Active chlorine production in concentrated brine is the most mature industrial electrolysis reaction. However, the chlorine evolution reaction (CER) suffers from poor selectivity due to the competing oxygen evolution reaction (OER), particularly in low-concentration chloride and high pH electrolyte. Here, an isolated site engineering strategy is proposed to improve CER selectivity by introducing a hard acid (HA) site to capture OER intermediates (OH*), thereby suppressing their competition with chloride adsorption at CER active sites. A silicon (Si)-doped PtRu catalyst was engineered via discontinuous, spatially separated incorporation, providing isolated Si sites that modulate the local coordination environment. Operando characterizations reveal that Si preferentially binds OER intermediates (OH*), while PtRu binds CER intermediates (Cl*). Electrochemical tests confirm that isolated Si sites suppress oxygenated intermediates (OH*) accumulation on PtRu active sites. Compared with PtRu, PtRuSi shows an enhanced Cl* desorption peak and a reduced OH* desorption peak during CER, along with a weaker methanol probe response in 0.5 M sulfuric acid during methanol oxidation reaction (MOR). Furthermore, the incorporation of Si modulates the catalyst interface, promoting efficient transfer of intermediates from OCl* to Cl*, thereby enhancing CER selectivity. Unlike conventional CER catalysts that are used in acidic electrolytes with highly concentrated sodium chloride (NaCl) (4-6 M), PtRuSi achieved nearly 100% CER selectivity in a low-concentration chloride electrolyte (1.5 M NaCl) under room temperature. Notably, PtRuSi delivered an average CER selectivity of 69.1% in natural seawater (pH 8.2), which was twice that of its PtRu counterpart.

Polyfluoroalkyl compounds like PFOA are of concern due to their widespread use and toxicological risks. nZVI coated with carboxymethyl-beta-cyclodextrin polymer (nFe-CMBCD) showed strong PFOA reduction, reaching 98% at 0.2 and 2 mg L-1 in 5 min, and 90% at 500 mg L-1 in 60 min. Degradation products (acetate, formate, perfluoroheptanoic and perfluorohexanoic acids) suggest chain shortening (C8 -> C7 -> C6). CMBCD likely enhances adsorption on nZVI and electron transfer, enabling conversion to less harmful substances. To the best of our knowledge, this is the first report demonstrating the successful PFOA degradation using nZVI coated with a supramolecular compound under standard conditions.

A solvent-free conversion of graphite into highly porous materials suitable for removal of a broad range of volatile organic compounds (VOCs) is presented. Here we introduce a simple, versatile mechanochemical method, coupled with one-step activation, to prepare porous graphene-containing materials with high yields and porosity. These sorbents exhibited strong efficiency in capturing VOCs, including benzene, hexane, isopropanol, and acetone. The highest adsorption capacity toward the VOCs studied showed a graphene-containing sample activated with potassium carbonate, having specific surface area of 1278 m2/g and total pore volume of 2.34 cm3/g. Thanks to the preserved morphology with graphene domains and large mesopore volume, the sample adsorbed high amounts of various VOCs, including 15.20 mmol/g of benzene, 8.52 mmol/g of toluene, 10.84 mmol/g of styrene, 7.89 mmol/g of hexane, 11.95 mmol/g of isopropanol, and 11.92 mmol/g of acetone at 20 °C and a relative pressure of 0.95 (0.90 for isopropanol). This study examines adsorption of a set of VOCs under identical measurement conditions using a fully automated apparatus, which allows comparison of the adsorption performance of several porous carbons across a broad range of compounds and thus enables the establishment of meaningful structure–property relationships.

A facile synthesis was used for the preparation of highly porous carbons from bread waste. This synthesis relied on the fast ball milling of only two reagents, dry bread, and a mild activation agent, followed by direct thermal treatment at 800°C, afforded carbons with high specific surface areas up to 2400 m2·g-1, and a large pore volume up to 1.56 cm3·g-1. This seems to be the first attempt to employ ball milling for the synthesis of sustainable bread-derived highly porous carbons. Effective activation was achieved thanks to homogeneous distribution of the activating agent throughout the precursor, ensured by mechanochemical treatment. These carbons adsorbed a high amount of carbon dioxide at 0°C and 1 bar, up to 6.7 mmol·g-1. Moreover, cyclic stability, CO2/N2 selectivity at 0°C, and benzene adsorption-desorption isotherms at 20°C were determined for the selected samples. High porosity in carbons is essential for adsorption and catalysis-related applications. Additionally, the proposed strategy provides a solution for cost-effective and feasible food waste management.

