Dual Active Sites Research Articles

“Switch to love, switch to kill” - The interaction of Co-doped La(OH)3 and peroxymonosulfate achieved highly efficient As(III) removal in water

Materials combing catalytic and adsorption dual active sites are very important for arsenite (As(III)) due to its high mobility in water. Therefore, in this study, a bifunctional walnut-like Co-doped La(OH)3 composites (Co-La) with independent catalytic sites and post-formed adsorption sites were synthesized via a simple hydrothermal method. Nearly 100% As(III) removal can be achieved in Co-La and peroxymonosulfate interaction systems (Co-La/PMS) within 10 min at the molar ratio of PMS to As(III) of 1.2. The results indicate that the combined Co-La adsorption system demonstrated superior performance compared to the Co-La adsorption alone. Precisely, the maximum removal capacity of the system was measured at 243.90 mg·g−1, and the pseudo-first-order kinetic rate constant (k1) was determined to be 1.0771 min−1. These values were significantly greater than those observed for Co-La adsorption alone. Notably, the kinetic rate constant was 239 times faster, and the removal capacity was 4.6 times higher in the combined system. The fast kinetics of As(III) elimination can be elucidated by the production of reactive oxygen species (ROS) such as SO4·-, •OH, O2·- and1O2, which expedite the conversion of As(III) into arsenate (As(V) in this particular system. Meanwhile, the increase in adsorption capacity is ascribed to the fact that PMS can drive La(OH)3 of Co-La to transform into transition states La2SO4(OH)4, thus generating a new exchangeable adsorption site for As(V). A fixed membrane reactor assembled with Co-La was utilized to achieve a near-complete removal of As(III) within 3 min. The Co-La/PMS systems demonstrate exceptional effectiveness in eliminating arsenic from water across diverse real-water metrics, offering a unique perspective and technological progress in purifying water contaminated with arsenic.

A comparative study of RuO2 and Ru reveals the role of oxygen vacancies in electrocatalytic nitrogen reduction to ammonia under ambient conditions

Nitrogen molecule reduction to ammonia requires adsorption and hydrogenation sites. In this study, the nitrogen reduction reaction (NRR) activity of RuO2 and metallic Ru catalysts was studied to explore the role of oxides and metallic dual active sites. Ruthenium oxide nanoparticles displayed an ammonia production rate of 16.5 µg h−1 cm−2 with a Faradaic efficiency (FE) of 0.26% at − 0.15 V vs. RHE in N2-saturated 0.1 M KOH which is 58% higher compared to Ru black (6.8 µg h−1 cm−2 with 0.19% FE at −0.15 Vvs.RHE). This is attributed to the formation of oxygen vacancies (Vo) on the RuO2 surface during cathodic potential polarization, which provides a facile adsorption site for N2 in addition to the Ru4+ active site while the proton supplied via hydrogen spillover from the metal hydride site to the adsorbed Vo-N2 site. This assumption was validated by detailed XPS, XRD, and N2 TPD analysis.

Coordination Engineering of Dual Co, Ni Active Sites in N-Doped Carbon Fostering Reversible Oxygen Electrocatalysis.

The development of affordable and non-noble-metal-based reversible oxygen electrocatalysts is required for renewable energy conversion and storage systems like metal-air batteries (MABs). However, the nonbifunctionality of most of the catalysts impedes their use in rechargeable MAB applications. Moreover, the loss of active sites also affects the long-term performance of the electrocatalyst toward oxygen electrocatalysis. In this work, we report a simplistic yet controllable chemical approach for the synthesis of dual transitional metals such as cobalt, nickel, and nitrogen-doped carbon (CoNi-NC) as bifunctional electrode materials for rechargeable zinc-air batteries (ZABs). The spatially isolated Ni-N4 and Co-N4 active units were rendered for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively. The individual efficacy of both reversible reactions enables an ΔE value of ∼0.72 V, which outperforms several bifunctional electrocatalysts reported in the literature. The half-wave potential (E1/2) and overpotential were achieved at 0.83 V and 330 mV (vs RHE) for ORR and OER, respectively. The peak power density of ZAB equipped with the CoNi-NC catalyst was calculated to be 194 mW cm-2. The present strategy for the synthesis of bifunctional electrocatalysts with dual active sites offers prospects for developing electrochemical energy storage and conversion systems.

