Ternary dual S-scheme In2O3/SnIn4S8/CdS heterojunctions for boosted light-to-hydrogen conversion

Emerging Trends in CdS-Based Nanoheterostructures: From Type-II and Z-Scheme toward S-Scheme Photocatalytic H2 Production

Cadmium sulfide (CdS) based heterojunctions, including type-II, Z-scheme, and S-scheme systems emerged as promising materials for augmenting photocatalytic hydrogen (H2) generation from water splitting. This review offers an exclusive highlight of their fundamental principles, synthesis routes, charge transfer mechanisms, and performance properties in improving H2 production. We overview the crucial roles of Type-II heterojunctions in enhancing charge separation, Z-scheme heterojunctions in promoting redox potentials to reduce electron-hole (e-/h+) pairs recombination, and S-scheme heterojunctions in combining the merits of both type-II and Z-scheme frameworks to obtain highly efficient H2 production. The importance of this review is demonstrated by its thorough comparison of these three configurations, presenting valuable insights into their special contributions and capability for augmenting photocatalytic H2 activity. Additionally, key challenges and prospects in the practical applications of CdS-based heterojunctions are addressed, which provides a comprehensive route for emerging research in achieving sustainable energy goals.

Construction of a novel S-scheme AgVO3/CaIn2S4 heterostructure for efficient photodegradation of tetracycline hydrochloride

Constructing an S-scheme system with highly active catalysts is a significant approach for improving the separation of photoinduced carriers to solve the related environmental aggravation. In this study, a well-designed S-scheme AgVO3/CaIn2S4 photocatalyst was synthesized for water purification by in situ growing CaIn2S4 nanocrystals on AgVO3 nanorod surfaces. The optimized AgVO3/CaIn2S4 heterostructure demonstrates an enhanced photocatalytic efficiency (94.1%) toward tetracycline hydrochloride (TCH) degradation compared with bare AgVO3 (42.6%) and CaIn2S4 (81.6%). The significant enhancement of photocatalytic activity is attributed to the S-scheme charge transfer mechanism in the AgVO3/CaIn2S4 heterostructure, which effectively directs photogenerated charge migration, boosts charge transfer, and preserves the high redox capacity of photoexcited electrons and holes on different active sites. This study is expected to offer insights into strategically designing and preparing S-scheme heterojunction photocatalysts to improve water purification.

Semimetal 1T' phase molybdenum sulfide decorated on zinc indium sulfide with S-scheme heterojunction for enhanced photocatalytic hydrogen evolution

Heterojunction engineering is an effective strategy to improve photocatalytic performance. Two-dimensional (2D)/2D semimetal 1T' phase molybdenum sulfide/zinc indium sulfide (1T'-MoS2/ZnIn2S4) S-scheme heterojunctions with tight and stable interfaces were synthesized by a simple hydrothermal synthesis method. Under the optimal 1T'-MoS2 loading ratio (5 wt%), the hydrogen production rate of 1T'-MoS2/ZnIn2S4 composites reaches 11.42 mmol h-1 g-1, which is 3.1 and 1.4 times higher than that of pure ZnIn2S4 (2.9 mmol h-1 g-1) and ZnIn2S4/Pt (8.01 mmol h-1 g-1), and the apparent quantum efficiency (AQE) reaches 53.17 % (λ = 370 nm). Semimetal 1T' phase MoS2 on ZnIn2S4 broadens the light absorption range, enhances the light absorption ability, promotes electron transfer, and offers abundant active sites. The establishment of S-scheme heterojunctions achieves the spatial separation of photogenerated charges and increases the reduction potential. This work provides insights for the design of novel photocatalysts.

Chitosan synergizes with bismuth-based metal-organic frameworks to construct double S-type heterojunctions for enhancing photocatalytic antimicrobial activity

In recent years, photocatalytic technology has been introduced to develop a new kind antimicrobial agents fighting antibiotic abusing and related drug resistance. The efforts have focused on non-precious metal photocatalysts along with green additives. In the present work, a novel bis-S heterojunctions based on the coupling of polysaccharide (CS) and bismuth-based MOF (CAU-17) s synthesized through a two-step method involving amidation reaction under mild conditions. The as prepared photocatalyst literally extended the light response to the near-infrared region. Owing to its double S-type heterostructure, the lifetime of the photocarriers is significantly prolonged and the redox capacity are enhanced. As a result, the as prepared photocatalyst indicated inhibition up to 99.9 % under 20 min of light exposure against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria as well as drug-resistant bacteria (MRSA). The outstanding photocatalytic performance is attributed to the effective charge separation and migration due to the unique double S heterostructure. Such a double S heterostructure was confirmed through transient photocurrent response, electrochemical impedance spectroscopy tests and electron spin resonance measurements. The present work provides a basis for the simple synthesis of high-performance heterojunction photocatalytic inhibitors, which extends the application of CAU-17 in environmental disinfection and wastewater purification.

Sulfur vacancy-rich (α/β-CdS)/SiO2 photocatalysts for enhanced visible-light-driven photocatalytic degradation of rhodamine B

The development of highly efficient photocatalysts for visible-light-driven degradation of organic pollution is of great interest for wastewater purification. In this work, a sulfur vacancy-rich (α/β-CdS)/SiO2 (α: hexagonal & β: cubic) photocatalyst with a high catalytic activity was novelly synthesized on a nano-SiO2 carrier by the reaction of Cd2+ with a CS2 storage material (CS2SM) as sulfur source and crystalline modifiers. The dispersion of α/β-CdS on the nano-SiO2 carrier significantly enhanced the visible-light-driven catalytic activity of (α/β-CdS)/SiO2 photocatalyst, and 93.37 % rhodamine B (RhB) conversion was determined over 50 mg (α/β-CdS)/SiO2 photocatalyst for 30 mL 400 mg/L RhB solution at light intensity of 150 mW/cm2 and 298.15 K. After five cycle tests, the (α/β-CdS)/SiO2 photocatalyst still owned excellent visible-light-driven catalytic degradation stability (>90 %). The characterizations of morphology, functional groups, and photo-electrochemistry of (α/β-CdS)/SiO2 photocatalyst demonstrated that nano-SiO2 as a carrier played meaningful role in dispersing α/β-CdS and reducing agglomeration, thus increasing the active site of photocatalytic degradation reaction, and the presence of α/β hetero-phase junctions and sulfur vacancies allows the rapid separation of photo-generated carriers and inhibits photo-generated electron-holes recombination. Meanwhile, the electron paramagnetic resonance (EPR) and free radical masking test have also proved that the main active species is ·O2- for the oxidation of RhB. Therefore, the work is providing a new reference to the visible-light-driven degradation of wastewater with high RhB concentration at room temperature.