A facile mechanochemical synthesis was used for the preparation of mesoporous carbons with large uniform mesopores. The one-pot synthesis relied on the fast ball milling of only two reagents, tannins, and silica colloids, within 10 min, followed by direct thermal treatment at 750 degrees C leading to carbons with uniform mesopores of about 25 nm, high specific surface areas up to -1000 m2/g, and total pore volumes up to 2.80 cm3/g. This seems to be the first attempt to employ mechanochemistry for the synthesis of colloid-imprinted carbons. Moreover, the procedure can be easily extended for the synthesis of carbons with bimodal mesoporosity by adding a Pluronictype soft template to the milling system. The latter synthesis afforded carbons with bimodal mesoporosity, having predominantly pore sizes of 13.8 and 24.8 nm, a high specific surface area of 1218 m2/g, and an exceptionally high pore volume of 4.75 cm3/g, without using an activating agent. To the best of our knowledge, this sample adsorbed a record amount of benzene at 20 degrees C, namely 48.0 mmol/g (375 wt%). It is shown that the total pore volume is a determining factor for benzene adsorption on diverse porous solids. High mesoporosity in carbons might be essential in adsorption and catalysis-related applications.

Semiconductor photocatalysts hold great potential for sustainable energy and environmental applications, but optimizing their performance requires understanding of their behavior under working conditions. In situ characterization techniques, enabling observations under light illumination and in the presence of reactants, are essential for capturing dynamic processes during photocatalysis. This review highlights the application of in situ methods, including X-ray photoelectron spectroscopy and X-ray absorption spectroscopy for monitoring oxidation states; Raman and infrared spectroscopy for analyzing chemical bonds and groups; electron spin resonance spectroscopy and total internal reflection fluorescence microscopy for studying unpaired charge carriers and radicals; photoluminescence, infrared spectroscopy and transient absorption spectroscopy for probing charge excitation and relaxation. These techniques have been employed to examine structural and compositional transformations, such as photocorrosion, metal species reduction and oxidation, and lattice oxygen loss; detect surface intermediates; investigate charge dynamics, such as charge separation and trapping; and identify active sites, including vacancies, metal-based sites, molecular sites, and active components in heterojunctions. The review concludes by discussing challenges and opportunities, specifically, the replication of ambient reaction conditions, mitigation of interference from light sources during spectroscopic measurements, exploration of morphological changes in semiconductors during photocatalysis, and understanding of the effects of photocatalysis on band bending at interfaces.

Conventional methods for the synthesis of porous carbons are typically time- and energy-consuming and often contribute to the excessive accumulation of waste solvents. An alternative approach is to employ environmentally friendly procedures, such as mechanochemical synthesis, which holds great potential for large-scale production of advanced carbon-based materials in coming years. This review covers mechanochemical syntheses of highly porous carbons, with a particular focus on new adsorbents and catalysts that can be obtained from biomass. Mechanochemically assisted methods are well suited for producing highly porous carbons (e.g., ordered mesoporous carbons, hierarchical porous carbons, porous carbon fibers, and carbon–metal composites) from tannins, lignin, cellulose, coconut shells, nutshells, bamboo waste, dried flowers, and many other low-cost biomass wastes. Most mechanochemically prepared porous carbons are proposed for applications related to adsorption, catalysis, and energy storage. This review aims to offer researchers insights into the potential utilization of biowastes, facilitating the development of cost-effective strategies for the production of porous carbons that meet industrial demands.

Aqueous batteries (ABs) are considered emerging candidates for grid‐scale energy storage due to their inherent safety, cost‐effectiveness, and environmental compatibility. In recent years, major advances have been made in ABs toward improving their energy density and cycling stability, and progressing their prospects for real application. However, self‐discharge, a critical parameter for practical applications, remains largely underexplored. Many studies either overlook this aspect entirely or employ inconsistent testing protocols, making cross‐system comparisons difficult and diminishing the reliability of reported data. To date, no comprehensive review that systematically addresses self‐discharge in ABs is available. In this review, we aim to fill this gap by providing an in‐depth analysis of self‐discharge phenomena in state‐of‐the‐art ABs. We first summarize the underlying mechanisms responsible for self‐discharge and then critically evaluate current measurement approaches, offering recommendations for practical and standardized testing protocols. Furthermore, we highlight mitigation strategies from both electrolyte and electrode perspectives, providing a materials‐oriented overview of self‐discharge suppression. This review not only offers a theoretical framework for understanding self‐discharge behaviors in ABs, but also proposes clear guidelines for future experimental assessment, thereby enhancing their practical relevance and accelerating their development toward commercialization.

