Search

[Display omitted] • A flower-like CdS/K 2 Ta 2 O 6 S-scheme heterojunction was prepared. • The S-scheme charge transfer mechanism between CdS and K 2 Ta 2 O 6 was revealed. • Excellent ability for photocatalytic H 2 O 2 production from water and air. • The route and mechanism of the photocatalytic H 2 O 2 production were proposed. The hydrogen peroxide (H 2 O 2) production using solar energy is of great significance in chemical industry and environmental remediation. However, this technique requires that photocatalysts have efficient charge separation and migration efficiency. Herein, we designed a flower-like CdS/K 2 Ta 2 O 6 (CdS/KTO) S-scheme heterojunction with promoted charge separation and migration by a facile two-step hydrothermal strategy. The CdS/KTO photocatalyst exhibited an outstanding performance with a H 2 O 2 production rate of 160.89 μmol g−1 h−1 without using any sacrificial agents and adding additional O 2. The combination of the in situ irradiated X-ray photoemission spectroscopy (XPS), electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations revealed that the formation of an S-scheme heterojunction between CdS and KTO could greatly promote the separation of photogenerated electron-hole pairs toward efficient H 2 O 2 production. This work provides insights for the charge transfer mechanism of S-scheme heterojunction and an innovative stratagem for green, energy-saving and sustainable H 2 O 2 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal-organic frameworks derived low-cost Cu-doped Cu-Co 3 O 4 /NF is simply prepared. • High ammonia yield rate and FE are obtained under ultra-low nitrate concentrations. • The introduction of Cu promotes the surface-to-interior charge transfer and intrinsic activity. • The results of In-situ FTIR and DFT reveal atomic hydrogen reduction pathway. • The synergistic effect of Cu and Co suppresses the HER and drops the free energy barriers of rate determining step. The electrochemical reduction of nitrate to ammonia represents a potential approach for the valorization of waste, offering the dual benefit of mitigating various environmental concerns and concurrently yielding the valuable product of ammonia. However, on the way to its further application, the lacking of low-cost and efficient electrocatalysts under low nitrate concentrations is still one pressing issue because of the intense hydrogen evolution reaction (HER) competition and many by-products. Herein, metal–organic frameworks (MOF) derived low-cost Cu-Co 3 O 4 /NF exhibits excellent electrocatalytic activity in the low nitrate concentrations (2 mmol/L), attaining the ammonia yield rate of 0.076 mmol h−1 cm−2 and 92.4 % Faradic efficiency at −0.53 V vs. RHE. The combined results of In-situ FTIR and theoretical calculation reveal the atomic hydrogen reduction pathway, decrease in free energy of intermediate reactions and inhibition of HER of Cu-Co 3 O 4 /NF. This work introduces one economical, efficient and simple strategy and further demonstrates the superior effect of MOF derivatives in fascinating low nitrate concentration reduction to ammonia. [ABSTRACT FROM AUTHOR]

[Display omitted] • UiO-66-SO 3 H/Fe(1:1)-800 exhibited high tetracycline degradation efficiency. • The influence of operating parameters on tetracycline degradation was analyzed. • It exhibited good stability and potential for wastewater treatment applications. • Mechanism of TC degradation by heterogeneous electro-Fenton process was proposed. Designing efficient heterogeneous electro-Fenton (HEF) catalysts for in-situ H 2 O 2 generation and organic pollutant degradation in water has become a hot research topic. In this study, a series of novel UiO-66-SO 3 H/Fe(x)-800 materials were successfully prepared by carbonizing sulfonic acid metal-organic frameworks (UiO-66-SO 3 H) doped with iron for tetracycline (TC) HEF degradation. The catalytic performance of UiO-66-SO 3 H/Fe(x)-800 was evaluated by comparing different HEF systems, and the effects of different operating parameters and co-existing substances were investigated. The results indicated that UiO-66-SO 3 H/Fe(1:1)-800 displayed excellent performance for TC degradation over a broad pH range, with an optimal TC degradation efficiency of 90.10% in 90 min and a low energy consumption of 4.39 kWh/kg/TOC. Furthermore, the superior stability and reusability of this catalyst were proved in continuous cycling experiments with low iron leaching (<1.000 ug/L). The mechanism exploration demonstrated that TC was mainly oxidized by ‧OH and 1O 2. In addition, iron-doped porous carbon carrier improved the utilization rate of H 2 O 2 and accelerated the regeneration of Fe2+, which played an important role in the HEF process. The HEF system based on UiO-66-SO 3 H/Fe(1:1)-800 also exhibited satisfactory performance when treating actual water samples, presenting broad application prospects. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high catalytic activity catalyst was prepared by a one-step calcination method. • Ni 4.60 CN/PMS system performed well over a wide pH and common interferences. • The Ni-N 4 -C active site of Ni 4.60 CN mediated electron transfer pathway. • Pollutants could be selectively degraded in the Ni 4.60 CN/PMS system. Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) is a hopeful method for organic pollutants degradation. However, conventional AOPs often suffer from various disturbances in applications, such as organic matter, inorganic ions, pH, etc. Herein, a novel Ni(Ⅱ)-doped g-C 3 N 4 (Ni 4.60 CN) catalyst with Ni-N 4 -C structure was prepared, which exhibited outstanding PMS activation ability. The Ni-N 4 -C active sites facilitated the electron transfer from pollutants to PMS and achieving high selectivity toward pollutant degradation. Then, integrating experimental and theoretical results, the origin of this selectivity was revealed, indicating that organic pollutants with low vertical ionization potential (VIP), high the highest occupied molecular orbital energy (E HOMO), and low potential differences between organics and Ni 4.60 CN (marked as E PD) are more beneficial to be degraded. This study unravels the electron transfer mechanism induced by Ni-N 4 -C sites in Ni 4.60 CN /PMS activation system and provides a comprehensive insight into the selective oxidation behavior of various pollutants. [ABSTRACT FROM AUTHOR]

