p_Aminophenol, namely 4-aminophenol (4-AP), is an aromatic compound including hydroxyl and amino groups contiguous together on the benzene ring, which are suitable chemically reactive, amphoteric, and alleviating agents in nature. Amino phenols are appropriate precursors for synthesizing oxazoles and oxazines. However, since the toxicity of aniline and phenol can harm human and herbal organs, it is essential to improve a reliable technique for the determination of even a trace amount of amino phenols, as well as elimination or (bio)degradation/photodegradation of it to protect both the environment and people's health. For this purpose, various analytical methods have been suggested up till now, including spectrophotometry, liquid chromatography, spectrofluorometric and capillary electrophoresis, etc. However, some drawbacks such as the requirement of complex instruments, high costs, not being portable, slow response time, low sensitivity, etc. prevent them to be employed in a wide range and swift in-situ applications. In this regard, besides the efforts such as (bio)degradation/photodegradation or removal of 4-AP pollutants from real samples, electroanalytical techniques have become a promising alternative for monitoring them with high sensitivity. In this review, it was aimed to emphasize and summarize the recent advances, challenges, and opportunities for removal, degradation, and electrochemical sensing 4-AP in real samples. Electroanalytical monitoring of amino phenols was reviewed in detail and explored the various types of electrochemical sensors applied for detecting and monitoring in real samples. Furthermore, the various technique of removal and degradation of 4-AP in industrial and urban wastes were also deliberated. Moreover, deep criticism of multifunctional nanomaterials to be utilized as a catalyst, adsorbent/biosorbent, and electroactive material for the fabrication of electrochemical sensors was covered along with their unique properties. Future perspectives and conclusions were also criticized to pave the way for further studies in the field of application of up-and-coming nanostructures in environmental applications. 

State-of-art advances on removal, degradation and electrochemical monitoring of 4-aminophenol pollutants in real samples: A review.

Here, an S-scheme heterojunction was constructed on the basis of the modification of a Ni-based metal-organic framework (Ni-MOF) by different in situ treatment strategies. First, NiS2, NiO, and Ni2P were derived in situ on the surface of Ni-MOF through surface sulfonation, oxidation, and phosphatizing treatments. They can efficiently accept the electrons from the conduction band of Ni-MOF as the trap centers, thus improving the hydrogen production activity. Additionally, phosphatizing makes the electronegativity of Ni-MOF/P stronger than that of the original Ni-MOF, which can enhance the absorption of protons, thus promoting the hydrogen evolution reaction. Next, the S-scheme heterojunction was successfully built by the coupling of 2D CeO2 with Ni-MOF/P. The maximum hydrogen production rate of the hybrid catalyst (6.337 mmol g-1 h-1) is 14.18 times that of the untreated Ni-MOF due to the full utilization of photo-induced electrons. Finally, the probable hydrogen evolution mechanism was proposed by analyzing a series of characterization results and by the density functional theory (DFT) calculation.

2D CeO2 and a Partially Phosphated 2D Ni-Based Metal-Organic Framework Formed an S-Scheme Heterojunction for Efficient Photocatalytic Hydrogen Evolution.

Sparked by natural photosynthesis, solar photocatalysis using metal‐free graphitic carbon nitride (g‐C3N4) with appealing electronic structure has turned up as the most captivating technique to the quest for sustainable energy generation and pollution‐free environment. Nonetheless, low‐dimensional g‐C3N4 is thwarted from sluggish kinetics and rapid recombination of photogenerated carriers upon light irradiation. Among multifarious modification strategies, engineering 2D cocatalysts is anticipated to accelerate redox kinetics, augment active sites and ameliorate electron–hole separation of 2D g‐C3N4 for boosted activity thanks to its face‐to‐face contact surface. It is of timely and technological significance to review the 2D/2D interfaces with state‐of‐the‐art 2D cocatalysts, spanning from carbon‐containing to phosphorus‐containing, metal dichalcogenide, and other cocatalysts. Fundamental principles for each photocatalytic application will be introduced. Thereafter, the recent advances of 2D/2D cocatalyst‐mediated g‐C3N4 systems will be critically evaluated based on their interfacial engineering, emerging roles, and impacts toward stability and catalytic efficiency. Importantly, mechanistic insights into the charge dynamics and structure–performance relationship will be deciphered. Last, noteworthy research directions are prospected to deliver insightful ideas for future development of g‐C3N4. Overall, this review is anticipated to serve as a scaffold and cornerstone in designing dimensionality‐dependent 2D cocatalyst‐assisted g‐C3N4 toward renewable energy and ecologically green environment.