Solvothermal synthesis of zirconia decorated with vanadium oxide is investigated with the aim of using it in the catalytic conversion of nitrogen oxides. The effect of the mass ratio of vanadium (1.9; 3.8 and 5.7 wt%) to pure zirconia on the physicochemical and catalytic properties of the fabricated materials is demonstrated. The physicochemical characterization of catalysts indicates a slight reduction in the size of particles as well as an improvement in the textural properties with increasing mass of vanadium. The X-Ray diffraction analysis proves that the introduction of vanadium precursor inhibits crystallization of monoclinic zirconia and leads to the formation of different vanadium oxide moieties. The reported data on the selective catalytic reduction prove that zirconia catalysts decorated with vanadium mass ratio of 3.8 wt% and 5.7 wt% achieved the highest conversion of nitrogen oxides, reaching 80 % in the temperature range 480-520 degrees C. The obtained results suggest that in the fabricated catalysts, V2O5 species are the main active sites for the SCR-NH3 reaction process.

Urea electrooxidation offers a cost-effective alternative to water oxidation for energy-saving hydrogen production. However, its practical application is limited by expensive urea reactants and sluggish reaction kinetics. Here, we present an efficient urine electrolysis system for hydrogen production, using cost-free urine as feedstock. Our system leverages a discovered Cl-mediated urea oxidation mechanism on Pt catalysts, where adsorbed Cl directly couple with urea to form N-chlorourea intermediates, which are then converted into N2 via intermolecular N–N coupling. This rapid mediated-oxidation process notably improves the activity and stability of urine electrolysis while avoiding Cl-induced corrosion, enabling over 200 hours of operation at reduced voltages. Accordingly, a notable reduction in the electricity consumption is achieved during urine electrolysis (4.05 kWh Nm−3) at 300 mA cm−2 in practical electrolyser for hydrogen production, outperforming the traditional urea (5.62 kWh Nm−3) and water (4.70–5.00 kWh Nm−3) electrolysis. Urea electrooxidation offers an energy-saving route for hydrogen production but faces challenges from costly reactants and slow kinetics. Here, the authors introduce a chlorine-mediated electrolysis system using natural urine as feedstock, achieving enhanced and cost-effective hydrogen production.

Aqueous zinc-iodine (Zn-I-2) batteries, leveraging abundant resources and inherent safety, face commercialization challenges due to low cathode loading and iodine sublimation in traditional fabrication methods. We introduce a dry electrode preparation technique that significantly enhances the areal capacity to 15.8 mA h cm(-2) (ZnI2 loading >100 mg cm(-2)), far exceeding previous Zn-I-2 and commercial Li-ion batteries (similar to 3-5 mA h cm(-2)). This method not only increases cathode loading but also reduces polyiodides' shuttle effects and self-discharge rates, achieving a low discharge rate of 11.16% over 168 h. To address zinc-related issues at high loadings, 1,3,5-trioxane is added to the electrolyte to form a flexible polymer solid electrolyte interphase, preventing zinc dendrite formation. Our approach enables an A h-level pouch cell with remarkable cycling stability, maintaining 88.6% capacity after 750 cycles at 1 C at a high areal capacity of 15.8 mA h cm(-2), demonstrating potential applicability to other aqueous and halogen-based battery systems.

Anion-exchange-membrane water electrolysis (AEMWE) is a promising technology for scalable green hydrogen production. However, the conventional use of high-alkalinity conditions accelerates membrane degradation, emphasizing the need for low-alkalinity operation to ensure long-term stability. For a low-alkalinity electrolyte with a high water-dissociation energy barrier, Ru serves as an ideal cathodic catalyst owing to its strong Ru-H bond, which provides distinguished water dissociation ability. However, the trade-off is high *H coverage, causing sluggish kinetics and limited durability during high-current operation. Herein, we developed an Ir-Ru solid solution catalyst, which enables rapid hydrogen transfer kinetics through a hydrogen spillover mechanism at high current. As a result, AEMWE with the Ir-Ru solid solution achieved a cell voltage of 1.75 V at 1 A cm-2 in 0.05 M KOH. Notably, the low-alkalinity AEMWE cell exhibited exceptional durability for over 1000 h, surpassing most of the previously reported data under similar operating conditions. Isotope labeling and in situ characterizations confirmed that dissociated *H spills from efficient water-dissociation sites on Ru to favorable hydrogen-desorption sites on Ir with lower *H coverage, significantly improving activity and stability at high current densities.

