Bifunctional Materials Research Articles

Imidazolium-Functionalized Conjugated Polymer for On-Site Visual and Ultrasensitive Detection of Toxic Hexavalent Chromium.

Hexavalent chromium [Cr(VI)] is considered a serious environmental pollutant that possesses a hazardous effect on humans even at low concentrations. Thus, the development of a bifunctional material for ultratrace-selective detection and effective elimination of Cr(VI) from the environment remains highly desirable and scarcely reported. In this work, we explore an imidazolium-appended polyfluorene derivative PF-DBT-Im as a highly sensitive/selective optical probe and a smart adsorbent for Cr(VI) ions with an ultralow detection limit of 1.77 nM and removal efficiency up to 93.7%. In an aqueous medium, PF-DBT-Im displays obvious transformation in its emission color from blue to magenta on exclusively introducing Cr(VI), facilitating naked-eye colorimetric detection. Consequently, a portable sensory device integrated with a smartphone is fabricated for realizing real-time and on-site visual detection of Cr(VI). Besides, the imidazolium groups attached onto side chains of PF-DBT-Im are found to be highly beneficial for achieving selective and efficient elimination of Cr(VI) with capacity as high as 128.71 mg g-1. More interestingly, PF-DBT-Im could be easily regenerated following treatment with KBr and can be recycled at least five times in a row. The main factor behind ultrasensitive response and excellent removal efficiency is found to be anion-exchange-induced formation of a unique ground-state complex between PF-DBT-Im and Cr(VI), as evident by FT-IR, XPS, and simulation studies. Thus, taking advantage of the excellent signal amplification property and rich ion-exchange sites, a dual-functional-conjugated polymer PF-DBT-Im is presented for the concurrent recognition and elimination of Cr(VI) ions proficiently and promptly with great prospects in environmental monitoring and water decontamination.

Solar thermo-photocatalytic methanation using a bifunctional RuO2:TiO2/Z13X photocatalyst/adsorbent material for efficient CO2 capture and conversion

A novel bifunctional photocatalyst/adsorbent material based on the RuO2:TiO2/zeolite 13X (Z13X) composite was developed to enhance solar-driven methanation through simultaneous carbon dioxide (CO2) capture and thermo-photoconversion. The activity/stability of the hybrid material towards methane (CH4) production was assessed by varying the (i) photocatalyst composition (Ru load and semiconductor type), (ii) bifunctional material composition (photocatalyst-to-zeolite ratio) and impregnation method, (iii) illumination source and power (simulated sunlight and UVA/Visible LEDs), (iv) temperature, and (v) catalyst reuse. Additionally, adsorption equilibrium isotherms were determined to characterize the adsorption ability of the bifunctional material for both CO2 and CH4 gases. The hybrid RuO2(4.0%):TiO2(26.3%)/Z13X material (30 mg), synthesised by the solid-state impregnation method, showed the best results under simulated sunlight (0.75 W) at 150 ºC, achieving a 88% CO2 thermo-photoreduction after 100 min, corresponding to a specific CH4 production of 29.2 mmol gactive_cat−1 h−1 (309 mmol gRu−1 h−1) and apparent quantum yield of 20.7%. In adsorption equilibrium isotherms, the bifunctional material's adsorption was about 2.6-fold higher than the photocatalyst at 150 ºC, suggesting that enhanced methanation performance can be attributed to the synergistic action of CO2 capture and thermo-photoconversion.

Highly Crystalline Iridium-Nickel Nanocages with Subnanopores for Acidic Bifunctional Water Splitting Electrolysis.

Developing efficient bifunctional materials is highly desirable for overall proton membrane water splitting. However, the design of iridium materials with high overall acidic water splitting activity and durability, as well as an in-depth understanding of the catalytic mechanism, is challenging. Herein, we successfully developed subnanoporous Ir3Ni ultrathin nanocages with high crystallinity as bifunctional materials for acidic water splitting. The subnanoporous shell enables Ir3Ni NCs optimized exposure of active sites. Importantly, the nickel incorporation contributes to the favorable thermodynamics of the electrocatalysis of the OER after surface reconstruction and optimized hydrogen adsorption free energy in HER electrocatalysis, which induce enhanced intrinsic activity of the acidic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Together, the Ir3Ni nanocages achieve 3.72 A/mgIr(η=350mV) and 4.47 A/mgIr(η=40mV) OER and HER mass activity, which are 18.8 times and 3.3 times higher than that of commercial IrO2 and Pt, respectively. In addition, their highly crystalline identity ensures a robust nanostructure, enabling good catalytic durability during the oxygen evolution reaction after surface oxidation. This work provides a new revenue toward the structural design and insightful understanding of metal alloy catalytic mechanisms for the bifunctional acidic water splitting electrocatalysis.