• Hemin derived iron and nitrogen-doped carbon catalyst exhibited high ciprofloxacin degradation and mineralization efficiency. • KHCO 3 -MgO dual-porogen improved the porous characteristics and exposed the iron sites. • Based on degradation intermediates analysis, a possible degradation pathway of CIP was proposed. • It exhibited good stability and potential for treatment of organic pollutants in wastewater. Heterogeneous electro-Fenton (HEF) technology has become a hot topic for degradation of organic pollutants in water. However, it remains a challenge to design effective catalysts for high H 2 O 2 utilization and pollutant degradation. In this work, we explored a novel iron and nitrogen-doped carbon catalyst derived from hemin (Fe-N-C) using KHCO 3 -MgO as dual-porogen. The results suggested that the KHCO 3 -MgO dual-porogen could not only improve the porous characteristics of catalyst, but also expose iron sites and change the proportion of nitrogen species. The pollutant degradation results demonstrated that the Fe-N-C-700/HEF system exhibited high ciprofloxacin degradation efficiency of 93.82% within 50 min and mineralization efficiency of 87.87% within 90 min by low energy consumption. Moreover, cycle experiments and metal ions leaching experiments revealed that the catalyst had good stability and recyclability. Electron spin resonance (ESR) test and radical capturing experiment showed that •OH was the dominant active species in this HEF system. In addition, the Fe-N-C-700/HEF system achieved satisfactory performance in the treatment of real water matrix, indicating the possibility for practical application in wastewater purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Co LDH/C, O co-doped g-C 3 N 4 2D/2D heterojunction has been first fabricated. • The modification of 2-methylimidazole enhanced photoconversion efficiency. • 2D/2D heterojunction exhibits excellent molecular oxygen activation. • The formed charge carrier transfer pathway promotes photoelectron transfer. • 2D/2D heterojunction possesses weakened surface charge carrier recombination. Molecular oxygen is a green and low-cost oxidant, which can be activated to produce reactive oxygen species by solar-light-driven photocatalysis. Here, Ni-Co LDH infused C, O co-doped g-C 3 N 4 two-dimensional (2D) ultrathin nanosheet was prepared by a simple thermal polymerization coupling hydrothermal method. The molecular oxygen activation was estimated by the quantitative determination of •O 2 − and 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation. 2D/2D heterojunction exhibits impressive photocatalytic performance. The arrestive activation efficiency is derived from the regulated energy band position, the broadened solar light absorption range, and the enhanced photoexcited electron transfer. Benefitting from these merits, the surface charge transfer efficiency of 2D/2D heterojunction is promoted to 51.3% from 14.3% (g-C 3 N 4). The surface recombination rate constant is reduced to 0.0011 s−1 from 0.0042 s−1 (g-C 3 N 4). The feasible photocatalytic mechanism for molecular oxygen activation is expounded based on experimental analysis. [ABSTRACT FROM AUTHOR]

