Recycling of supported Au catalysts is challenging because of aggregation or loss of Au. Here, we report a strategy for introducing ZIF-8 into traditional Au/Al2O3 surface. The introduction of ZIF-8 can not only provide higher selectivity for the reaction products, but also prevent the loss or aggregation of the Au catalyst. From a series of characterizations, it can be seen that the ZIF-8 decorated Au/Al2O3 hybrid material Au@ZA (Z refers to ZIF-8, A refers to Al2O3) was successfully prepared. Au nanoparticles have better dispersion on the composite carrier, and the particle size is smaller. In the hydrogenation reaction of cinnamaldehyde (CAL), the Au@ZA composite catalyst has both the high chemical stability and the high selectivity of cinnamyl alcohol (COL) due to the micropore size effect of ZIF-8. The Au@ZA catalyst has similar to 85 % COL selectivity when the CAL conversion is close to 100 %. And after 8 times of repeated use, the conversion of CAL and the selectivity of COL did not decrease significantly. It should be noted that just when a small amount of ZIF-8 is present, the synergistic catalytic effect mentioned above can be produced.

Highly crystalline ZSM-23 zeolite, exhibiting a distinctive dumbbell morphology, was synthesized via a hydrothermal method. Bifunctional catalysts, comprising single metals (Pt or Au) and bimetals (Pt-Au), were successfully prepared by using a positional precipitation method. The hydroisomerization of hexadecane served as a model reaction to assess the catalytic performance arising from the synergistic effects of bimetallic active sites. In comparison to single-metal catalysts, 0.3Au0.7Pt/ZSM-23 demonstrated increased n-C-16 conversion, while 0.5Au0.5Pt/ZSM-23 exhibited enhanced i-C-16 selectivity, achieving the highest i-C-16 yield. The bimetallic catalyst not only finely tuned the metal site activity through bimetallic synergy but also achieved a superior balance between metal and acid catalysis, resulting in improved catalytic performance in the n-C-16 hydroisomerization. The Pt-Au bimetallic catalyst approached the ideal requirements for a hydroisomerization catalyst, achieving a harmonious balance of metal and acid catalysis.

Photoelectrocatalysis (PEC) technology has attracted broad interest due to its great application potential in pollutant removal and energy production. However, the high recombination of photogenerated electron-hole pairs, low utilization efficiency of solar energy, and limited reaction area are still the main obstacles that limit the practical applications of PEC. Carbon-based materials with unique and excellent properties are widely coupled with semiconductors to prepare composite photoelectrocatalysts to address the above problems. Carbon-based materials can serve as supporting materials, conductive substrates, electron transfer media, photosensitizers, and stabilizers to greatly improve the photoelectrocatalytic performance of semiconductors. Meanwhile, carbon-based materials can exert semiconductor properties to generate electron-hole pairs or construct heterojunctions with semiconductors to efficiently promote charge separation. In this review, a comprehensive summary is given to introduce synthetic methods and improvement strategies of carbon-based material/semiconductor composite photoelectrocatalysts, as well as their latest applications in the removal of organic pollutants. Especially, the roles of carbon-based materials in the PEC process are highlighted. Finally, current challenges and prospects are put forward. We do hope that this article can outline the recent advances and provide new insights for the future development of carbon-based semiconductor photoelectrocatalysts applied in water treatment.

Clarifying reactive oxygen species (ROS) variation in the presence of co-existing anions is significant for understanding the catalytic effect of magnetite (Fe3O4)-induced advanced oxidation processes (AOPs) in natural environment, yet this remains controversial. Herein, we compare the specific impacts of NO3-, SO42-, and Cl- on ROS (•OH, SO4•-, O2•-, and 1O2) exposure concentration in H2O2 and peroxydisulfate (PDS) systems catalyzed by Fe3O4, as well as how these variations affect the catalytic efficiency by developing kinetic model. In both two systems, NO3- demonstrates no discernible effect on ROS, whereas SO42- inhibits the exposure of all ROS and thus micropollutants degradation. Through theoretical calculation, it is proposed that SO42- primarily exerts its influence through affecting the electronic structure over catalyst surface. Regarding Cl-, it affects ROS exposure mainly by reacting with ROS. It shows inhibitory effect on 1O2 in both systems, but its suppressive impact on •OH is markedly more pronounced in H2O2 system compared to PDS system, which may be related to its rapid reactivity with SO4•-. Besides, the chlorine radicals (mainly ClO•) generated through the reaction of Cl- may exert a selective influence on micropollutants degradation. This study can help to re-understand the influence behavior of co-existing anions during AOPs.