Synthesis Design and Properties of Ca5(BO3)3F: Bi3+/Eu3+: Insight into Luminescence, Temperature, and Pressure Sensing.

Nowadays, the utilization of noncontact temperature and pressure sensing is experiencing growing popularity. In this work, Bi3+, Eu3+-doped Ca5(BO3)3F (CBOF) phosphors were synthesized via an ionic liquid-assisted electrospinning approach. The effect of molecular weight of polyvinylpyrrolidone on the morphology of CBOF was investigated, and a comprehensive analysis of its formation mechanism was presented. The luminescence properties of CBOF: Bi3+, Eu3+ were studied systematically. The temperature-dependent emission of CBOF: Bi3+, Eu3+ phosphor was discussed, and it displayed thermal sensitivity, which can be attributed to the distinct thermal response emission behaviors of Bi3+ and Eu3+. The investigation of the pressure-dependent emission behavior of the CBOF: Bi3+ phosphor revealed an anomalous phenomenon: with the increase of pressure, the emission peak showed a trend of first a blue shift and then a red shift. This anomaly was discussed in detail. The phosphor exhibits visual color change (blue to cyan), remarkable pressure sensitivity (4.76 nm/GPa), and a high upper pressure limit (24.2 GPa), indicating its potential use as an optical pressure sensor. Consequently, this study presents an innovative synthetic approach for fabricating CBOF, presenting a bifunctional material with promising prospects in the fields of temperature and pressure sensing.

A novel readily recyclable Fe3O4/ZnO/loofah biochar composite for efficient degradation of organic pollutants under visible light

A recyclable magnetic bifunctional biochar photocatalyst material (FZLB) comprising of Fe3O4/ZnO/ Lufa-biochar was developed for the efficient degradation of phenols found in mechanical wastewater. The use of filamentous biochar not only provided abundant open active sites essential for the photocatalytic reaction, but also facilitated mass transfer, amplified the charge transfer rate and reduced the complexation of photogenerated electron-hole pairs. Of the catalysts tested, the 20 % FZLB catalyst demonstrated the greatest photocatalytic activity, achieving 96.5 % phenol degradation following 90 min of visible light exposure alone. Notably, the material could be quickly retrieved in 90 s, making it highly efficient for use in managing mechanical wastewater when visible light is present. The 20 % FZLB catalyst's notable photocatalytic activity highlights its potential as a viable solution for effective mechanical wastewater management under visible light conditions.

Ni-CaO-CaZrO3 bi-functional materials for high purity hydrogen production via sorption enhanced steam reforming of ethanol

Ethanol is an ideal hydrogen carrier, which can be converted to hydrogen-rich syn-gas via the steam reforming reaction. Sorption-enhanced steam reforming is a promising approach to produce high-purity hydrogen by mixing the sorbent and catalyst particles. The idea of bi-functional materials, loading both sorption and catalytic site in a single particle, could transform the inter-particle heat-mass transfer to intra-particle heat-mass transfer. This work studied the sorption-enhanced steam reforming of ethanol (SESRE) over Ni-CaO-CaZrO3 bi-functional catalysts containing sorption and catalytic sites. Bi-functional Ni-CaO-CaZrO3 catalysts were synthesized using a simple sol-gel technique. The influence of operating conditions including temperature, steam-to-carbon ratio (S/C) and weight hourly space velocity (WHSV) on Ni10-Ca90Zr10 bi-functional materials were discussed. The operating condition with a temperature of 600 °C, weight hourly space velocity of 0.34 h−1 and steam-to-carbon ratio of 3 was the most suitable reaction condition for hydrogen production in this study. Over the optimized operation conditions, the influence of Ni loadings on hydrogen production performance was further studied. The result indicated that 10 wt% is the best Ni loading in this study for Ni-CaO-CaZrO3, which enables >95% hydrogen purity in the gaseous product in the pre-breakthrough stage, with the longest breakthrough time (90 min). Furthermore, under the best operation conditions, the Ni10-Ca90Zr10 displayed excellent stability over 10 cyclic tests. In the 10th cycle, about 90% hydrogen purity was constantly obtained for at least 60 min during the pre-breakthrough stages. This study demonstrated that the Ni10-Ca90Zr10 bi-functional material is effective and stable for producing hydrogen from ethanol and has the potential to establish a method of generating clean energy with minimal carbon emission.