Metal Borides as Excellent Co-Catalysts for Boosted and Long-Lasting Fenton-like Reaction: Dual Co-Catalytic Centers of Metal and Boron.

The continuous electron supply for oxidant decomposition-induced reactive oxygen species (ROS) generation is the main contributor for the long-standing micropollutant oxidation in the iron-based advanced oxidation processes (AOPs). Herein, as a new class of co-catalysts, metal borides with dual active sites and preeminent conductive performance can effectively overcome the inherent drawback of Fenton-like reactions by steadily donating electrons to inactive Fe(III). Among the metal borides, tungsten boride (WB) exhibits a significant co-catalytic performance run ahead of common heterogeneous co-catalysts and exceptionally high stability. Based on qualitative and semi-quantitative tests, the hydroxyl radical, sulfate radical, and iron(IV)-oxo complex are all produced in the WB/Fe(III)/PDS system and Fe(IV)-induced methyl phenyl sulfoxide decomposition is up to 72%. Moreover, the production efficiency of ROS and relative proportions of radical and nonradical pathways change with various experimental conditions (dosages of PDS, WB, and solution pH) and water matrices. The rate-determining step of Fe(II) regeneration is greatly accelerated resulting from the synergetic effect between exposed metallic reactive sites and nonmetallic boron with reductive properties of WB. In addition, the self-dissolution of surface tungsten oxide and boron oxide leads to a renovated surface for sustainable Fe(III) reduction in long-term operations. Our discovery provides an efficient and sustainable strategy in the field of enhanced AOPs for water remediation.

Co-Fe3C pair sites catalyst with heterometallic dual active sites for efficient oxygen reduction reaction

Newly emerging metal-based pair sites catalysts show great potential because they can provide more metal active centers with synergistic effect for green catalysis, compared with single site catalysts. However, both the synthesis and catalytic mechanisms of the pair sites catalyst with new structural features need to be developed vigorously to promote the desired chemical reactions, especially carbon-based metal catalysts for green energy storage and conversion devices. Herein, we constructed highly active Co-Fe3C pair sites on N-doped graphite catalyst (CNCo-Fe3C) by a two-step strategy, which have electron interactions of heterometallic atoms and can play better synergistic effect. X-ray absorption spectra and density functional theory (DFT) calculation further identify the presence of heterometallic active sites in the pair sites catalyst, resulting in electron redistribution and positive d-band center due to the electron interactions. The more positive d-band center model predicts the optimization of the adsorption energy of oxygen-containing intermediates, and reduces the energy barrier of the determining step. This further results in superior oxygen reduction reaction (ORR) performance with a half-wave potential of 0.90 V versus reversible hydrogen electrode (vs.RHE) and superior long-term stability for about 20 h with only 2.3 % decrease at 0.75 V vs.RHE in 0.1 M KOH solution. Additionally, it also shows significant peak power density of 124 mW cm−2 and prominent cycling stability performance exceeding 400 h at 5 mA cm−2 in the Zn-air battery (ZAB) test, which is higher than that of Pt/C catalyst. This work provides a new idea for the regulation of intrinsic activity of non-noble metal ORR catalysts through the synergistic effect of the pair sites.

Platinum and Frustrated Lewis Pairs on Ceria as Dual-Active Sites for Efficient Reverse Water-Gas Shift Reaction at Low Temperatures.