Tetracycline (TC) antibiotics have been widely used over the past decades, and their massive discharge led to serious water pollution. Photo-Fenton process has gained ever-increasing attention for its excellent oxidizing ability and friendly solar energy utilization ability in TC polluted water treatment. This work introduced coordinative Fe into oxygen-enriched graphite carbon nitride (OCN) to form FeOCN composites for efficient photo-Fenton process. Hemin was chosen as the source to provide the source of coordinative Fe-Nx groups. The degradation efficiency of TC reached 82.1 % within 40 min of irradiation, and remained 76.9 % after five runs of reaction. The degradation intermediates of TC were detected and the possible degradation pathways were gained. It was found that h(+), (OH)-O-center dot, and O-center dot(2) played major roles in TC degradation. Notably, the photo-Fenton performance of FeOCN was stable in highly saline water or strong acid/base environment (pH 3.0-9.0). Besides, H2O2 can be generated in-situ in this photo-Fenton process, which is favorable for practical application. It can be anticipated that the coordinative FeOCN composites will promote the application of photo-Fenton oxidation process in TC polluted water treatment.

Converting carbon dioxide (CO2) into fuel and high-value-added chemicals is considered a green and effective way to solve global energy and environmental problems. Covalent triazine frameworks (CTFs) are extensively utilized as an emerging catalyst for photo/electrocatalytic CO2 reduction reaction (CO2RR) recently recognized for their distinctive qualities, including excellent thermal and chemical stability, π-conjugated structure, rich nitrogen content, and a strong affinity for CO2, etc. Nevertheless, single-component CTFs have the problems of accelerated recombination of photoexcited electron-hole pairs and restricted conductivity, which limit their application for photo/electrocatalytic CO2RR. Therefore, emphasis will then summarize the strategies for enhancing the photocatalytic and electrocatalytic efficiency of CTFs for CO2RR in this paper, including atom doping, constructing a heterojunction structure, etc. This review first illustrates the synthesis strategies of CTFs and the advantages of CTFs in the field of photo/electrocatalytic CO2RR. Subsequently, the mechanism of CTF-based materials in photo/electrocatalytic CO2RR is described. Lastly, the challenges and future prospects of CTFs in photo/electrocatalytic CO2RR are addressed, which offers a fresh perspective for the future development of CTFs in photo/electrocatalytic CO2RR.

Due to the contradiction between superior reaction kinetics and imperfect reproducibility of nanoscale zero-valent iron (nZVI) in persulfate oxidation systems, how to improve the reusability of nZVI while highly guaranteeing efficiency is an important but challenging matter. Hence, we took a hydrothermal-assisted carbon reduction to synthesize nZVI encapsulated with Bi being loaded on pomelo peel biochar (nZVI@Bi0/PPBC), and the results indicated that the presence of Bi could improve the reproducibility of nZVI and facilitate the removal of acetaminophen (ACE) in the persulfate (PDS) system. The degradation rate constant of the nZVI@Bi0/PPBC800 composite for ACE was approximately 1.5 times higher than that of the nZVI/PPBC800. nZVI exhibited synergistic effects with Bi on PDS activation through electron transfer. Interestingly, the Bi(0) became increasingly pure as the pyrolysis temperature increased, and the catalytic performance of ZVI@Bi0/PPBC became better. In addition,electron spin resonance and quenching experiments revealed that 1O2 and O2·− were the predominant reactive oxygen species in nZVI@Bi0/PPBC/PDS system.The nZVI@Bi0/PPBC/PDS system showed excellent oxidation ability across a broad pH range (3.0–9.0) and resisted interference from certain anions. This work reveals the possible role of Bi(0) in nZVI based PDS system, and provides an idea for the protection of nZVI.

In this paper, nickel (Ni)-tungsten (W) bimetallic carbide nanoparticles with different W : Ni ratios were prepared, and the catalytic deoxidation and hydrodeoxidation activities of the carbides were significantly improved by the modification and synergistic effect of the newly added second metal on the monometallic carbides. Pure phase Ni6W6C and W2C/Ni6W6C composites with different Ni contents were synthesized via organic and inorganic hybrid method. The structure and morphology of bimetallic carbides were characterized by XRD, XPS, BET, TEM, and SEM, and the Hydrodeoxygenation activity of bimetallic carbides was detected by hydrodeoxidationb reaction of benzofuran. Results showed that W2C and Ni–W bimetallic carbides had synergistic effects at certain W/Ni ratio. Even the formation of a small amount of Ni–W bimetallic carbides can significantly improve the catalytic activity. When the atomic ratio of W:Ni was 6 (the mass fraction of nickel is only 5

