Search Results (182)

Accelerated industrialization and surging energy demands have led to continuously rising atmospheric CO₂ concentrations. Developing sustainable methods to reduce atmospheric CO₂ levels is crucial for achieving carbon neutrality. Concurrently, the rapid development of new energy vehicles has driven a significant increase in demand for lithium-ion batteries (LIBs), which are now approaching an end-of-life peak. Efficient recycling of valuable metals from spent LIBs represents a critical challenge. This study employs conventional hydrometallurgical processing to recover valuable metals from spent LIBs. Subsequently, Ni-doped Co₃O₄ (Ni:Co₃O₄) supported on the natural mineral attapulgite (ATP) was synthesized via a sol–gel method. The incorporation of a small amount of Ni into the Co₃O₄ lattice generates oxygen vacancies, inducing a localized surface plasmon resonance (LSPR) effect, which significantly enhances charge carrier transport and separation efficiency. During the photocatalytic reduction of CO₂, the primary product CO generated by the Ni:Co₃O₄/ATP composite achieved a high production rate of 30.1 μmol·g⁻¹·h⁻¹. Furthermore, the composite maintains robust catalytic activity even after five consecutive reaction cycles. Full article

Over efficient photocatalysts, CO₂ photoreduction typically converts CO₂ into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu₂O-u/g-C₃N₄) has been fabricated to reduce CO₂. Graphitic carbon nitride (g-C₃N₄) was synthesized via thermal polymerization of urea at 550 °C, while pre-dispersed Cu₂O derived from urea pyrolysis (Cu₂O-u) was prepared by thermal reduction of urea and CuCl₂·2H₂O at 180 °C. The heterojunction Cu₂O-u/g-C₃N₄ was subsequently constructed through hydrothermal treatment at 180 °C. This heterojunction exhibited a bandgap of 2.10 eV, with dual optical absorption edges at 485 nm and above 800 nm, enabling efficient harvesting of solar light. Under 175 W mercury lamp irradiation, the heterojunction catalyzed liquid-phase CO₂ photoreduction to formic acid, acetic acid, and methanol. Its formic acid production activity surpassed that of pristine g-C₃N₄ by 3.14-fold and TiO₂ by 8.72-fold. Reaction media, hole scavengers, and reaction duration modulated product selectivity. In acetonitrile/isopropanol systems, formic acid and acetic acid production reached 579.4 and 582.8 μmol·h⁻¹·g_cat⁻¹. Conversely, in water/triethanolamine systems, methanol production reached 3061.6 μmol·h⁻¹·g_cat⁻¹, with 94.79% of the initial conversion retained after three cycles. Finally, this work ends with the conclusions of the CO₂ photocatalytic reduction to formic acid, acetic acid, and methanol, and recommends prospects for future research. Full article

The photocatalytic reduction of CO₂ into valuable hydrocarbons presents significant potential. In this research, a ZnO/ZnAl₂O₄ composite photocatalyst was synthesized using the hydrothermal method, resulting in a marked enhancement in CO yield—approximately three times greater than that achieved with pure ZnAl₂O₄ nanoparticles. The formation of a Z-scheme heterojunction between ZnO and ZnAl₂O₄ was observed, characterized by low interfacial charge transfer resistance, an abundance of reaction sites, and optimized charge transport pathways. Within this composite, ZnO contributes additional vacancies, thereby increasing active sites and enhancing the separation and migration of photogenerated carriers. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis indicates that ZnAl₂O₄ facilitates the formation of key intermediates, such as *COOH and HCO₃⁻, thus promoting the conversion of CO₂ to CO. This study offers valuable insights into the design of heterogeneous catalysts with diverse active components to enhance the performance of CO₂ photocatalytic reduction through synergistic effects. Full article