Electrochemically Induced Ru/CoOOH Synergistic Catalyst as Bifunctional Electrode Materials for Alkaline Overall Water Splitting.

Efficient and affordable price bifunctional electrocatalysts based on transition metal oxides for oxygen and hydrogen evolution reactions have a balanced efficiency, but it remains a significant challenge to control their activity and durability. Herein, a trace Ru (0.74 wt.%) decorated ultrathin CoOOH nanosheets (≈4 nm) supported on the surface of nickel foam (Ru/CoOOH@NF) is rationally designed via an electrochemically induced strategy to effectively drive the electrolysis of alkaline overall water splitting. The as-synthesized Ru/CoOOH@NF electrocatalysts integrate the advantages of a large number of different HER (Ru nanoclusters) and OER (CoOOH nanosheets) active sites as well as strong in-suit structure stability, thereby exhibiting exceptional catalytic activity. In particular, the ultra-low overpotential of the HER (36mV) and the OER (264mV) are implemented to achieve 10mAcm-2. Experimental and theoretical calculations also reveal that Ru/CoOOH@NF possesses high intrinsic conductivity, which facilitates electron release from H2O and H-OH bond breakage and accelerates electron/mass transfer by regulating the charge distribution. This work provides a new avenue for the rational design of low-cost and high-activity bifunctional electrocatalysts for large-scale water-splitting technology and expects to help contribute to the creation of various hybrid electrocatalysts.

Functionalized nanocellulose as a bifunctional material for efficient adsorption of mercuric ions with antimicrobial properties

AbstractTo develop a green nanomaterial for specialty applications, spherical nanocellulose (SNC) was functionalized to a semicarbazone‐Schiff base via a polymer analogous reaction. Firstly, SNC was synthesized from cellulose extracted from huge forest biomass, pine needles (PNs). The glucopyranose ring of SNC was oxidatively cleaved at C2–C3 to form SNC‐dialdehyde (SNC‐DA) by periodate oxidation. Both the aldehydic groups generated were reacted with semicarbazide to form a semicarbazone‐Schiff base, referred to as functional spherical nanocellulose (FSNC). All the materials synthesized were characterized by FTIR, FESEM, EDS, TEM, and XRD studies. The FSNC was evaluated as an adsorbent for Hg2+ ions. The adsorption adhered to pseudo‐second order kinetics and Langmuir adsorption isotherm having a maximum adsorption capacity/Lungmuir adsorption capacity of 172.412 mg/g at 60 min. The selectivity of FSNC for Hg2+ ions was confirmed from its appreciable removal (82%) from solution in tap water and 70% with other metal ions. FSNC exhibited bifunctional nature as it possesses antimicrobial activity against bacteria, that is, Gram (+) (Bacillus aereus) and Gram (−) (Escherichia coli and Salmonella typhi), and a fungus Byssochlamys fulva. FSNC showed good recyclability up to eight sorption–desorption cycles. Thus, we have valorized biomass into an eco‐friendly and low‐cost bifunctional material as an adsorbent for Hg2+ ions cum antimicrobial agent.Highlights Spherical nanocellulose (SNC) prepared via acidic hydrolysis from pine needles SNC functionalized to semicarbazone‐based bifunctional Schiff base The Schiff base is a rapid and efficient Hg2+ ions adsorbent The Schiff base has good antimicrobial activities against Gram (−) bacteria Biowaste‐based adsorbent has the potential to sustain the bio‐circular economy

A bifunctional Zn(II) coordination polymer for fluorescence recognition towards hazardous matters and its high adsorption removal of dye pollutant