Currently, the strategy of metal loading is expected to promote the nonradical catalytic activity of transition metal spinel oxide catalysts in peroxymonosulfate (PMS) systems, but the connection between the mechanism of degradation performance improvement and metal-support interaction (MSI) remains unclear. Herein, a novel CoFe2O4 loaded sepiolite composite (10-CFS) was prepared for PMS activation to degrade ciprofloxacin (CIP). 10-CFS exhibited outstanding PMS activation ability, and 98.7% of CIP was degraded within 30 min, which was significantly higher than that of the physical mixture of sepiolite and CoFe2O4 (59.8%). A series of experiments demonstrated that the presence of Co(iv) 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 O caused the better degradation performance of 10-CFS. Notably, theoretical calculations signified that MSI not only promoted the coupled electron-proton transfer (CEPT) process and thus changed the formation pathway of Co(iv)O, but also facilitated PMS adsorption on 10-CFS and lowered the energy barrier for Co(iv)O generation. In summary, this study illustrates deeply the mechanism of catalytic performance improvement after metal loading by focusing on the MSI and bridges the gap in understanding the MSI and degradation performance. 10-CFS exhibited outstanding PMS activation ability, 98.7% of CIP was degraded within 30 min. The result demonstrated that the presence of Co(iv)O caused the better degradation performance of 10-CFS.

The electrochemical reduction of nitrate to ammonia represents a potential approach for the valorization of waste, offering the dual benefit of mitigating various environmental concerns and concurrently yielding the valuable product of ammonia. However, on the way to its further application, the lacking of low-cost and efficient electrocatalysts under low nitrate concentrations is still one pressing issue because of the intense hydrogen evolution reaction (HER) competition and many by-products. Herein, metal - organic frameworks (MOF) derived low-cost Cu-Co 3 O 4 /NF exhibits excellent electrocatalytic activity in the low nitrate concentrations (2 mmol/L), attaining the ammonia yield rate of 0.076 mmol h -1 cm -2 and 92.4 % Faradic efficiency at -0.53 V vs. RHE. The combined results of In -situ FTIR and theoretical calculation reveal the atomic hydrogen reduction pathway, decrease in free energy of intermediate reactions and inhibition of HER of Cu-Co 3 O 4 /NF. This work introduces one economical, efficient and simple strategy and further demonstrates the superior effect of MOF derivatives in fascinating low nitrate concentration reduction to ammonia.

Propylene, as an important chemical basic raw material, is in increasing demand year by year. Au/ZSM-5 as a bifunctional catalyst exhibits excellent catalytic performance and propylene selectivity in low-temperature catalytic cracking to propylene reaction. The smaller Au size (5.8-8.2 nm) is prepared through deposition precipitation, but the characteristics of support will also undergo partial changes at the same time. The support characteristics have been confirmed to have changed through a series of characterizations. The propylene yield could reach 42% at 410 oC when the value of CH/CM is 40. A proposed metal-acid synergistic catalysis mechanism for octane catalytic cracking to produce propylene is elucidated. The higher propylene yield is attributed to the synergy between acid sites and Au species. Our research results provide a reasonable and effective correlation between the metal-acid activity of bifunctional catalysts and catalytic activity in catalytic cracking reactions to produce propylene.

In this study, we synthesized Fe and Ti co-doped graphitic carbon nitride (FTCN) with high catalytic ability by a two-step calcination method. The photoelectrochemical results indicated that FTCN possessed a reduced bandgap and promoted photocarrier transfer efficiency, which enables FTCN excellent performance on oxytetracycline (OTC) degradation (90 % within 10 min). The main reactive oxygen species and the intermediates of OTC in the photo-Fenton process were obtained. Experimental data and density functional theory (DFT) were combined to explore the mechanism in depth. Interestingly, it was found that Fe and Ti respectively act as the main activation centers of H2O2 and O2, while few oxygen-containing metal active sites participate in the activation process. The synergistic effect of bimetallic doping plays a significant role in enhancing the photoFenton catalytic performance. Hopefully, a new approach to design highly efficient multifunctional catalysts or dual single-atom catalysts can be developed.