NiS nanoparticles were chemically deposited on the surface of g-C₃N₄, in situ, followed by high-temperature calcination to prepare x-NiS/g-C₃N₄ co-catalyst-based S-scheme heterojunction photocatalysts. Due to the intrinsic charge accumulation preference on specific crystal planes of g-C₃N₄, NiS nanoparticles selectively deposited on its surface and formed a strong interfacial contact, thereby constructing an S-scheme heterojunction with co-catalytic functionality. This structure effectively suppressesd the recombination of electron–hole pairs in the valence band, significantly enhancing the separation efficiency of photogenerated charge carriers, and thereby improving performance in photocatalytic CO₂ reduction. Compared with pure g-C₃N₄, the x-NiS/g-C₃N₄ photocatalysts exhibit superior CO₂ reduction activity. Among them, the sample with 1.0% NiS loading showed the best performance, achieving CO and CH₄ production rates of 27.34 μmol/g and 13.87 μmol/g, respectively, within 4 h. Full article

Photocatalytic CO₂ conversion is one of the ideal approaches to address both topics of solar energy shortage and carbon neutrality. Cobalt(II) centers coordinated with bipyridines have been designed and evaluated as catalysts for CO₂ conversion under light irradiation. Herein, we report a series of pyridine-based cobalt complexes with alkyl substituents as molecular photocatalysts, aiming to elucidate the effects of alkyl type and substitution position on catalytic performance through spectroscopic and electrochemical measurements. The substitution of the hydrogen at 4,4′-positions on the bipyridine ring with a methyl group, a tert-butyl group, and a nonyl group led to a decrease in the conversion rate of CO₂ by 13.2%, 29.6%, and 98%, respectively. The methyl substituents at the 5, 5′-positions of the bipyridine ring resulted in a 71.1% decrease in the CO₂ conversion rate. The usage of either 6, 6′-Me₂-2,2′-bipy, 2,4-bipy, or 3,3′-bipy resulted in no detectable activity for CO₂ conversion in the current system. Both photo- and electrochemical analyses have been employed to reveal the relationship between changing ligands and photocatalytic performance on the molecular scale. These results demonstrate that bulky ligands significantly hinder CO₂ reduction by cobalt complexes due to steric interference with coordination and active-site accessibility. This study demonstrates that the substituent effect of ligands on photocatalytic reactions for CO₂ conversion provides valuable insight into a deeper understanding of molecular catalysis. Full article

A rational design strategy for active sites on the catalyst surface can effectively enhance CO₂ reduction reaction (CO₂RR) selectivity. Transition metal atoms from the fourth (Sc–Ni) and fifth (Y–Mo, Ru–Pd) periods were doped onto the In₂S₂X (X = Se, Te) surface to control bimetallic active sites. The study showed that the d-band center’s position of the dopant atom significantly influences CO₂RR selectivity. Cations with positive d-band centers further from the Fermi level are more inclined towards CH₂O, while those with negative d-band centers closer to the Fermi level favor HCOOH; cations with d-band centers near the Fermi level exhibit a strong preference for CH₃OH. This study systematically elucidates the intrinsic mechanisms and offers a significant theoretical foundation for developing highly selective photocatalysts. Full article

Antibiotic resistance has been recognized as a global threat to human health. Therefore, it is urgent to develop effective strategies to address the contamination of water environments caused by antibiotics. In this study, Fe/Mn bimetallic-modified biochar (FMBC) was synthesized through a one-pot oxidation/reduction-hydrothermal co-precipitation method, demonstrating an exceptional photocatalytic-Fenton degradation performance for oxytetracycline (OTC). Characterization techniques including FTIR, SEM, XRD, VSM, and N₂ adsorption–desorption analysis confirmed that the Fe/Mn bimetals were successfully loaded onto the surface of biochar in the form of Fe₃O₄ and MnFe₂O₄ mixed crystals and exhibited favorable paramagnetic properties that facilitate magnetic recovery. A key innovation is the utilization of biochar’s inherent phenol/quinone structures as reactive sites and electron transfer mediators, which synergistically interact with the loaded bimetallic oxides to significantly enhance the generation of highly reactive ·OH radicals, thereby boosting catalytic activity. Even after five recycling cycles, the material exhibited minimal changes in degradation efficiency and bimetallic crystal structure, indicating its notable stability and reusability. The photocatalytic degradation experiment conducted in a Fenton-like reaction system demonstrates that, under the conditions of pH 4.0, a H₂O₂ concentration of 5.16 mmol/L, a catalyst dosage of 0.20 g/L, and an OTC concentration of 100 mg/L, the optimal degradation efficiency of 98.3% can be achieved. Additionally, the pseudo-first-order kinetic rate constant was determined to be 4.88 min⁻¹. Furthermore, this study elucidated the detailed degradation mechanisms, pathways, and the influence of various ions, providing valuable theoretical insights and technical support for the degradation of antibiotics in real wastewater. Full article