The low-temperature reverse water-gas shift (RWGS) reaction faces the following obstacles: low activity and unsatisfactory selectivity. Herein, the dual-active sites of platinum (Pt) clusters and frustrated Lewis pair (FLP) on porous CeO2 nanorods (Ptcluster /PN-CeO2 ) provide an interface-independent pathway to boost high performance RWGS reaction at low temperatures. Mechanistic investigations illustrate that Pt clusters can effectively activate and dissociate H2 . The FLP sites, instead of the metal and support interfaces, not only enhance the strong adsorption and activation of CO2 , but also significantly weaken CO adsorption on FLP to facilitate CO release and suppress the CH4 formation. With the help of hydrogen spillover from Pt to PN-CeO2 , the Ptcluster /PN-CeO2 catalysts achieved a CO yield of 29.6 %, which is very close to the thermodynamic equilibrium yield of CO (29.8 %) at 350 °C. Meanwhile, the Ptcluster /PN-CeO2 catalysts delivered a large turnover frequency of 8720 h-1 . Moreover, Ptcluster /PN-CeO2 operated stably and continuously for at least 840 h. This finding provides a promising path toward optimizing the RWGS reaction.

Modulating adsorbed hydrogen drives electrochemical CO2-to-C2 products

Electrocatalytic CO2 reduction is a typical reaction involving two reactants (CO2 and H2O). However, the role of H2O dissociation, which provides active *H species to multiple protonation steps, is usually overlooked. Herein, we construct a dual-active sites catalyst comprising atomic Cu sites and Cu nanoparticles supported on N-doped carbon matrix. Efficient electrosynthesis of multi-carbon products is achieved with Faradaic efficiency approaching 75.4% with a partial current density of 289.2 mA cm−2 at −0.6 V. Experimental and theoretical studies reveal that Cu nanoparticles facilitate the C-C coupling step through *CHO dimerization, while the atomic Cu sites boost H2O dissociation to form *H. The generated *H migrate to Cu nanoparticles and modulate the *H coverage on Cu NPs, and thus promote *CO-to-*CHO. The dual-active sites effect of Cu single-sites and Cu nanoparticles gives rise to the catalytic performance.

S-scheme P-doped g-C3N4/BiOBr heterojunction with oxygen vacancy for efficient photocatalytic degradation of phenanthrene: Enhance molecular oxygen activation and mechanism insights

S-scheme heterojunction photocatalysts, renowned for their efficient charge separation and strong redox properties, have gained considerable attention in pollutant remediation. Hence, a dual-active site S-scheme P-doped g-C3N4/BiOBr with oxygen vacancy (PCN/BiOBr-OV) was synthesized. The optimized PCN/BiOBr-OV(2:1) exhibited an impressive degradation rate of 99.2% (kobs = 0.04048 min−1) and superior efficiency for various water conditions. Synergistic effects resulting from P-doping and oxygen vacancy (OV) enhanced charge transfer and promoted S-scheme heterojunction generation. The S-scheme charge transfer pathway in PCN/BiOBr-OV was validated using in-situ irradiation X-ray photoelectron spectroscopy (in-situ irradiation XPS). Experimental results and density functional theory (DFT) calculations provided direct evidence supporting the role of P-doping and OV in facilitating water and oxygen adsorption and activation at dual-active sites, leading to the generation of active species (h+, OH, and O2▪−). Quantum mechanical theory and intermediate product analysis effectively elucidated the ring-opening process of PHE. The highly efficient PCN/BiOBr-OV photocatalyst represents a promising strategy for the environmental remediation of PHE.

L-phenylalanine-assisted construction of hierarchically structured Fe(OH)3@Co2(OH)2CO3 with enhanced catalytic activities for the degradation of persistent organic pollutants

