Dual modification of BiVO4 photoanode for synergistically boosting photoelectrochemical water splitting

BiVO4/Bi4V2O10 isometallic heterojunction coupled with FeOOH/NiOOH cocatalysts for efficient photoelectrochemical water oxidation

The four-electron water oxidation reaction in photoelectrochemical systems poses a major challenge to efficiently converting solar energy into chemical energy amid the global energy crisis. Herein, we report a strategy to develop a photoelectrochemical system using BiVO4/Bi4V2O10 isometallic heterojunction photoanodes paired with FeOOH/NiOOH cocatalysts to enhance water oxidation in neutral electrolytes. The results demonstrate that the BiVO4/Bi4V2O10/FeOOH/NiOOH photoanode achieves a photocurrent density of 4.48 mA/cm2 at 1.23 V versus the reversible hydrogen electrode and an applied bias photon-to-current efficiency of 1.69 % at 0.63 V versus the reversible hydrogen electrode-significantly outperforming bare BiVO4. This enhanced photoelectrochemical performance is attributed to the identical elemental composition and well-aligned energy band positions of Bi4V2O10 and BiVO4, which minimize charge recombination at the interface. Additionally, the FeOOH/NiOOH double-layer cocatalyst facilitates rapid transfer of photogenerated carriers, as confirmed by femtosecond transient absorption spectroscopy and transient photovoltage measurements. This approach provides a novel and effective pathway for advancing high-efficiency photoelectrochemical cells.

Recent advances in BiVO4-based heterojunction photocatalysts for energy and environmental applications

Photocatalytic technology offers a promising solution by efficiently converting solar energy into chemical energy and addressing environmental pollution. BiVO4 is a promising semiconductor photocatalytic material due to its narrow band gap, good visible light response, and non-toxicity. Recently, there has been significant interest in developing BiVO4-based heterojunction photocatalysts to overcome the challenges of rapid recombination rate of photogenerated charge carriers and insufficient electron transport capacity in pure BiVO4. However, a comprehensive and systematic summary of the role of BiVO4-based heterojunction catalysts in improving photocatalytic performance is lacking. This review covers the mechanisms, challenges, and classification of BiVO4-based heterojunction photocatalysis. It also summarizes recent advancements in using these photocatalysts for energy and environmental applications, such as water splitting, nitrogen fixation, carbon dioxide reduction, pollutant degradation, etc. Perspectives on the existing challenges, potential solutions, and prospects of BiVO4-based heterojunction photocatalysts are outlined, aiming to offer valuable insights to accelerate their commercialization as high-performance photocatalysts.

Surfactants Modulating of BiVO4 on Photocatalytic Property as a Regulation of Surface Free Energy

BiVO4 is a stable photocatalytic material but has poor photocatalytic activity in visible light. Herein, the surfactants were investigated to enhance the photocatalytic degradation of tetracycline (TC) of BiVO4 through a hydrothermal method. The different molecular structures and properties of surfactant-modified BiVO4 show clustered small spheres and stacked plate-like microcrystals. The N-hexadecyltrimethylammonium chloride (CTAC)-modified BiVO4 (BiVO4-CTAC) with stacked plate-like morphology increases the light absorption range and decreases the energy band gap. Surfactants with different hydrophilic groups and molecular structures affect the formation process of BiVO4, regulating the morphology, crystal structure, and crystalline surface exposure of BiVO4. BiVO4-CTAC has demonstrated superior TC degradation efficiency compared with the original BiVO4 (BiVO4-Blank). This enhancement is attributed to the observation in the Nyquist plot, where BiVO4-CTAC exhibits the smallest arc radius, indicative of reduced charge transfer resistance and improved charge separation. Furthermore, holes (h+) and superoxide radicals (•O2-) reactive species are the main active radicals for TC photocatalytic degradation. This study develops a novel method to synthesize monoclinic phase lamellar BiVO4 materials by simply changing the surfactant type. This study holds potential implications for advancing surfactant-assisted synthesis of high-efficiency photocatalysts.

Effective Improvement of Thermodynamics and Kinetics of BiVO4 Photoanode via CuI for Photoelectrochemical Water Oxidation

The preparation of durable and efficient photoanodes for photoelectrochemical water oxidation is of great importance in promoting the development of green hydrogen production and artificial photosynthesis. Here, n-type BiVO4 was combined with p-type CuI to construct a CuI/BiVO4 (CIB-1) p-n heterojunction photoanode. The composite photoanode effectively overcame the drawbacks of BiVO4, such as low separation and injection efficiency of photogenerated electron-hole pairs. As a result, the CIB-1 had the highest photocurrent density of 1.98 mA cm-2, which was 2.5 times higher than pure BiVO4 with 0.79 mA cm-2 at 1.23 V (vs RHE) under AM 1.5G light irradiation. The CIB-1 had a lower Tafel slope of 23.2 mV decade-1 compared to 47.9 mV decade-1 for BiVO4, so the water oxidation kinetics was remarkably advanced over CuI/BiVO4. Based on DFT calculations, the OER overpotential of 0.480 V for CuI/BiVO4 was significantly lower than that of 1.546 V for BiVO4 due to the lower free energy from OH- to oxygen over CuI/BiVO4 compared to BiVO4.

Photocatalytic degradation of perfluorooctanoic acid (PFOA) from water: A mini review

Perfluorooctanoic acid (PFOA) has drawn increasing attention as a highly persistent organic pollutant. The inherent stability, rigidity and potential toxicities characteristics make it a challenge to develop efficient technologies to eliminate it from water. Photocatalytic technology, as one advanced method, has been widely used in the degradation of PFOA in water. In this review, recent progress in the design of photocatalysts including doping, defects engineering, heterojunction and surface modification to boost the photocatalytic performance toward PFOA is summarized. The relevant degradation mechanisms were also discussed in detail. Finally, future prospect and challenges are proposed. This review may provide new guidelines for researchers to design much more efficient photocatalysts applied in the elimination of PFOA.