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The synthesis and characterization of a Co/Fe mixed‐metal banana‐shaped polyoxometalate with the formula [(Co2.5Fe0.5(H2O)PW9O34)2(PW6O26)]16− (Co5Fe) is reported. This transition‐metal‐substituted polyoxometalate readily assembles from its components in a one‐pot reaction and crystallizes in the monoclinic space group P21/c. The structure of Co5Fe can be considered a double sandwich composed by two B‐α‐{Co2.5Fe0.5PW9O40} Keggin units, in which one coordinatively saturated octahedral metal position is equally occupied by Co(II) and Fe(III) ions with a 50 % of site occupancy. These Keggin units are linked via a hexalacunary Keggin unit {PW6O26}. Single crystal X‐ray diffraction and magnetic measurements support the proposed atom arrangement within the crystal structure. Magnetic measurements of these double trimeric unit {Co2.5Fe0.5O13}2 show a combination of antiferromagnetic interactions, the presence of spin frustration, and the first‐order spin‐orbit coupling of Co(II) ions. Electrocatalytic water oxidation measurements show that Co5Fe displays low stability in both homogeneous and heterogeneous conditions. This is evidenced by the constant increase on the catalytic currents over time together with the appearance of polyoxometalate‐derived electrode‐bound species that can be responsible for the observed catalytic activity. [ABSTRACT FROM AUTHOR]

To address the ever‐increasing societal demand for clean energy, electrocatalytic water splitting has attracted considerable interest for the efficient production of H2 and O2. However, the oxygen evolution reaction (OER) is inherently sluggish and poses a significant challenge to the overall water splitting process. As a result, extensive research efforts have been dedicated to pursuing various approaches in developing efficient electrocatalysts for water oxidation. The oxygen‐evolving center (OEC) of Photosystem II (PS II) is a natural model giving the prominent reference. Hence, this review discusses recent advances in the design of artificial electrocatalyst inspired by PS II. The discussion begins with a brief introduction to the fundamentals of electrocatalytic water oxidation and PS II. Subsequently, the progress of the novel electrocatalysts inspired by PS II is presented in the following two aspects: engineering various transition metal clusters to mimic the inorganic metal cluster of OEC (Mn4O5Ca), and utilizing different ligands to simulate the protein and amino acid environment around [Mn4O5Ca]. In addition to outlying the structures, catalytic activities, and corresponding mechanisms of these prepared catalysts, this present review concludes by proposing several effective development perspectives to this emerging field that warrant further investigation. [ABSTRACT FROM AUTHOR]

The development of efficient and economical electrocatalysts for oxygen evolution reaction (OER) is of paramount importance for the sustainable production of renewable fuels and energy storage systems; however, the sluggish OER kinetics involving multistep four proton-coupled electron transfer hampers progress in these systems. Fortunately, surface reconstruction offers promising potential to improve OER catalyst design. Anion modulation plays a crucial role in controlling the extent of surface reconstruction and positively persuading the reconstructed species' performances. This review starts by providing a general explanation of how various types of anions can trigger dynamic surface reconstruction and create different combinations with pre-catalysts. Next, the influences of anion modulation on manipulating the surface dynamic reconstruction process are discussed based on the in situ advanced characterization techniques. Furthermore, various effects of survived anionic groups in reconstructed species on water oxidation activity are further discussed. Finally, the challenges and prospects for the future development directions of anion modulation for redirecting dynamic surface reconstruction to construct highly efficient and practical catalysts for water oxidation are proposed. [ABSTRACT FROM AUTHOR]

Electrochemical oxygen evolution reaction (OER) is hampering the development of hydrogen production on a large scale, accompanied with difficulties in achieving high current density (>1 A cm-2) and poor stability for current catalysts. Herein, the FeCoW hydroxides supported on Ni foam (FeCoW/NF) are synthesized via a simple and controllable electrodeposition method, which deliver the high current density of 1.28 A cm-2 at the 770-mV overpotential vs reversible hydrogen electrode (RHE), together with steady operation at 100 mA cm-2 for 100 h in 1 M KOH. Moreover, the as-prepared FeCoW/NF electrocatalyst possesses an ultralow overpotential of 360 mV vs RHE to drive oxygen evolution reaction for the current density of 100 mA cm-2, outperforming most current transition metal-based catalysts. This work enables opportunities in exploring promising paths to achieve non-noble electrocatalysts for scale-up water spitting at industrial current. [Display omitted] • Synthesize FeCoW hydroxides via facile one-step electrodeposition. • Exhibit overpotential of 300 mV to reach 10 mA cm−2 for OER. • Achieve high current activity of 1 A cm−2 at ultralow overpotential of 650 mV. • Operate 100 h at 100 mA cm−2 with negligible attenuation. [ABSTRACT FROM AUTHOR]

