Co2+ substituted for Bi3+ in BiVO4 and its enhanced photocatalytic activity under visible LED light irradiation

Advanced photocatalytic materials based degradation of micropollutants and their use in hydrogen production - a review

The use of pharmaceuticals, dyes, and pesticides in modern healthcare and agriculture, along with expanding industrialization, heavily contaminates aquatic environments. This leads to severe carcinogenic implications and critical health issues in living organisms. The photocatalytic methods provide an eco-friendly solution to mitigate the energy crisis and environmental pollution. Sunlight-driven photocatalytic wastewater treatment contributes to hydrogen production and valuable product generation. The removal of contaminants from wastewater through photocatalysis is a highly efficient method for enhancing the ecosystem and plays a crucial role in the dual-functional photocatalysis process. In this review, a wide range of catalysts are discussed, including heterojunction photocatalysts and various hybrid semiconductor photocatalysts like metal oxides, semiconductor adsorbents, and dual semiconductor photocatalysts, which are crucial in this dual function of degradation and green fuel production. The effects of micropollutants in the ecosystem, degradation efficacy of multi-component photocatalysts such as single-component, two-component, three-component, and four-component photocatalysts were discussed. Dual-functional photocatalysis stands out as an energy-efficient and cost-effective method. We have explored the challenges and difficulties associated with dual-functional photocatalysts. Multicomponent photocatalysts demonstrate superior efficiency in degrading pollutants and producing hydrogen compared to their single-component counterparts. Dual-functional photocatalysts, incorporating TiO2, g-C3N4, CeO2, metal organic frameworks (MOFs), layered double hydroxides (LDHs), and carbon quantum dots (CQDs)-based composites, exhibit remarkable performance. The future of synergistic photocatalysis envisions large-scale production facilitate integrating advanced 2D and 3D semiconductor photocatalysts, presenting a promising avenue for sustainable and efficient pollutant degradation and hydrogen production from environmental remediation technologies.

Photocatalytic Degradation of Crystal Violet on Cu, Zn Doped BiVO4 Particles

Fabrication of codoped photocatalysts is a developing area of research. Herein, we explore the visible light photocatalytic properties of Cu, Zn codoped BiVO4 particles. Doping lower valent cations (Cu and Zn) makes the BiVO4 surface more acidic and enables us to target the basic crystal violet (CV) dye. The adopted hydrothermal protocol of synthesis results in the formation of Cu-Zn codoped monoclinic BiVO4 particles. Undoped monoclinic BiVO4, prepared by the same protocol, showed significant formation of oxygen vacancies. XPS analyses confirm the coexistence of Cu2+/Cu+ and Zn2+ dopants. Increased dopant percentage reduced oxygen vacancies. XRD indicates that Cu2+/Cu+ or Zn2+ dopants generally substitute Bi3+ in BiVO4. All photocatalysis activities for CV degradation are reported under near-neutral pH conditions. A typical codoped BiVO4 photocatalyst with 1% Zn and 2% Cu demonstrated the best CV degradation photocatalytic activity. The activity of this Zn, Cu codoped photocatalyst is better than that of pure, Zn-doped, and Cu-doped BiVO4 samples. Active species trapping experiments indicated the possible photocatalysis mechanism. The photocatalysts exhibited appropriate recyclability and photostability.

Investigations of microwave absorption performance of bi-layer absorber composed of FeWO4 & BiVO4 nanocomposite powder in 2-18 GHz

Optimization necessitates every feature to be scrutinized associated with enhancement for microwave absorption. So, interplay between simulation and experiment is a significant aspect to find optimal findings in this regard. Herein, microwave absorption characteristics of as-prepared FeWO₄ and BiVO₄ nanomaterials were investigated by preparing mono layer and bilayer samples. For the bilayer samples, simulation technique was used to regulate microwave absorption efficiency. Using simulation technique, bilayer sample has achieved a minimum reflection loss (RL_min) of -42 dB with BiVO₄ as a top layer (0.6 mm thickness) and FeWO₄ as a bottom layer (0.8 mm thickness) with effective absorption Bandwidth (EAB) of 13 GHz (15-2 GHz) at 8.2 GHz frequency. The results show that the layered architecture of the absorbent is substantially responsible for its remarkable microwave absorption efficiency. Simulated results of the bilayer sample were also verified with experimental findings. This work provides a facile synthesis route, novel insights into the design of bilayer absorbent as well as simulation and experimental support for high-performance microwave bilayer absorber.