Photocatalysis is currently a hot research field, which provides promising processes to produce green energy sources and other useful products, thus eventually benefiting carbon emission reduction and leading to a low-carbon future. The development and application of stable and efficient photocatalytic materials is one of the main technical bottlenecks in the field of photocatalysis. Perovskite has excellent performance in the fields of photocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), carbon dioxide reduction reaction (CO2RR), organic synthesis and pollutant degradation due to its unique structure, flexibility and resulting excellent photoelectric and catalytic properties. The stability problems caused by perovskite's susceptibility to environmental influences hinder its further application in the field of photocatalysis. Therefore, this paper innovatively summarizes and analyzes the existing methods and strategies to improve the stability of perovskite in the field of photocatalysis. Specifically, (i) component engineering, (ii) morphological control, (iii) hybridization and encapsulation are thought to improve the stability of perovskites while improving photocatalytic efficiency. Finally, the challenges and prospects of perovskite photocatalysts are discussed, which provides constructive thinking for the potential application of perovskite photocatalysts.

Single-atom catalysts (SACs) for photocatalytic hydrogen peroxide (H2 O2 ) generation are researched but it is still challenging to obtain high H2 O2 yields. Herein, graphite carbon nitride (FeSA /CN) confined single Fe atoms with N/O coordination is prepared, and FeSA /CN shows high H2 O2 production via oxalic acid and O2 activation. Under visible light illumination, the concentration of H2 O2 generated by FeSA /CN can achieve 40.19 mM g-1 h-1 , which is 10.44 times higher than that of g-C3 N4 . The enhanced H2 O2 generation can be attributed to the formation of metal-organic complexes and rapid electron transfer. Moreover, the O2 activation of photocatalysts is revealed by 3,3',5,5'-tetramethylbenzidine oxidation. The results display that the O2 activation capacity of FeSA /CN is higher than that of g-C3 N4 , which facilitates the formation of H2 O2 . Finally, density functional theory calculation demonstrates that O2 is chemically adsorbed on Fe atomic sites. The adsorption energy of O2 is enhanced from -0.555 to -1.497 eV, and the bond length of OO is extended from 1.235 to 1.292 Å. These results exhibit that the confinement of single Fe atoms can promote O2 adsorption and activation. Finally, the photocatalytic mechanism is elaborated, which provides a deep understanding for SACs-catalyzed H2 O2 generation.

As a rising branch of advanced oxidation processes, persulfate activation has attracted growing attention. Unlike catalysts that have been widely studied, the selection of persulfate is previously overlooked. In this study, the affecting factors of persulfates were studied. The effect of target pollutant properties on superior persulfate species (the species with a higher degradation efficiency) was investigated by multiwalled carbon nanotube (MWCNT)/persulfate catalytic systems. Innovatively, the EHOMO (or vertical ionization potential (VIP)) value of the target pollutant was proposed to be an index to judge the superior persulfate species, and the threshold is VIP= 6.397-6.674 eV, EHOMO= -8.035∼- 7.810 eV, respectively. To be specific, when the VIP of phenolic compounds is higher (or EHOMO of phenolic compounds is lower) than the threshold, the catalytic performance of peroxymonosulfate would be higher than that of peroxydisulfate. Moreover, the effects of coexisting cations on peroxydisulfate superior species were further investigated. It was illustrated that the hydrated cation radius of coexisting cations would influence the pollutant degradation efficiency under some circumstances. This study provides a new approach to improve the cost of persulfate activation systems and promotes the underlying downstream application of persulfate activation systems.

Single-atom catalysts (SACs) have been widely used in Fenton-like water treatment, but studies on the selective induction of H2O2 to produce singlet oxygen (O-1(2)) are rare. Herein, a carbon nitride supported high-loaded single-atom Cu-N-3 catalyst (Cu-CN, Cu load is 15.46 wt%) is prepared to activate H2O2 to selectively form O-1(2). Experimental and DFT calculation results reveal that the key factor for 1O2 production is the Cu-N-3 coordination structure. Specifically, Cu-N-3 coordination structure is conducive to decomposing H2O2 into center dot OOH/center dot O-2(-). Besides, the density of Cu-N-3 sites is another key factor, high Cu-N-3 site density is conducive to the rapid conversion of center dot OOH/center dot O-2(-) to O-1(2). Benefitting from the dominant role of O-1(2), the Fenton-like degradation performance of Cu-CN/H2O2 system is not disturbed under high salinity conditions, and the performance is significantly enhanced at high pH. This work represents an important reference in understanding SACs for activated H2O2 to generate O-1(2).