Tailor‐Engineered 2D Cocatalysts: Harnessing Electron–Hole Redox Center of 2D g‐C3N4 Photocatalysts toward Solar‐to‐Chemical Conversion and Environmental Purification

Two-dimensional (2D) molybdenum disulfide (MoS2)–based materials are of great interest because of their capacity to efficiently absorb electromagnetic spectrum in the visible region. Starting from the structural and electronic properties, this review discusses the synthesis strategies of 2D MoS2. The major photocatalytic applications of 2D MoS2 such as hydrogen evolution, pollutant degradation, self-cleaning, photoelectrochemical water splitting, and microbial disinfection are summarized. The mechanistic understanding of various photocatalytic applications of 2D MoS2 is summarized through schematic diagrams. In addition, this review outlines the methodologies for improving the 2D MoS2 photocatalysts and recapitulates the research directions in this area of semiconductor photocatalysis.

2D MoS2: structure, mechanisms, and photocatalytic applications

A visible-light sensitive MoSSe nanohybrid for the photocatalyticdegradationof tetracycline, oxytetracycline, and chlortetracycline.

Lamellar flower-like porous MoS2 as an efficient cocatalyst to boost photocatalytic hydrogen evolution of CdS

Promotion effect of rhenium on MoS2/ReS2@CdS nanostructures for photocatalytic hydrogen production

Cu2O-based materials are potential adsorbents for the removal of anionic dyes pollutions. Herein, sulfur incorporation is designed to promote adsorption capacity of Cu2O. A series of sulfur-incorporated Cu2O nanomaterials are synthesized by a facile chemical reduction method. Sulfur incorporation favors the formation of small sized S-Cu2O particles in the range of 50–100 nm and their enhanced adsorption performances. The S-Cu2O particles show good adsorption activities for methyl orange solution (75–500 mg L−1) under pH 6–10 at room temperature. A superior adsorption capacity of 1485.24 mg g−1 for the removal of methyl orange is achieved on the S-Cu2O adsorbent. Adsorption behaviors of the S-Cu2O adsorbent fit well with Langmuir isotherm and pseudo-second-order kinetic model. Adsorption thermodynamic results indicate the exothermic and spontaneous adsorption process. Anionic dye can be adsorbed selectively on the S-Cu2O adsorbent and separated from cationic dyes. Density functional theory calculations prove a pronounced electron accumulation on sulfur sites, benefiting to the adsorption on S-Cu2O. A nonmetallic element incorporation for improving adsorption capacity of metal oxide adsorbents is provided as a promising strategy for other adsorbents.

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Enhanced selective adsorption ability of Cu 2 O nanoparticles for anionic dye by sulfur incorporation

Photocatalytic reactions over effective photocatalysts are attractive to explore clean hydrogen energy from water with the utilization of solar energy. Ternary Co1-xS@ZnCoS/CdS (ZCS/CdS) composites are constructed as photocatalysts through the hydrothermal formation of Co1-xS and ZnCoS nanoparticles on CdS nanorods. Superior to the binary Co1-xS/CdS composite, ZCS/CdS shows the improved photocatalytic activity with a hydrogen production rate of 58.4 mmol·g-1·h-1, which is 31.4 and 2.1 times higher than those of CdS and Co1-xS/CdS, respectively. Different from binary Co1-xS/CdS, the participation of a small amount of zinc favors the formation of ZnCoS solid solution in ZCS/CdS. A synergistic promotion effect of ZnCoS and Co1-xS is confirmed due to tight heterojunctions among Co1-xS, ZnCoS, and CdS in ZCS/CdS. The unique heterostructure of ZCS/CdS benefits its enhanced absorption ability of visible light, accelerating the separation of photoinduced electron-hole pairs and the electron transfer. ZCS/CdS exhibits the strong reduction ability and superior photocatalytic stability due to the role of double Z-scheme electron transfer pathways in the ternary composite. This work provides a suitable way to tune noble metal-free composite photocatalysts for efficient H2 production.

Junwen Wang

Papers

Lamellar flower-like porous MoS2 as an efficient cocatalyst to boost photocatalytic hydrogen evolution of CdS

Promotion effect of rhenium on MoS2/ReS2@CdS nanostructures for photocatalytic hydrogen production

Enhanced selective adsorption ability of Cu 2 O nanoparticles for anionic dye by sulfur incorporation

Synergistic Promotion Effect of ZnCoS Solid Solution and Co1-xS on Photocatalytic Hydrogen Production of the CdS Composite.