• The characteristics of BP, h-BN, g-C 3 N 4 , graphene, and COFs are introduced. • The recent advances in element doping and heterojunction constructing are reviewed. • Organic amendment, hydroxyl modification, and dye sensitization are introduced. • The applications in HER, CO 2 RR, NRR, OER, and ORR are concluded. Semiconductor photocatalysis has been recognized as a feasible strategy for effective utilization of solar power to alleviate the energy shortage and environmental crisis. Efficient photocatalytic process over two dimensional (2D) ultrathin nanomaterial is one of the most paramount technologies for solving these problems. In this review, we begin with a brief introduction of five nonmetal-based 2D ultrathin nanomaterials (including black phosphorus (BP), hexagonal boron nitride (h-BN), covalent organic frameworks (COFs), graphene, and polymeric graphitic carbon nitride (g-C 3 N 4)), which mainly discusses the special characteristics of these materials. And then, as the main content of the article, recent advances of optimizing strategies for these five 2D materials are reviewed from the aspects of element doping and construction of heterojunction. We subsequently discuss the new strategies that may be effective for future optimization. Furthermore, the applications of nonmetal-based 2D photocatalysts in energy such as H 2 evolution, CO 2 reduction, N 2 fixation, O 2 evolution, and O 2 reduction are concluded. Finally, conclusions and outlooks are given for future potential directions. [ABSTRACT FROM AUTHOR]

• The roles of biochar in resource recovery from water are overviewed. • Resource recovery of components, water, and energy using biochar are discussed. • Efficiency enhancement strategies for resource recovery by biochar are evaluated. • The value and practical re-application of recovered resources are summarized. • The developments of biochar-based resource recovery are proposed. Over the past few decades, the shortage of water resource has prompted a shift in human concept about waste water: from waste to valuable resource. Utilizing wastewater can not only mitigate water scarcity, but also provide an opportunity for nutrient and energy recovery, further offsetting part of the exploitation of valuable resources. When establishing resource recovery systems of wastewater, the implemented technology and materials should be preferentially considered in order to achieve economically feasible and environmentally responsible solutions. The advantages of biochar in cost, nutrient retention and pollutant adsorption efficiency endow its possibility for resource recovery. Thus, understanding the relationship between biochar and resource recovery is essential to develop the applications of biochar in environment remediation and wastewater utilization. However, to this date there is no comprehensive review that establish the relevance between biochar and recycled substance. In this review, we aim to evaluate the roles of biochar in resource recovery from wastewater. Recyclable substances with the presence of biochar mainly include components, water resource and energy. Viable and effective methods for different recovered targets are classified. In particular, through revealing the interrelationship between biochar production methods and recovered substances, we try to provide the guideline for biochar selection. The re-application and value of recovered substances are also summarized comprehensively. Moreover, the current problems, existing limitations, and promising industrial application value of biochar in resource recovery from water are also put forward. This review can create awareness about the possibility of various options for resources recovery from water with biochar and contribute to further development and demonstration in wastewater treatment. [ABSTRACT FROM AUTHOR]

• FeOOH QDs/CQDs/g-C 3 N 4 0D/2D heterojunction has been first prepared. • 0D/2D heterojunction can realize H 2 O 2 generation and in-situ decomposition. • The composite has excellent charge carrier transfer and separation efficiency. • The introduction of CQDs can improve the photoconversion efficiency. • The generated Fe2+ in FeOOH QDs can promote H 2 O 2 in-situ decomposition. Hydrogen peroxide (H 2 O 2) was generally considered as an ideal energy carrier and environment-friendly oxidant to process environmental modification. Here, FeOOH QDs and CQDs was interspersed on g-C 3 N 4 ultrathin nanosheet to promote H 2 O 2 generation and in-situ decomposition. FeOOH QDs/CQDs/g-C 3 N 4 composite (FCCN) exhibited excellent photoactivity for degrading oxytetracycline (OTC) under visible light illumination. The accelerated photoactivity is ascribed to the following merits: 1) the exciton dissociation interface and carrier transfer channel are fabricated to facilitate photoexcited electron transfer; 2) the photoexcited electron can be rapidly utilized by molecular oxygen to generate H 2 O 2 , resulting in facilitated molecular oxygen activation; 3) Fe3+ in FeOOH QDs is reduced to Fe2+ by photoexcited electron, and then reacts with generated H 2 O 2 to produce OH, thereby promoting photodegradation efficiency. The H 2 O 2 generation yield of FCCN-2 composite was 224.24 µmol h−1 g−1, which was higher than that of pure g-C 3 N 4. 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation and O 2 − quantitative determination displayed outstanding molecular oxygen activation capacity of hybrid composite. Moreover, 0D/2D heterojunction photocatalyst displayed weakened charge carrier recombination efficiency (0.0015 s−1) and expedited surface carrier transfer efficiency (41.01%) compared to g-C 3 N 4 and CQDs/g-C 3 N 4 photocatalyst. Finally, the photodegradation mechanism were rationally evaluated based on the experiment results. [ABSTRACT FROM AUTHOR]