In this work, a novel Zn(II) coordination polymer (denoted as Zn-CP) was constructed by the mixed ligands of 6-(3′,4′-Dicarboxy phenoxy)isophthalic acid (H4L) and 4,4′-bis(imidazolyl)biphenyl (bib) under solvothermal method. And based on the Zn-CP, the surfactant agent sodium dodecyl sulfate (SDS) was further introduced into the structure, thus obtaining the Zn-CP(S) which possessed the same phase but a smaller size compared with the Zn-CP. Interestingly, the Zn-CP(S) presented a significantly ameliorated fluorescent intensity, about 4.36 times higher than that of the Zn-CP prepared in the absence of SDS. Taking advantage of the improved fluorescence trait of the Zn-CP(S), a fluorescence recognition towards hazardous matters was further carried out. The results showed that Zn-CP(S) could simultaneously recognized for Hg2+, Cr2O72− and a broad range of hazard nitroaromatic explosives with the satisfactory limits of detection (LODs). In addition, Zn-CP could also be used as a recyclable adsorbent to remove methyl orange (MO) in aqueous medium. The maximum equilibrium adsorption capacity of Zn-CP for MO was 61.01 mg/g, and the adsorption mechanism could be attributed to the weak inter-molecular interaction involved π-π stacking and hydrogen bonding between Zn-CP and the MO molecule. Therefore, the bifunctional material has potential application prospects in fluorescence recognition and adsorption.

Optimizing Oxygen Electrode Bifunctionality with Platinum and Nickel Nanoparticle-Decorated Nitrogen-Doped Binary Metal Oxides

Developing bifunctional oxygen electrode materials with superior activity for oxygen reduction (ORR) and oxygen evolution (OER) reactions is essential for advancing regenerative fuel cell and rechargeable metal–air battery technologies. This present work deals with the synthesis and characterization of electrocatalysts containing Pt and Ni nanoparticles supported on nitrogen-doped mixed metal oxides (Mn2O3-NiO) and the systematic evaluation of their bifunctional ORR/OER performance in an alkaline medium. These electrocatalysts have been successfully synthesized by a simple and fast microwave method. PtNi/Mn2O3-NiO-N with a binary metal oxide-to-N ratio of 1:2 demonstrated the best performance among the studied materials regarding bifunctional electrocatalytic activity (∆E = 0.96 V) and robust stability.

Reduction-orientated selective removal of selenate by thiourea-functionalized polystyrene material

Efficient removal of trace selenate [Se(VI)] from contaminated water is still challenging because of the inevitable interference from the coexisting anions toward the adsorption or ion-exchange process. Herein, a bifunctional material (NCS@CMPS) was proposed for selective removal of Se(VI) from a complex matrix. NCS@CMPS was subtly prepared by grafting a chloromethylated polystyrene substrate (CMPS) with thiourea, resulting in reductive groups (C-SH and C=S) and adsorptive sites (–NH-, –NH2, and C=NH2+) anchored on the skeleton of CMPS. Batch studies demonstrated an excellent removal efficiency and anti-interference capabilities of NCS@CMPS toward Se(VI), even with very high levels of competing anions (chloride, sulfate, phosphate, nitrate, and bicarbonate) over a wide pH range (3 ∼11). The in-situ reductive removal and the unique pH-buffering effect of NCS@CMPS were responsible for the high selectivity and the wide applicability. The XPS analyses identified the removal mechanisms of concentrating, reducing, and sequestrating of Se species inside NCS@CMPS, where the majority of Se species was reduced to Se(IV) (80.9%). In column mode, NCS@CMPS can treat over 10,000 bed volumes (BV) of a simulated Se(VI) wastewater ([Se]ini = 200 μg/L) to below 10 μg/L, whereas the capacity of its substrate (i.e., CMPS) was only 28 BV. Additionally, the exhausted NCS@CMPS can be regenerated by NaBH4-NaOH-HCl treatment for repeated use. Moreover, the effectiveness of NCS@CMPS in treating actual industrial Se(VI) wastewater was also validated.