In this work, a flower-like Fe(OH)3@Co2(OH)2CO3 catalyst was prepared via the confinement effects provided by L-phenylalanine, which favored the heterostructure construction of active iron centers (Fe(OH)3) anchored on the Co2(OH)2CO3 nanosheet supports. Benefiting from the created electron-transfer interface and dual metal active sites, the limitation of redox cycling was broken and exhibited highly efficient catalytic activities, the optimal Fe(OH)3@Co2(OH)2CO3 catalyst showed comparable catalytic performance for the degradation of dye (degradation degree of 99% methylene blue and orange II within 18 min). In addition, the prepared catalysts were employed for the efficient removal of antibiotics (tetracycline (98.9%), norfloxacin (92.5%) and doxycycline hyclate (90.2%). Besides, the preferred nanofibrous composite membranes prepared by combination of nanofibrous membranes (NFMs) with Fe(OH)3@Co2(OH)2CO3 catalysts possessed considerable potential for large-scale MB removal (treatment capacity of 238.5 L m−2 and permeability of 191.8 L m−2 h−1 driven by gravity) and stability (182.7 L m−2 of treatment capacity was achieved in the third run). The strategy of construction of rapid interface-redox on the heterogenous catalysts was designed to enhance catalytic performance, which provided a promising chance for the efficiently large-scale removal of dyes and antibiotics.

Visible light-assisted hydrogen generation from ammonia borane over Z-Scheme NiO-CuO heterostructures

The design and fabrication of cheap and high-efficiency catalysts for ammonia borane (AB) hydrolysis for hydrogen production is crucial for its commercial applications. Improvement of the catalytic performance of the catalysts with the assistance of sunlight, a costless resource, is extremely attractive. Herein, we have constructed Z-scheme heterostructured VO-NiO-CuO catalysts with strong interfacial electronic interactions and abundant oxygen vacancies to enhance hydrogen production from NH3BH3 solution under visible light illumination. The as-prepared VO-NiO-CuO catalysts exhibit excellent catalytic activity with a high turnover frequency (TOF) of 35.3 molH2 molcat.-1 min−1 toward AB hydrolysis under visible light. It is demonstrated that excellent catalytic performance is highly related to the effective separation and migration of charge on the catalyst surface. As a result, dual active sites were created, making it easier for various reactants to be adsorbed and activated on the catalyst surface. Furthermore, the density functional theory (DFT) calculations indicate that the adsorption and activation of H2O occurred mainly at the Ni site of VO-NiO-CuO. When the VO-NiO-CuO is irradiated with visible light, the photogenerated electrons assembled on the conduction band were transferred to the O atom through the Ni-O bond, which made the bond length of H2O molecules longer and OH bonds more prone to breaking, thus facilitating AB hydrolysis under illumination. The findings in this work pave the way to design novel and efficient heterostructured catalysts for fast hydrogen release from NH3BH3 under visible light irradiation.

Dual‐Site Activation Coupling with a Schottky Junction Boosts the Electrochemiluminescence of Carbon Nitride

AbstractRobust electrochemiluminescence (ECL) of carbon nitride (CN) requires efficient electron‐hole recombination and the suppression of electrode passivation. In this work, Au nanoparticles and single atoms (AuSA+NP) loaded on CN serve as dual active sites that significantly accelerate charge transfer and activate peroxydisulfate. Meanwhile, the well‐established Schottky junctions between Au NPs and CN act as electron sinks, effectively trapping over‐injected electrons to prevent electrode passivation. As a result, the porous CN modified with AuSA+NP exhibits an enhanced and stable ECL emission, with a minimal relative standard deviation of 0.24 %. Furthermore, the designed ECL biosensor based on AuSA+NP‐CN shows a remarkable performance in detecting organophosphorus pesticides. This innovative strategy has the potential to offer new insights into strong and stable ECL emission for practical applications.

Dual-Site Activation Coupling with a Schottky Junction Boosts the Electrochemiluminescence of Carbon Nitride.

Robust electrochemiluminescence (ECL) of carbon nitride (CN) requires efficient electron-hole recombination and the suppression of electrode passivation. In this work, Au nanoparticles and single atoms (AuSA+NP ) loaded on CN serve as dual active sites that significantly accelerate charge transfer and activate peroxydisulfate. Meanwhile, the well-established Schottky junctions between Au NPs and CN act as electron sinks, effectively trapping over-injected electrons to prevent electrode passivation. As a result, the porous CN modified with AuSA+NP exhibits an enhanced and stable ECL emission, with a minimal relative standard deviation of 0.24 %. Furthermore, the designed ECL biosensor based on AuSA+NP -CN shows a remarkable performance in detecting organophosphorus pesticides. This innovative strategy has the potential to offer new insights into strong and stable ECL emission for practical applications.