Conventional acidic electrolytes for the electrochemical CO2 reduction reaction normally require highly concentrated alkali-metal cations (i.e., K+). However, the usage of high [K+] generally induces a fast pH increase in the catholyte during CO2 electrolysis, thereby leading to an unstable system and frequent electrolyte refreshing. In this work, ultralow-concentrated (alkyl)ammonium-based cations are rationally developed to enable efficient metal-cation-free CO2 electroreduction in strong acids. Compared with traditional K+, the NH4+ cation possesses a higher positively charged center, lower hydration number, and larger surface charge density, leading to significantly lower local pK(a) (acid dissociation constant). This low local pK(a) results in a higher percentage of free water that provides sufficient absorbed *H for the hydrogenation of *CO2 to form *COOH (the key intermediate of the CO pathway). As a result, ultradiluted (0.05 M) NH4+ cations added to strong sulfuric acid (bulk pH 1.1) with silver nanoparticles used as catalysts display a substantially higher Faradaic efficiency and partial current density of the CO product than the traditional K+-based electrolyte under the same electrolysis conditions. Moreover, it also shows a substantially lower pH change rate in the catholyte compared with a highly concentrated (3 M) K+-based one during an entire refreshing cycle, leading to a more stable electrolyte system.

An ever-increasing demand for graphene and its derivatives in recent years has stimulated research toward developing simple, accessible, and effective methods for the fabrication of graphene-based materials. Mechanochemical exfoliation of graphite powder is one of the simplest and most cost-effective methods to obtain graphene-containing materials. However, the limited availability and price of commercial graphite hinder their large-scale production. Here we propose a simple and versatile mechanochemical method for exfoliation of various graphite-based wastes, i.e., graphite electrodes, graphite analytical crucibles, graphite brushes, and graphite from pencils, to produce graphene-based materials with high yield and specific surface areas up to ~ 530 m 2 /g. The as-prepared porous materials can serve as adsorbents for CO 2 , exhibiting a capacity of 1.9 mmol/g at 0 °C and 1 bar. This method provides an alternative for reusing graphite waste by converting it into porous materials that are attractive for diverse applications, including adsorption and catalysis. The proposed strategy increases the availability of graphene-containing materials and provides a solution for cost-effective and feasible graphite waste management. Graphical Abstract

Electrolysis of low-grade impure water offers a sustainable approach to hydrogen production. However, unstable interfacial pH caused by electrochemical reactions accelerates ion-induced electrode degradation. Here, we show an ion-selective gate strategy, in which ion-conducting polymer coatings are applied onto commercial platinum carbon and iridium oxide catalysts to enable selective ion transport and to stabilize the interfacial pH. Compared with conventional aqueous electrolytes, this solid-state configuration effectively suppresses local pH fluctuations and blocks the migration of detrimental impurity ions. The ion-selective gate achieves nearly complete rejection of common ions found in seawater, river and lake water, and industrial wastewater, demonstrating broad adaptability to impurity-rich environments. In untreated seawater, the ion-selective gate engineered electrode operates stably for 1500 h at 200 mA cm-2, with a degradation rate of 5.2 mV kh-1, approaching the durability of pure water electrolysis. This design is compatible with both proton exchange membrane and anion exchange membrane electrolyzers, providing a scalable route for sustainable hydrogen generation from natural water sources.