Experimental investigation of integrated CO2 capture and conversion to syngas via calcium looping coupled with dry reforming of CH4

Calcium looping integrated with dry reforming of CH4 is a promising strategy for CO2 capture and in situ conversion to syngas. This intensified process is usually conducted with bifunctional materials that combine CO2 capture (CaO) and catalytic (Ni) active sites. Herein, the integrated calcium looping/dry reforming process was examined by investigating various bifunctional materials and operating conditions. The Ni loading of materials affected the interaction between active and inert phases, while adding a CaZrO3 promoter enhanced the CO2 capture and catalytic activities and the resistance toward sintering. Conducting experiments with a fluidized bed reactor (700 °C, 3% CH4 in feed) led to nearly complete CH4 conversion and ∼52% utilization of captured CO2 toward syngas production with steady H2/CO ratio close to unity. Temperature comprised a decisive parameter, with low values enabling high degrees of CO2 conversion up to ∼80%. The increase of CH4 concentration in the gas feedstock enhanced the rate of calcination and the conversion of CO2 over its desorption in the gas phase. Co-feeding O2 with CH4 was proposed to mitigate the energy demand, which reduced the reforming selectivity for the partial oxidation reaction and increased the H2/CO ratio of syngas.

Bi-functional material SnSSe/rGO with anionic vacancies serves as a polysulfide shuttling blocker and lithium dendrite inhibitor

The notorious polysulfide shutting and the irregular lithium dendrites are the leading causes for hindering lithium-sulfur batteries’ marketization. Herein, a bi-functional material consisting of an anionic vacancy-rich SnSSe layer stacked with graphene (SnSSe/rGO) composite is proposed, which possesses the characteristics of simultaneously immobilizing polysulfides and suppressing dendritic growth. The enhanced sulfiphilicity enables SnSSe/rGO as a separator modification layer (SnSSe/rGO@PP) to effectively adsorb polysulfides and catalyze their rapid conversion. The Li-S half-cell containing SnSSe/rGO@PP exhibits long cycling stability and outstanding rate capacity. Moreover, SnSSe/rGO can regulate lithium deposition behavior due to its strong lithiophilicity and interaction with lithiated products. The lithium anode employing SnSSe/rGO electrode (SnSSe/rGO@Cu-Li) demonstrates low nucleation overpotential and stable plating/stripping cycling. Consequently, the prepared Li-S full cells demonstrate a remarkable area capacity of about 8.0 mAh cm−2, even when subjected to lean electrolyte (9.0 µL mg−1) and low N/P ratio (about 1.3) with high sulfur loading (11.2 mg). This study reveals a fresh perspective for designing efficient bi-functional materials to solve both the shuttle effect and lithium dendrites in high-energy-density Li-S batteries.

Fe-Co-Ni trimetallic Prussian blue analogs with tunable electrochromic energy storage properties

Prussian blue (PB) and its analogs (PBAs) have become a research hotspot in the fields of electrochemical energy storage and electrochromism due to their good reversible redox activity, and reversible color change response in different redox states. Herein, a series of trimetallic PBAs (Co/NiHCF with Co to Ni molar ratios of 1:0, 3:1, 1:1, 1:3, and 0:1) are synthesized by a facile co-precipitation method. In particular, the impact of Co to Ni molar ratio on the lithium storage and electrochromic properties of Co/NiHCF materials are systemically investigated. All five samples possess good crystallinity but the particle size decreases with the reduction of Co/Ni molar ratio. The color change, redox reaction potential, and lithium storage activity of the samples can be readily controlled by adjusting the molar ratio of Co to Ni. The lithium storage activity of the samples strengthens with the increase of Ni content in Co/NiHCF, accompanied by a decrease in redox potentials. With the increase of Ni content, the color of the Co/NiHCF film in the oxidation state changes from purple-red to orange, and finally to yellow; in the reduction state, the color of the film changes from green to light green and then to colorless. All the samples exhibit superior rate capability, excellent cycling stability, and short switching time (in the range of 1.6 to 4.3 s). The present work demonstrates a facile strategy for readily tunning the lithium storage activity, redox reaction potentials, and realizing rich color changes of PBA-based bifunctional materials.

Theoretical investigation on the strain engineering control of TiC as tunable high-efficiency bifunctional cathode materials for Lithium–Sulfur batteries

Developing efficient cathode materials and strategies to suppress the shuttle effect and promote the reaction kinetics were the key scientific issues for the development of high performance lithium–sulfur (Li–S) batteries. Modify the properties of a material through strain engineering is an effective strategy to enhance the performance of adsorption and catalysis ability for special species. In this paper, first-principles calculations were carried out to investigate the anchoring effect and electrochemical performance of TiC (001) subjected to biaxial symmetric mechanical (compressive and tensile) strains. The results demonstrate that the adsorption energies of the lithium polysulfides (LiPSs) were enhanced monotonically and the metallic properties were also remaining along with the strain from compressive to tensile . In addition, an appropriate strain could reduce the migration barrier of Li ions, the dissociation barrier of Li2S and the Gibbs free energy of the sulfur reduction reaction (SRR) to realize the rapid charge/discharge processes. Especially, the p-band center of carbon atoms in TiC was proposed as an effective descriptor to identify the adsorption and catalysis ability of the anchoring materials under biaxial strain. Our results indicate that strain engineering is a promising strategy to improve the comprehensive performance of anchoring materials in Li − S batteries.

