a simple one-pot hydrothermal method, In-S-co-doped BiOCl photocatalyst coupling with surface hydroxylation (denoted as In/BOC-S-OH) was prepared by the simultaneous co-precipitation and ripening process and exhibited a good photocatalytic activity for removing tetracycline (TC) under visible light-irradiation than the counterparts of In-doped BiOCl (In/BOC), S-doped BiOCl (In/BOC-S) or surface -OH modification BiOCl (In/BOC-OH). Such satisfied photocatalytic efficiency benefits from the synergistic effect on the visible light capture, charge migration and separation associated with the introduction of intermediate energy levels and surface defect, respectively. Accompanying with the introduction of In and S hetero-atoms intercalation, both the potentials of valence and conduction bands were adjusted and the reduction of the bandgap could promote the capture of photons. Meanwhile, the powerful polarization effect associated with the non-uniform charge distribution could promote the special separation of carriers. More importantly, the surface defects induced by hydroxylation could act as traps for photogenerated electrons to stimulate the rapid separation of carriers, thereby causing the cleavage of antibiotics on the catalytic surface. This research offers a reliable strategy and promising scheme via effective solar energy conversion and charge carrier separation to advance photocatalytic wastewater remediation.

Non-radical-dominated catalytic degradation of methylene blue by magnetic CoMoO4/CoFe2O4 composite peroxymonosulfate activators

In this study, magnetic CoMoO₄/CoFe₂O₄ (CMO/CFO) nanospheres with a core-shell structure were synthesized via two-step hydrothermal methods. The obtained particles were employed as catalysts to activate peroxymonosulfate (PMS) and degrade methylene blue (MB). The physico-chemical characterizations of the synthesized CMO/CFO showed that the CMO shell contributed to the enhancement of redox conversion and the increase in the concentration of oxygen vacancies (OVs). By examining reactive oxygen species (ROS) in the CMO/CFO/PMS system, the MB degradation was dominated by a non-radical pathway, and ¹O₂ was identified as the most abundant ROS. Besides, the CMO/CFO exhibited faster reaction kinetics than the pristine CFO. Moreover, the magnetic properties guaranteed the recycling and reuse of CMO/CFO, and the removal rate of MB was maintained at ∼94% after continuous use five times. Both the tolerance to SO₄^2-and the wide pH range where the material is applicable make it a promising catalyst for dyeing wastewater treatment.

Recent Advancements in Photocatalysis Coupling by External Physical Fields

Photocatalysis is one of the most promising green technologies to utilize solar energy for clean energy achievement and environmental governance, such as artificial photosynthesis, water splitting, pollutants degradation, etc. Despite decades of research, the performance of photocatalysis still falls far short of the requirement of 5% solar energy conversion efficiency. Combining photocatalysis with the other physical fields has been proven to be an efficient way around this barrier which can improve the performance of photocatalysis remarkably. This review will focus on the recent advances in photocatalysis coupling by external physical fields, including Thermal-coupled photocatalysis (TCP), Mechanical-coupled photocatalysis (MCP), and Electromagnetism-coupled photocatalysis (ECP). In this paper, coupling mechanisms, materials, and applications of external physical fields are reviewed. Specifically, the promotive effect on photocatalytic activity by the external fields is highlighted. This review will provide a detailed and specific reference for photocatalysis coupling by external physical fields in a deep-going way.