Owing to global energy demands and climate change resulting from fossil fuel use, technologies capable of converting greenhouse gases into renewable energy resources are needed. One such technology is photocatalytic CO₂ reduction, which utilises solar energy to transform CO₂ into value-added hydrocarbons. However, the application of photocatalytic CO₂ reduction is limited by the inefficiency of existing photocatalysts. In this study, we developed a nitrogen-deficient g-C₃N₄-confined PtCu dual-atom catalyst (PtCu/V_N-C₃N₄) for photocatalytic CO₂ reduction. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy confirmed the atomic-level anchoring of PtCu pairs onto the nitrogen-vacancy-rich g-C₃N₄ nanosheets. The optimised PtCu/V_N-C₃N₄ exhibited superior photocatalytic performance, with CO and CH₄ evolution rates of 13.3 µmol/g/h and 2.5 µmol/g/h, respectively, under visible-light irradiation. Mechanistic investigations revealed that CO₂ molecules were preferentially adsorbed onto the PtCu dual sites, initiating a stepwise reduction pathway. In situ diffuse reflectance infrared Fourier-transform spectroscopy identified the formation of a key intermediate (HCOO*), whereas interfacial wettability studies demonstrated efficient H₂O adsorption on PtCu sites, providing essential proton sources for CO₂ protonation. Photoelectrochemical characterisation further confirmed the enhanced charge-transfer kinetics in PtCu/V_N-C₃N₄, which were attributed to the synergistic interplay between the nitrogen vacancies and dual-atom sites. Notably, the dual-active-site architecture minimised the competitive adsorption between CO₂ and H₂O molecules, thereby optimising the surface reaction pathways. This study establishes a rational strategy for designing atomically precise dual-atom catalysts through defect engineering, achieving concurrent improvements in activity, selectivity, and charge carrier utilisation for solar-driven CO₂ conversion. Full article

This study evaluated the relationship between the microstructure, photoluminescence, and photocatalytic properties of newly synthesized nanostructured phosphor materials. The combustion method was used to create samples of down-converting SrGd₂O₄ doped with Dy³⁺ ions (1, and 7 at%) and up-converting SrGd₂O₄ co-doped with varying quantities of Yb³⁺ ions (2, and 6 at%) and a constant quantity of Ho³⁺ ions (1 at%). Transmission electron microscopy (TEM) revealed the existence of porous agglomerated round-shaped particles, with the size around 150 nm, arranged in network-like structures. Energy dispersive X-ray spectroscopy (EDS) confirmed the presence of all structural elements and their homogeneous distribution throughout the particles. The presence of specific emission peaks associated with Dy³⁺ or Ho³⁺ dopant ions was demonstrated by luminescent measurement. The degradation processes of specific organic dyes (methylene blue for up-converters and rhodamine B for down-converters) under simulated sun irradiation were used to investigate photocatalytic activity. A reduction in dye concentration in aqueous solutions was measured using UV/Vis absorption spectroscopy. The results showed a successful dye breakdown rate after 4 h, and aliquots of the working solutions were obtained at precise intervals. Additionally, the results indicated that samples with the highest luminescence intensity exhibited superior photocatalytic activity, suggesting a significant promise for usage as multifunctional materials. Full article