Nanostructured Co-doped BiVO4 for efficient and sustainable photoelectrochemical chlorine evolution from simulated sea-water

The co-production of hydrogen and chlorine from sea-water splitting could be a potential, sustainable and attractive route by any method. However, challenges to overcome are many, and critically, the sustainability and operating potential of the electrocatalyst are important. In this work, we report on Co-doping in the BiVO₄ (Co-BV) crystal lattice and employed the same as the photoanode; Co-BV exhibits a photocurrent of 190 μA cm^-2 at 1.1 V vs. RHE (the reversible hydrogen electrode) in the acidic sodium chloride solution (pH 2.3) under one sun illumination. The best-performing photoanode, with 0.05 mol% of Co doping (0.05 Co-BV), selectively produced active chlorine with 92% faradaic efficiency at 1.1 V vs. RHE by successfully suppressing the kinetically sluggish oxygen evolution reaction (OER) and the stability of the catalyst was demonstrated for up to 20 h. This is the lowest operating potential reported for the chlorine evolution reaction (CER), thus far. The overpotential required for CER with 0.05 Co-BV is lower than that of OER, which leads to selective CER at 1.1 V (vs. RHE). Co-doping into the BiVO₄ lattice decreases the charge transfer resistance and enhances the CER kinetics due to its structural and electronic integration with the BV lattice. We demonstrate that Co-doping also improves the lifetime of the charge carrier and enhances the current density of CER and sustainability of the catalyst.

Amorphous NiSn and FeOOH as bifunctional co-catalysts for oxygen reduction and phenol (water) oxidation over BiVO4 under visible light

Monoclinic BiVO₄ (BiV) has been widely used as a photoanode for water oxidation, but rarely as a photocatalyst for organic oxidation due to slow reaction of O₂. In this work, BiV has been modified with poorly crystallized sFe and sNi, where sFe is FeOOH, and sNi is a mixture of Ni(OH)₂ and polysulfide. Under light, sFe/BiV and sNi/BiV in aqueous solution were more active than BiV, respectively, not only for phenol oxidation but also for O₂ reduction. Importantly, the rate of phenol oxidation obtained for sFe/sNi/BiV was larger than the sum of the rates measured for sFe/BiV and sNi/BiV, by a factor of approximately 1.5. Moreover, on a film electrode, O₂ reduction had a current of sFe/sNi/BiV > sNi/BiV > sFe/BiV > BiV, while water (photo)oxidation had a current of sFe/sNi/BiV > sNi/BiV > sFe/BiV > BiV. A possible mechanism is proposed, involving formation of a reduced sulfur species for O₂ reduction and an oxidized iron species for phenol oxidation. In sFe/sNi/BiV, there is a mutual promotion between the sNi-mediated electron transfer and the sFe-mediated hole transfer. This results in a further improved efficiency of charge separation for O₂ reduction and phenol oxidation.

Structure, morphology and photocatalytic performance of europium doped bismuth vanadate

Europium-doped bismuth vanadate EBVO-x (0≦x≦7) with different crystalline phases have been successfully synthesized via a simple one-pot hydrothermal method. X-ray diffractometer, Raman scattering and Scanning electron microscope revealed that the...

TiO2-Based photocatalyst modified with a covalent triazine-based framework organocatalyst for carbamazepine photodegradation

A novel fluorine-doped TiO2 (TiO2-X F X ) heterojunction semiconductor photocatalyst was synthesised using covalent triazine-based frameworks (CTFs) at different weight ratios. X-ray photoelectron spectroscopy revealed that doping with CTFs shifts the value of the TiO2-X F X catalyst to a lower binding energy, which led to the bandgap narrowing. From the results of the photocatalytic activity and Fourier-transform infrared spectroscopy, a rise in carbamazepine (CBZ) adsorption under dark conditions and an increased intensity of characteristic triazine units after exfoliation were observed, which indicated that the addition of nanosheet CTFs would increase the number of active sites. Furthermore, the results showed that the TiO2-X F X /CTFs photocatalyst was almost 5.5 times better than pure TiO2-X F X in the removal of CBZ under visible light owing to the narrowed bandgap, the increased active sites, the quick separation of photo-generated carriers, and improved light absorption. A mechanism for photodegradation of CBZ with the TiO2-X F X /CTFs photocatalyst was proposed.

Synergetic effect of dual co-catalysts on the activity of BiVO4 for photocatalytic carbamazepine degradation

An efficient visible-light driven three components photocatalyst for carbamazepine (CBZ) degradation has been assembled by co-loading reduction cocatalyst Pt and oxidation cocatalyst Co₃O₄ (MnO_x) on BiVO₄. The apparent rate constant of the three components photocatalyst Pt/BiVO₄/Co₃O₄ for degradation of CBZ is 54 times that of Co₃O₄/BiVO₄ and 2.5 times that of Pt/BiVO₄, which shows a synergetic effect in the photocatalytic activity. The same synergetic effect is also observed for Pt/BiVO₄/MnO_x. The spatial separation of the reduction and oxidation cocatalysts could reduce the recombination of the photogenerated charges, which mainly accounts for the high photocatalytic activity of the three components photocatalyst. The photocatalytic intermediates of CBZ were detected by HPLC-ESI-MS, and a deductive degradation pathway of CBZ was proposed.

An efficient visible-light driven three components photocatalyst for carbamazepine (CBZ) degradation has been assembled by co-loading reduction cocatalyst Pt and oxidation cocatalyst Co₃O₄ (MnO_x) on BiVO₄. An obvious synergetic effect is observed.