Fe-Co/Fe3C dual active sites catalysts supported on nitrogen-doped graphitic carbon for ultrafast degradation of high concentration Rhodamine B

Iron-based catalysts have garnered great attention as alternatives for Fenton-like catalysts in the degradation of organic compounds. However, there is a demand for the synthesis of highly efficient iron-based catalysts that can solve the problems of iron dissolution and poor stability. Herein, nitrogen-doped graphitic carbon-supported Fe-Co/Fe3C dual active sites catalyst (Fe-Co/Fe3C-NC) is successfully prepared by ball milling method combined with subsequent high-temperature self-reduction. 0.5 wt%-Fe-Co/Fe3C-NC shows high efficiency in the activation of peroxymonosulfate (PMS) for the ultrafast degradation of high concentration Rhodamine B (200 mg/L of RhB is completely degraded within 8 min and the degradation rate constant is as high as 0.5066 min−1), as well as high stability and good reproducibility, attributing to the synergistic mechanism between the dual active sites (Fe-Co and Fe3C) and the adsorption sites (Fe3C and pyrrolic-N). Chemical quenching experiments and electron paramagnetic resonance indicate that the prepared 0.5 wt%-Fe-Co/Fe3C-NC exhibits outstanding activation for PMS by generating reactive oxygen species (SO4•−, •OH, 1O2) and high-valent FeCo=O species. This work shows useful insights into the synthesis of iron-based dual active sites catalysts, providing exciting chances for the highly efficient degradation of high concentration organic wastewater.

Revealing promotion of interfacial Pt–O–Fe oxygen bridge structure in PtFe/graphene synthesized by a four-electrode electrochemical system on water splitting

To promote kinetic rate of half reactions in water splitting, we synthesized a bifunctional PtFe/graphene with dual active sites by a facile self-designed four-electrode electrochemical method. Characterization data indicate interfacial oxygen bridge structure of Pt–O–Fe is expectedly formed and electrons transfer from Fe to Pt via this bridge structure. This unique interfacial structure not only regulates electronic structure of Pt and Fe, but also offers interfacial electron-transfer channel to improve overall conductivity, which essentially enhances intrinsic activity towards acidic HER and alkaline OER. For HER, the best Pt–Fe/G shows the mass activity of 4239.3 mA mg−1 at −0.063 V, 3.79 times higher than that of Pt/G (1118.5 mA mg−1) and 5.02 times higher than that of commercial Pt/C (843.1 mA mg−1) catalyst, respectively. Introduction of Fe to Pt decreases the energy barrier of HER process (ΔG∗), and results in conversion of rate-limiting step from H+ adsorption (Volmer step) to H∗ desorption (Tafel step). For OER, the greatest PtFe/G exhibits an overpotential of lower 26 mV (10 mA cm-2) than commercial RuO2 and its mass activity is 16.7 times higher than Fe/G. The formed Pt–O–Fe bond effectively elevates the electrophilic properties and facilitates adsorption of OH−, contributing to the change of rate-limiting step and enormous decrease of reaction activation energy (Ea). This work inspires researchers to construct efficient interfacial oxygen bridge structure to enhance electrocatalytic performance for water splitting and design novel electrochemical method for synthesis of graphene-based composites.