Future renewable energy supply and green, sustainable environmental development rely on various types of catalytic reactions. Copper single-atom catalysts (Cu SACs) are attractive due to their distinctive electronic structure (3d orbitals are not filled with valence electrons), high atomic utilization, and excellent catalytic performance and selectivity. Despite numerous optimization studies are conducted on Cu SACs in terms of energy conversion and environmental purification, the coupling among Cu atoms-support interactions, active sites, and catalytic performance remains unclear, and a systematic review of Cu SACs is lacking. To this end, this work summarizes the recent advances of Cu SACs. The synthesis strategies of Cu SACs, metal-support interactions between Cu single atoms and different supports, modification methods including modification for carriers, coordination environment regulating, site distance effect utilizing, and dual metal active center catalysts constructing, as well as their applications in energy conversion and environmental purification are emphatically introduced. Finally, the opportunities and challenges for the future Cu SACs development are discussed. This review aims to provide insight into Cu SACs and a reference for their optimal design and wide application.

As one of the tactics to produce reactive oxygen radicals, the Fenton-like process has been widely developed to solve the increasingly severe problem of environmental pollution. However, establishing advanced mediators with sufficient stability and activity for practical application is still a long-term objective. Herein, we proposed a facile strategy through polymeric carbon nitride (pCN) in-situ growth single cobalt atom for efficient degradation of antibiotics by peroxymonosulfate (PMS) activation. Xray absorption spectroscopy and high-angle annular dark field-scanning transmission electron microscopy prove the single cobalt atoms are successfully anchored on pCN. Moreover, extended X-ray absorption fine structure analysis shows that the embedded cobalt atoms are constructed by covalently forming the Co-N bond and Co-O bond, which endow the single-atom cobalt catalyst with high stability. Experiment results indicate that the prepared single-atom cobalt catalyst can be used for efficient PMS activation catalytic degradation of tetracycline with a high degradation rate of 98.7 % in 60 min. And the CoN/O sites with single cobalt atoms serve as the active site for generating active radical species (singlet oxygen) from PMS activation. This work may expand the strategy for constructing single-atom catalysts and extend its application for the advanced oxidation process. (C) 2022 Published by Elsevier Inc.

The photothermal process has attracted considerable attention in water treatment due to its advantages of low energy consumption and high efficiency. In this respect, photothermal materials play a crucial role in the photothermal process. Particularly, carbonaceous materials have emerged as promising candidates for this process because of exceptional photothermal performance. While previous research on carbonaceous materials has primarily focused on photothermal evaporation and sterilization, there is now a growing interest in exploring the potential of photothermal effect-assisted advanced oxidation processes (AOPs). However, the underlying mechanism of the photothermal effect assisted by carbonaceous materials remains unclear. This review aims to provide a comprehensive review of the photothermal process of carbonaceous materials in water treatment. It begins by introducing the photothermal properties of carbonaceous materials, followed by a discussion on strategies for enhancing these properties. Then, the application of carbonaceous materials-based photothermal process for water treatment is summarized. This includes both direct photothermal processes such as photothermal evaporation and sterilization, as well as indirect photothermal processes that assisted AOPs. Meanwhile, various mechanisms assisted by the photothermal effect are summarized. Finally, the challenges and opportunities of using carbonaceous materials-based photothermal processes for water treatment are proposed.

Heterogeneous Fenton-like process based on H2O2 activation has been widely tested for water purification, but its application still faces some challenges such as the use of high doses of chemicals (including catalysts and H2O2). Herein, a facile co-precipitation method was utilized for small-scale production (∼50 g) of oxygen vacancies (OVs)-containing Fe3O4 (Vo-Fe3O4) for H2O2 activation. Experimental and theoretical results collaboratively verified that H2O2 adsorbed on the Fe site of Fe3O4 tended to lose electrons and generate O2•-. While the localized electron from OVs of Vo-Fe3O4 could assist in donating electrons to H2O2 adsorbed on OVs sites, this allowed more H2O2 to be activated to •OH, which was 3.5 folds higher than Fe3O4/H2O2 system. Moreover, the OVs sites promoted dissolved oxygen activation and decreased the quenching of O2•- by Fe(III), thus promoting the generation of 1O2. Consequently, the fabricated Vo-Fe3O4 achieved much higher oxytetracycline (OTC) degradation rate (91.6%) than Fe3O4 (35.4%) at a low catalyst (50 mg/L) and H2O2 dosage (2 mmol/L). Importantly, further integration of Vo-Fe3O4 into fixed-bed Fenton-like reactor could effectively eliminate OTC (>80%) and chemical oxygen demand (COD) (21.3%∼50%) within the running period. This study provides promising strategies for enhancing the H2O2 utilization of Fe mineral.