Interfacial Electronic Modulation of Mo5N6/Ni3S2 Heterojunction Array Boosts Electrocatalytic Alkaline Overall Water Splitting.

Bifunctional electrocatalysts with excellent activity and durability are highly desirable for alkaline overall water splitting, yet remain a significant challenge. In this contribution, palm-like Mo5N6/Ni3S2 heterojunction arrays anchored in conductive Ni foam (denoted as Mo5N6-Ni3S2 HNPs/NF) are developed. Benefiting from the optimized electronic structure configuration, hierarchical branched structure and abundant heterogeneous interfaces, the as-synthesized Mo5N6-Ni3S2 HNPs/NF electrode exhibits remarkably stable bifunctional electrocatalytic activity in 1m KOH solution. It only requires ultralow overpotentials of 59 and 190mV to deliver a current density of 10mAcm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1m KOH solution, respectively. Importantly, the overall water splitting electrolyzer assembled by Mo5N6-Ni3S2 HNPs/NF exhibits an exceptionally low cell voltage (1.48V@10mAcm-2) and outstanding durability, surpassing most of the reported Ni-based bifunctional materials. Density functional theory (DFT) further confirms the heterostructure can optimize the Gibbs free energies of H and O-containing intermediates (OH, O, OOH) during HER and OER processes, thereby accelerating the catalytic kinetics of electrochemical water splitting. The findings provide a new design strategy toward low-cost and excellent catalysts for overall water splitting.

Comprehensive Study on the Adsorption and Degradation of Dichlorodiphenyltrichloroethane on Bifunctional Adsorption-Photocatalysis Material TiO2/MCM-41 Using Quantum Chemical Methods.

The adsorption and degradation capacities of dichlorodiphenyltrichloroethane (DDT) on a photocatalyst composed of TiO2 supported on the mesoporous material MCM-41 (TiO2/MCM-41) were investigated using density functional theory and real-time density functional theory methods. The van der Waals interactions within the PBE functional were adjusted by using the Grimme approach. The adsorption of DDT was evaluated through analyses involving adsorption energy, Hirshfeld atomic charges, Wiberg bond orders, molecular electrostatic potential, noncovalent interaction analysis, and bond path analysis. The findings reveal that DDT undergoes physical adsorption on pristine MCM-41 or MCM-41 modified with Al or Fe due to the very small bond order (only about 0.15-0.18) as well as the change in total charge of DDT after adsorption is close to 0. However, it chemically adsorbs onto the TiO2/MCM-41 composite through the formation of Ti···Cl coordination bonds because the maximum bond order is very large, about 1.0 (it can be considered as a single bond). The adsorption process is significantly influenced by van der Waals interactions (accounting for approximately 30-40% of the interaction energy), hydrogen bonding, and halogen bonding. MCM-41 is demonstrated to concurrently function as a support for the TiO2 photocatalyst, creating a synergistic effect that enhances the photocatalytic activity of TiO2. Based on the computational results, a novel photocatalytic mechanism for the degradation of DDT on the TiO2/MCM-41 catalyst system was proposed.

Mn-doped nickel–cobalt sulfides as bifunctional electrodes for high-performance supercapacitors and electrocatalysts for hydrogen evolution reactions