Dual active sites over TiO2 homojunction through tungsten doping and oxygen vacancies for enhanced photoelectrochemical properties

The introduction of dual active sites is a feasible strategy to enhance the photoelectrochemical (PEC) water splitting, but rational design based on structural construction and chemical composition is still a challenge. Herein, a homojunction composed of tungsten (W) doped titanium dioxide (TiO2) nanorods and oxygen vacancies modified TiO2 nanosheets is prepared via solid-state diffusion-hydrothermal method to improve the PEC activities. The TiO2 homojunction with dual active sites shows a 136 times enhancement in photocurrent density over the pristine TiO2 nanorods. PEC investigation reveals that the element W doped into the lattice of TiO2 causes the downshift of conduction band, and the formed defects state acting as the trapping sites could reduce photoinduced electron-hole pairs recombination rates. Moreover, the addition of polyvinylpyrrolidone leads to the generation of oxygen vacancies within TiO2 nanosheets, which facilitates the carrier transfer, and meanwhile suppresses the charge recombination. In addition, the type-II homojunction within the hierarchical nanostructure could not only advance the separation of photogenerated electron-hole pairs, but also provide more exposed active sites due to the enhanced specific surface area. The synergistic effect of doping, oxygen vacancies and homojunctions endows the considerably improved PEC performance.

Integrating dual active sites on heterogeneous bimetallic selenide to facilitate hydrogen evolution and ethanol oxidation

The combination of the dual sites of hydrogen evolution reaction (HER) and ethanol oxidation reaction (EOR) into a single electrocatalyst is indispensable for energy-saving hydrogen generation. However, such combination is hindered for practical applications due to the challenges regarding fewer active sites on electrocatalysts. Herein, we prepared a heterogeneous nanostructure comprising of ZnSe and MnSe embedded in nitrogen-doped carbon (namely ZnSe-MnSe), where the Mn elements can be controllably introduced into ZnSe to modulate the electronic states and thus boost the charge transfer from MnSe to ZnSe. The interfacial electronic regulation stimulates the formation of well-defined HER and EOR active centers, which could optimize hydrogen adsorption energy and ethanol adsorption property, thus fulfilling superior HER and EOR performances. Specifically, due to the more propitious thermodynamics and kinetics of EOR triggered by ZnSe-MnSe electrocatalyst than those of OER, the demanded cell potential of ethanol-assisted water electrolysis is markedly lower than water electrolysis. Besides, the oxidation product ethyl acetate in this case is more valuable than oxygen from water electrolysis. This work presents a promising tactic in designing future energy-saving hydrogen generation applications and related high-performance electrocatalysts.

Co doping regulating electronic structure of Bi2MoO6 to construct dual active sites for photocatalytic nitrogen fixation

Although photocatalytic nitrogen reduction reaction (PNRR) is a green ammonia synthesis technology, it still encounters low adsorption/activation efficiency of N2 and lack of reaction active sites. Element doping is an efficient strategy to regulate electronic structure of catalyst. Nevertheless, the mechanism of the effect of doping elements on the N2 adsorption/activation, reaction active site and energy barriers is not well unraveled. Taking Co doped Bi2MoO6 (Co-Bi2MoO6) as a model photocatalyst, density functional theory (DFT) and experiment study were used to investigate the mechanism of Co doping on the PNRR performance over Bi2MoO6. DFT results reveal that Co doping regulates the electronic structure, activates Bi sites of Co-Bi2MoO6 and provides new Co active sites, thus constructing dual active sites for PNRR. Benefited from dual active sites for effectively adsorption/activation N2, the as-fabricated 3% Co-Bi2MoO6 exhibit the maximum NH3 generation rate of 95.5 μmol·g−1·h−1 without sacrificial agents, which is 7.2 times that of Bi2MoO6. Furthermore, the detail mechanism of NN bond adsorption/activation and hydrogenation reaction on Co-Bi2MoO6 was also proposed according to in-situ FTIR and DFT results. This study provides a promising strategy to design catalysts with dual active sites for PNRR, which is of great significance to the popularization of other material systems.