To enhance the performance of photocatalytic CO₂ reduction, the development of suitable cocatalysts represents an effective strategy. Cocatalysts can interact with photocatalysts to improve light absorption capabilities and facilitate the separation and transfer of photogenerated electrons and holes. Moreover, they provide highly active surface sites that promote the adsorption and activation of CO₂, which leads to acceleration of photocatalytic reduction. Herein, WO₃ is employed as a cocatalyst to promote the CO₂ photoreduction performance of a g-C₃N₄-TiO₂ heterojunction through a facile and scalable calcination method. In pure water, optimal WO₃/g-C₃N₄-TiO₂ (WCT) delivers high selectivity CO and CH₄ formation of 48.31 µmol·g⁻¹ and 77.18 µmol·g⁻¹ in the absence of a sacrificial reagent and extra photosensitizer, roughly 13.9 and 45.7 times higher than that of g-C₃N₄-TiO₂ (CT). WO₃ can strongly interact with g-C₃N₄-TiO₂ electronically, guiding electrons across the interface to the surface. The oxygen vacancies in WO₃, as electron-enriched centers, not only enhance charge separation and form efficient charge transfer channels but also capture photogenerated electrons to suppress charge recombination. This strong interaction and oxygen vacancies in WO₃ jointly improve photocatalytic CO₂ reduction activity and selectivity, offering a feasible way to design efficient cocatalysts. Full article

Addressing the limitations of poor piezoelectric photocatalytic activity and insufficient magnetic recovery in pure BiFeO₃ nanoparticles, Gd and Zr co-doped BiFeO₃ nanoparticles were synthesized via the sol-gel method. The structural characterization revealed a rhombohedral-to-orthorhombic phase transition with reduced grain size (~35 nm) and lattice distortion due to dopant incorporation. An XPS analysis confirmed Fe³⁺ dominance and oxygen vacancy enrichment, while optimized BGFZ9 exhibited enhanced remanent magnetization (0.1753 emu/g, 14.14 increase) compared to undoped BFO. The synergistic piezo-photocatalytic system achieved 81.08% Ofloxacin degradation within 120 min (rate constant: 0.0136 min⁻¹, 1.26 higher than BFO) through stress-induced piezoelectric fields that promoted electron transfer for ·O₂⁻/·OH radical generation via O₂ reduction. The Ofloxacin degradation efficiency decreased to 24.36% after four cycles, with structural integrity confirmed by XRD phase stability. This work demonstrates a triple-optimization mechanism (crystal phase engineering, defect modulation, and magnetic enhancement) for designing magnetically recoverable multiferroic catalysts in pharmaceutical wastewater treatment. Full article

This research aimed to co-produce CQDs and hydrochar from natural sources to improve the photocatalytic properties of TiO₂. Juice extract from Citrus lemon fruits from south-eastern Spain was used as the carbon precursor. The synthesis strategy of the CQDs and hydrochar (Hc) was divided into different stages aimed at figuring out the role of the temperature (180, 220, 250 °C), the addition of TiO₂ nanoparticles, and the presence of N-/P-donor compounds (ethylenediamine and orto-phosphoric acid) in the photocatalytic properties of final composites. The results revealed that at 250 °C, using agro-carbon materials as Hc, and the addition of N-donor compounds, improved the photocatalytic activity and photodegradation rate of TiO₂ over methyl orange (MO) under blue light by 1000% and 2700%, respectively, with the parallel reduction of TiO₂ bandgap from 3.5 eV (Uv light) to 3.00 eV (visible light). These results are related to the ability of the carbon materials (electronegative) to enhance the formation of a Ti³⁺-active state. This study provides a landscape for a one-step method for the production of agro-carbon/TiO₂ photocatalysts with high activity under visible light as an efficient and sustainable strategy for applications such as energy generation and water purification under sunlight. Full article