The scaled-up synthesis of organic-free monolayer nanomaterials is highly desirable, especially in obtaining green energy by electrocatalysis. In this study, a method for the scaled-up synthesis of the series of monolayer layered double hydroxides (LDHs) without the addition of organic solvents is reported via the separate nucleation and aging steps process. The resulting monolayer LDHs with the thicknesses of less than 1 nm showed a narrow thickness distribution. X-ray absorption fine-structure revealed that monolayer NiFe-LDH nanosheets have a number of oxygen and metal vacancies defects. As a practical application, monolayer NiFe-LDH nanosheets containing defects showed an enhanced electrocatalytic water oxidation activity compared with that of bulk NiFe-LDH. Density functional theory calculations uncovered that excellent catalytic activity is attributed to vacancies defects. The proposed method is an economical and universally applicable strategy for the scaled-up production of monolayer LDHs.

Catalyst development for water splitting to afford hydrogen as a green source of energy is one of the major areas of research in the pursuit of sustainable energy technology solution. Herein, the electrocatalytic water oxidation behaviour of two different Co‐pdc (H2pdc=pyridine‐2,5‐dicarboxylic acid) based metal‐organic frameworks (MOFs) of different dimensionalities (2D and 1D) is reported. 2D‐MOF {[Co(pdc)(H2O)2] ⋅ H2O}n acts as the mother which transforms into daughter 1D‐MOF {[Co(pdc)(H2O)2] ⋅ 7H2O}n via consecutive dehydration and rehydration. Within 2D‐MOF, the Co2+ shows six coordinated octahedral geometry with two coordinated water molecules and for the 1D‐MOF, Co2+ shows five coordinated square pyramidal geometry having two coordinated water molecules and one open metal site. Both the MOFs show excellent stability over a pH range of 3 to 11 even after 24 hours and show OER activity from neutral to alkaline medium. The MOFs retain their crystalline structure even after OER at neutral pH but eventually gets decomposed; but they are converted into their (oxy)hydroxides at pH 14. Interestingly, 1D MOF shows superior activity in both neutral and alkaline medium over the 2D framework for OER due to presence of open metal sites, better electrical conductivity and larger electrochemically active surface area. [ABSTRACT FROM AUTHOR]

Electrochemical water oxidation over high-efficiency (Ca, Mg, or Y) doped lithium metal (Ni) phosphate electrocatalysts

The oxygen evolution reaction (OER) activity of single‐atom catalysts (SACs) is closely related to the coordination environment of the active site. Oxygen‐coordinated atomic metal species bring about unique features beyond nitrogen‐coordinated atomic metal species due to the fact that the M–O bond is weaker than the M–N bond. Herein, a series of metal–oxygen–carbon structured low‐nucleus clusters (LNCs) are successfully anchored on the surface of multiwalled carbon nanotubes (M‐MWCNTs, M = Ni, Co, or Fe) through a foolproof low‐temperature gas transfer (300°C) method without any further treatment. The morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive characterizations. The synthetic Ni‐MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions, transcending the performances of Co‐MWCNTs, Fe‐MWCNTs and RuO2. Density functional theory calculations reveal that the moderate oxidation of low‐nucleus Ni clusters changes the unoccupied orbital of Ni atoms, thereby lowering the energy barrier of the OER rate‐limiting step and making the OER process more energy‐efficient. This study demonstrates a novel versatile platform for large‐scale manufacturing of oxygen‐coordinated LNC catalysts. [ABSTRACT FROM AUTHOR]

Abstract The oxygen evolution reaction (OER) activity of single‐atom catalysts (SACs) is closely related to the coordination environment of the active site. Oxygen‐coordinated atomic metal species bring about unique features beyond nitrogen‐coordinated atomic metal species due to the fact that the M–O bond is weaker than the M–N bond. Herein, a series of metal–oxygen–carbon structured low‐nucleus clusters (LNCs) are successfully anchored on the surface of multiwalled carbon nanotubes (M‐MWCNTs, M = Ni, Co, or Fe) through a foolproof low‐temperature gas transfer (300°C) method without any further treatment. The morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive characterizations. The synthetic Ni‐MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions, transcending the performances of Co‐MWCNTs, Fe‐MWCNTs and RuO2. Density functional theory calculations reveal that the moderate oxidation of low‐nucleus Ni clusters changes the unoccupied orbital of Ni atoms, thereby lowering the energy barrier of the OER rate‐limiting step and making the OER process more energy‐efficient. This study demonstrates a novel versatile platform for large‐scale manufacturing of oxygen‐coordinated LNC catalysts.