Construction of FeIn2S4/Palygorskite nanocomposite for photocatalytic nitrogen fixation coupled with biomass conversion

Photocatalytic N2 fixation coupled with biomass conversion into value-added chemicals is an attractive strategy for achieving sustainable and ecological development. Herein, the octahedral cation sites of acid-activated palygorskite (Pal) were substituted by Fe ions using microwave hydrothermal method to achieve lattice reconstruction. Then FeIn2S4/Fe-Pal (FIS/Fe-Pal) composites were synthesized by loading indium iron sulfide on the surface of Fe-Pal, which were employed for photocatalytic nitrogen fixation coupling with cellulose biomass conversion. When the mass ratio of Fe-Pal to FeIn2S4 was 0.4:1, the photocatalyst showed the highest NH4+ production of 583 μmol/g and formate production of 265 μmol/g after 6 h illumination. The sulfur vacancies together with Fe ions in FIS/Fe-Pal formed dual active sites favoring the adsorption and activation of N2 in glucose solution. In addition, the introduction of FeIn2S4 expanded the light absorption range improving the light utilization. This work opens up a new window for the coupling of nitrogen fixation and biomass conversion by taking advantage of natural clay and solar energy.

Acceleration of Fe3+/Fe2+ cycle in garland-like MIL-101(Fe)/MoS2 nanosheets to promote peroxymonosulfate activation for sulfamethoxazole degradation

Iron-based molybdenum disulfide (Fe-MoS2) has emerged as a Fenton-like catalyst for the highly efficient degradation of antibiotics, but the structure–activity relationship remains elusive. Herein, garland-like MIL-101(Fe)/MoS2 nanosheets (MMS) with dual metal active sites (Fe and Mo) and rich sulfur vacancies were fabricated to directly activate peroxymonosulfate (PMS) for fast degradation of different organic pollutants (phenols, dyes and drugs), even in real water bodies. The MMS exhibited extremely fast catalytic rate constant of 0.289 min−1 in the degradation of sulfamethoxazole (SMX), which was about 36 and 29 times that of single MoS2 (0.008 min−1) and MIL-101(Fe) (0.01 min−1). Moreover, MMS with good stability and reusability could reach 92% degradation of SMX after 5 cycles. Quenching experiments and electron spin resonance (ESR) tests revealed that hydroxyl radicals (.OH) and singlet oxygen (1O2) were the dominant reactive oxygen species (ROS) for SMX degradation. The integration of experimental works, characterization techniques and density functional theory (DFT) calculations unraveled that the formation of sulfur vacancies in MMS catalyst could expose more Mo sites, improve the charge density and boost the electron transfer, which was conducive to accelerating the Fe3+/Fe2+ cycle for enhancing the activation of PMS. Finally, the C-N, N-O, S-N, C-O and C-S bonds of SMX were easily attacked by ROS to generate the nontoxic intermediates in the MMS/PMS/SMX system. This study offers a new approach to designing high-performance Fe-MoS2 catalysts for the removal of organic pollutants.

Synergism of NiFe layered double hydroxides/phosphides and Co-NC nanorods array for efficient electrocatalytic water splitting

The green hydrogen route provides a reliable way to reduce dependence on fossil fuels. Hydrogen production by water electrolysis is an efficient way to convert unstable renewable energy sources into hydrogen energy. Herein, a rod-like N-doped carbon nanorods array cooperated with layered double hydroxide (Ni2Fe@Co-NC/CC) and a tri-metal phosphides composite (P-Ni2Fe@Co-NC/CC) is fabricated, which is believed can facilitate the electron and mass transfer efficiency. The Co element in Ni2Fe@Co-NC/CC can promote the formation of high-valence Ni and activate lattice oxygen to form abundant dual OER active sites. While the P-Ni2Fe@Co-NC/CC can obtain optimized hydrogen adsorption free energy due to synergistic effect of trimetallic phosphides and nitrogen-doped carbon structure to promotes the HER progress. Therefore, due to the synergistic effect between metal hydroxide/phosphide and Co-decorated NC nanorods array, low overpotentials of 240 and 137 mV at 100 mA cm−2 can be achieved for OER and HER with excellent electrocatalytic stability. Besides, the Ni2Fe@Co-NC/CC//P-Ni2Fe@Co-NC/CC device can afford cell voltage of 1.579 V at 50 mA cm−2 in water splitting, which demonstrate a new idea for rational designed electrocatalytic water splitting composites towards high activity and stability.