The enduring problem of CO₂ emissions and their consequent influence on the earth’s atmosphere has captured the attention of researchers. Photocatalytic CO₂ reduction holds great significance; however, it is constrained by the effect of carrier recombination. Simultaneously, the structural modification of heterojunction catalysts has emerged as a promising approach to boost the photocatalytic performance. Herein, Zn₂GeO₄@CeO₂ core@shell nanorods were prepared by a simple self-assembly method for photocatalytic CO₂ reduction. The thickness of the CeO₂ shell can be regulated rapidly and conveniently. The photocatalytic results indicate that the structure regulation could affect the photocatalytic performance by controlling the amount of active sites and the shielding effect. X-ray photoelectron spectroscopy (XPS) and Mott–Schottky analyses reveal that Zn₂GeO₄ and CeO₂ formed Type-I heterojunctions, which prolonged the lifetime of the photogenerated carriers. The CO₂ adsorption and activation capacities of CeO₂ also exert a beneficial influence on the progress of CO₂ photoreduction, thus enabling efficient photocatalytic CO₂ reduction. Moreover, the in situ FT-IR spectra show that Zn₂GeO₄@CeO₂ suppresses the formation of byproduct intermediates and shows higher CO selectivity. The best sample of Zn₂GeO₄@0.07CeO₂ can exhibit a CO yield of as high as 1190.9 μmol g⁻¹ h⁻¹. Full article

The urgent need for sustainable CO₂ conversion technologies has driven the development of advanced photocatalysts that harness solar energy. This study employs a CTAB-assisted solvothermal method to fabricate a Z-scheme heterojunction Fe-MOFs/V_O-Bi₂WO₆ (FM/V_O-BWO) for photocatalytic CO₂ reduction. Positron annihilation lifetime spectroscopy (PALS) was employed to confirm the existence of oxygen vacancies, while spherical aberration-corrected transmission electron microscope (STEM) characterization verified the successful construction of heterointerfaces. X-ray absorption fine structure (XAFS) spectra confirmed that the defect configuration and heterostructure changed the surface chemical valence state. The optimized 1.0FM/V_O-BWO composite demonstrated exceptional photocatalytic performance, achieving CO and CH₄ yields of 60.48 and 4.3 μmol/g, respectively, under visible-light 11.8- and 1.5-fold enhancements over pristine Bi₂WO₆. The enhanced performance is attributed to oxygen vacancy-induced active sites facilitating CO₂ adsorption/activation. In situ molecular spectroscopy confirmed the formation of critical CO₂-derived intermediates (COOH* and CHO*) through surface interactions involving four-coordinated and two-coordinated hydrogen-bonded water molecules. Furthermore, the accelerated interfacial charge transfer efficiency mediated by the Z-scheme heterojunction has been conclusively demonstrated. This work establishes a paradigm for defect-mediated heterojunction design, offering a sustainable route for solar fuel production. Full article

Converting carbon dioxide (CO₂) into high-value fuels through the photothermal effect offers an effective approach to enhancing the carbon cycle and reducing the greenhouse effect. In this study, we developed Ag/C-TCN-x, a carbon nitride-based photocatalyst that integrates both photothermal and localized surface plasmon resonance (LSPR) effects. This material was synthesized through a three-step process involving hydrothermal treatment, calcination, and photo-deposition. Real-time infrared thermography monitoring revealed that Ag/C-TCN-2 reached a surface stabilization temperature of approximately 176 °C, which was 1.5 times higher than C-TCN and 2.2 times higher than g-C₃N₄. Under the same experimental conditions, Ag/C-TCN demonstrated a carbon monoxide (CO) release rate 3.3 times greater than that of pure g-C₃N₄. The composite sample Ag/C-TCN-2 maintained good photocatalytic activity in five cycling tests. The structural stability of the sample after the cycling tests was confirmed by X-ray diffraction (XRD) test. The unique tubular structure of Ag/C-TCN increased its specific surface area, facilitating enhanced CO₂ adsorption. Carbon doping not only triggered the photothermal effect but also accelerated the conversion of carriers. Additionally, the LSPR effect of Ag nanoparticles, combined with carbon doping, optimized charge carrier dynamics and promoted efficient CO₂ photoreduction. The CO₂ reduction mechanism over Ag/C-TCN was further examined using in situ Fourier Transform Infrared (FT-IR) spectroscopy. This research offers valuable insights into how photothermal and LSPR effects can be harnessed to enhance the efficiency of CO₂ photoreduction. Full article