Titanium dioxide nanoparticles (TiO2 NPs) have traditionally been utilized as industrial catalysts, finding widespread application in various chemical processes due to their exceptional stability and minimal toxicity. However, quantitatively assessing the reactive sites on TiO2 NPs remains a challenge. In this study, we employed a fluorogenic reaction to probe the apparent reactivity of TiO2 NPs. By manipulating the number of defect sites through control of hydrolysis speed and annealing temperature, we determined that the Ti(III) content is positively correlated with the reactivity of TiO2 NPs. Additionally, these Ti(III) sites could be introduced by reducing commercial TiO2 NPs using NaBH4. Our findings suggest that fluorogenic oxidation of Amplex Red is an effective method for probing defect site densities on TiO2 NPs. Utilizing single-molecule fluorescence imaging, we demonstrated the ability to map defect site density within TiO2 nanowires. Achieving sub-nanoparticle spatial resolution, we observed significant intraparticle and interparticle variations in the defect site distribution, leading to substantial reactivity heterogeneity. Defect site-rich titanium dioxide promotes the activation of hydrogen peroxide generating more reactive oxidative species and exhibits outstanding advantages on chemical oxidation. The cycle of Ti(III) and Ti(IV) plays an important role in the catalytic enhancement. More importantly, single-molecule catalysis has great potential to avoid the heterogeneity of nanocatalysts and probe the defect site distributions. image

A simple, green, and relatively fast procedure was used to prepare palladium decorated graphene-based materials. A parent graphene-like material with a high specific surface area of up to 384 m2 /g and a total pore volume of 0.42 cm3 /g was prepared via a fast, solvent-free ball milling of graphite powder only. Post-synthetic modification of this graphene-like material was performed via a simplified method using palladium chloride and a small amount of a non-harsh reducing agent - formic acid. Palladium decoration (2.1 wt%) allowed obtaining a few times higher hydrogen adsorption (0.42 wt% at 30 °C and 40 bar) compared to that on bare graphene-based materials. Palladium-decorated graphene materials are promising for hydrogen storage and their usage in this application represents an alternative for conventional fossil fuels. The proposed synthesis and post-modification strategies are in line with green synthesis strategies.

The electrochemical CO2 reduction reaction (CO2RR) is of great importance to produce valuable chemicals. In conventional alkaline and "acid + salts"-based CO2RR, the aqueous electrolyte normally needs to be refreshed due to the gradually more neutral feature of pH during electrolysis operation. Therefore, both solutes and deionized (DI) water in electrolytes are required to be regenerated regularly. In this work, acidic seawater (pH < 2) was used as a low-cost but efficient electrolyte for CO2RR without salt addition. The Faradaic efficiencies (FEs) and partial current densities of C2+ on typical copper in the "H2SO4 in raw seawater" electrolyte are comparable with those for conventional "KOH in DI water" and much higher than those for "H2SO4 + salts" systems. Moreover, single-pass carbon efficiencies (SPCEs) in acidic seawater are significantly higher than the values in alkaline DI water. Such an abnormal phenomenon was also demonstrated for CO and HCOOH generation on typical silver and tin catalysts, respectively. In situ Raman spectroscopy and controlled experiments revealed that metal (denoted as M) cations in seawater ensure a higher concentration of MH2O species, which improve interactions with *CO2 -, while Cl- anions enhance the adsorption strength of key CO2RR intermediates (namely, *CO on copper, *COO- on silver, and *OCHO on tin). Through these interactions with water molecules and CO2RR intermediates, such free but functional ions in seawater play a highly important role in promoting selectivity and activity for CO2RR, as well as SPCE in acidic seawater. Furthermore, using acidic seawater as an alternative CO2RR electrolyte has significant economic and ecological benefits compared with traditional alkaline DI water electrolytes.

Over the last decade, carbon-based metal-free electrocatalysts (C-MFECs) have become important in electrocatalysis. This field is started thanks to the initial discovery that nitrogen atom doped carbon can function as a metal-free electrode in alkaline fuel cells. A wide variety of metal-free carbon nanomaterials, including 0D carbon dots, 1D carbon nanotubes, 2D graphene, and 3D porous carbons, has demonstrated high electrocatalytic performance across a variety of applications. These include clean energy generation and storage, green chemistry, and environmental remediation. The wide applicability of C-MFECs is facilitated by effective synthetic approaches, e.g., heteroatom doping, and physical/chemical modification. These methods enable the creation of catalysts with electrocatalytic properties useful for sustainable energy transformation and storage (e.g., fuel cells, Zn-air batteries, Li-O2 batteries, dye-sensitized solar cells), green chemical production (e.g., H2O2, NH3, and urea), and environmental remediation (e.g., wastewater treatment, and CO2 conversion). Furthermore, significant advances in the theoretical study of C-MFECs via advanced computational modeling and machine learning techniques have been achieved, revealing the charge transfer mechanism for rational design and development of highly efficient catalysts. This review offers a timely overview of recent progress in the development of C-MFECs, addressing material syntheses, theoretical advances, potential applications, challenges and future directions.