The development of active electrode materials with dual functions of energy storage and electrocatalyst is important for future energy storage and energy conversion devices. In this work, manganese-doped nickel cobalt sulfide (Mn-NCS) mesoporous microspheres were prepared via a simple two-step solvent-thermal method and the effects of different Mn2+ doping levels on the electrochemical properties and hydrogen evolution reactions (HER) of the prepared samples were investigated. As a supercapacitor electrode material, optimized Mn0.5-NCS had a maximum specific capacitance of 1175 C g−1 at a current density of 1 A/g and remained an outstanding capacitance retention rate of 81 % at a current density of 20 A/g. The asymmetric supercapacitor was assembled with the optimal electrode material as the positive electrode and activated carbon as the negative electrode, and a high energy density of 55.4Wh kg−1 was achieved at a power density of 797 W kg−1. The Mn0.5-NCS exhibited the best HER performance in alkaline electrolyte, shown as the lowest overpotential of 95 mV and the smallest Tafel slope of 71 mV dec−1 at a current density of 10 mA cm−2. Experimental tests and density functional theory (DFT) calculations revealed that manganese preferentially occupies nickel sites and acted as an electron donor in the electrochemical process to realize the electron redistribution, increasing electron density and accelerating charge transfer. The results indicated that manganese-doped nickel–cobalt sulfides have great potential as bifunctional electrode materials for high-performance supercapacitors and HER.

Bifunctional hybrid magnetic colloidal clusters for efficient oil sludge recovery

Oil contamination of water bodies due to oil spills, industrial waste discharge, oil leaks, etc. poses a major threat to the quality of groundwater, soil, and living organisms. To combat this issue through effective environmental remediation, efficient and cost-effective materials and innovative strategies are required. Here, we report a novel bifunctional magnetic material for efficient oil sludge removal using superparamagnetic colloidal nanocrystal clusters(BSPM-CNC) of nickel ion doped iron oxide with a shell of nitrogen-activated carboxymethyl cellulose char. The BSPM-CNC is synthesized by using a single-step procedure using water as a solvent. The crystallite and cluster size were tuned by varying Ni2+ ion concentration, carboxymethyl cellulose, and urea ratio. The cluster size was found to increase, when the carboxymethyl cellulose and urea ratio was reduced, due to insufficient stabilization of the capping agent that allowed the formation of secondary structures. X-ray photoelectron spectroscopy results confirmed the presence of nitrogen in the shell because of the condensation of OH and carbonyl groups of CMC with amine groups of urea, sp2-type carbon, C-O/N and O-CO bonding states. Laser Raman spectra of the char showed two major bands G and D bands, originating from the sp2 bonds and sp2 microdomains of the bond angle disorder caused by the sp3 hybridizations, respectively. The BSPM-CNC was found to be very efficient for oil sludge removal, where an oil removal efficiency of ∼ 98% was achieved with a cluster loading of 16 mg/L. The mechanism of sorption of oil are π-π interaction between aromatic hydrocarbons and graphitic domains of BSPM-CNC, Lewis-acid base interaction between nitrogenous char and delocalized electron cloud, and absorption into the pores of clusters. Our new approach provides a new platform to produce magnetic nanoclusters for the efficient removal of oil pollutants.

Isolation of Sensing Units and Adsorption Groups Based on MOF-on-MOF Hierarchical Structure for Both Highly Sensitive Detection and Removal of Hg2.

Bifunctional materials have attracted ongoing interest in the field of detection and removal of contaminants because of their integration of two functions, but they exhibit commonly exceptional performance in only one of these two aspects. The interaction between the two functional units of the bifunctional materials may compromise their sensing and adsorption abilities. Guided by the concept of domain building blocks (DBBs), a hierarchical metal-organic framework (MOF)-on-MOF hybrid was designed by growing gold nanoclusters (AuNCs)-embedded zeolitic imidazolate framework 8 (AuNCs/ZIF-8) on the surface of Zr-MOF (UiO-66-NH2) for the simultaneous detection and removal of Hg2+. In the hybrid, the amino groups (-NH2) and AuNCs─which were the adsorption groups and sensing units, respectively, were isolated from each other. Specifically, the adsorption groups (-NH2) were assembled in the inner UiO-66-NH2 layer, while the sensing units (AuNCs) were confined in the outer ZIF-8 layer. This hierarchical structure not only spatially hindered the electron transfer between these two units but also triggered the aggregation-induced emission of AuNCs because of the confinement of ZIF-8 on the AuNCs, thus changing the fluorescence of AuNCs from quenching to enhancement. The newly prepared UiO-66-NH2@AuNCs/ZIF-8 hybrid, as expected, showed an ultralow detection limit (0.42 ppb) and a high adsorption capacity (129.9 mg·g-1) for Hg2+. Overall, this work provides a feasible approach to improve the integrated performance of MOF-based composites based on DBBs.