As the lightest metal, the reversible insertion/extraction properties of lithium have been key findings in lithium metal oxide chemistry. Lithium has been widely used in the oxygen evolution reaction (OER), and the reaction mechanism of lithium‐mediated metal oxides has both similarities and uniqueness compared to typical dual metal oxides. Notably, the insertion/extraction of lithium during the OER is also crucial for the construction of novel surface reconstruction models. This review aims to provide the concepts of general OER pathways and key features of dual metal oxides for the OER. As a comparison then the development of lithium metal oxides for the OER is introduced and the chemistry underlying lithium metal oxide catalysts is unveiled. This review also examines the challenges remaining for the relevant catalysts, with prospects for further improving their OER activities. [ABSTRACT FROM AUTHOR]

Based on the low‐cost and relatively high catalytic activity, considerable efforts have been devoted towards developing redox‐active transition metal (TM)‐oxygen electrocatalysts for the alkaline oxygen evolution reaction (OER) while the role of redox‐inactive alkaline earth metals has often been neglected in OER. Herein, for the first time, we developed a novel ternary intermetallic CaFe6Ge6 precatalyst, whose surface rapidly transforms into a porous ultrathin Ca−Fe−O heteroshell structure during alkaline OER through the oxidative leaching of surficial Ge. Benefiting from synergistic effects, this highly efficient OER‐active material with distinct Ca−Fe−O layers has a large electrochemical surface area and more exposed active Fe sites than a Ca‐free FeOx phase. Also, the presence of Ca in Ca−Fe−O is responsible for the enhanced transport and activation of hydroxyls and related OER reaction intermediate as unequivocally illustrated by a combination of quasi in‐situ Raman spectroscopy and various ex‐situ methods. [ABSTRACT FROM AUTHOR]

We report amorphous iridium oxide (IrO2) and tantalum oxide (Ta2O5) electrocatalysts supported on titanium fiber felt as effective anodes for oxygen evolution reaction (OER). The IrO2-Ta2O5 electrode, prepared by thermal decomposition of the precursor added with polyethylene glycol (PEG), achieved a current density of 10 mA cm−2 at a low overpotential of 0.24 V in a sulfuric acidic solution. The high OER activity is because PEG generated mesopores in the amorphous IrO2-Ta2O5 layer after heating at 350 °C. The increase in the double-layer capacitance, proportional to the electrochemically active surface area (ECSA), was responsible for the high current density at low overpotentials. Furthermore, the addition of the polymer to the precursor suppressed the dissolution of Ir from the anode during the OER stability test and improved the durability of the IrO2-Ta2O5 electrocatalyst coated on the Ti felt.

Abstract Efficient electrocatalysts for the oxygen evolution reaction (OER) are highly desirable because of the intrinsically sluggish kinetics of OER. Herein, core–shell structured nanospheres of NiFexSn@NiFe (oxy)hydroxide (denoted as NiFexSn‐A) are prepared as active OER catalysts by a facile electrochemical strategy, which includes electrodeposition of NiFexSn alloy nanospheres on carbon cloth (CC) and following anodization. The alloy core of NiFexSn could promote charge transfer, and the amorphous shell of NiFe (oxy)hydroxide is defect‐rich and nanoporous due to the selective electrochemical etching of Sn in alkaline medium. The optimized catalyst of NiFe0.5Sn‐A displays a remarkable OER performance with a low overpotential of 260 mV to reach the current density of 10 mA cm−2, a small Tafel slope of 50 mV dec−1, a high turnover frequency of 0.194 s−1 at an overpotential of 300 mV, and a robust durability. Further characterizations indicate that the superior OER performance of the core–shell structured NiFe0.5Sn‐A nanospheres might originate from abundant active sites and small charge transfer resistance. This work brings a new perspective to the design and synthesis of core–shell structured nanospheres for electrocatalysis through a facile electrochemical strategy.

Two new open Wells-Dawson-type polyoxometalates (POMs), K7H2[K(Co(H2O)4)2Co(H2O)2(Si2W18O66)]·22H2O and K7H2[{C(NH2)3} (Co(H2O)4)2Co(H2O)2(Si2W18O66)]·20H2O (abbreviated as K-Co3Si2W18 and C(NH2)3-Co3Si2W18), were synthesized by conventional synthesis and characterized by X-ray single crystal and powder diffraction (XRSCD and XRPD), IR and UV-vis absorption spectra. XRSCD analysis reveals that two tungstosilicates have similar anionic structures with an open Wells-Dawson anion [Si2W18O66]16− and three Co2+ ions. The electrocatalytic activities of both compounds toward the reduction of H2O2 and NaNO2 were studied. Also their electrocatalytic water oxidation performance was evaluated at neutral pH. [ABSTRACT FROM AUTHOR]

Efficient electrocatalysts for the oxygen evolution reaction (OER) are highly desirable because of the intrinsically sluggish kinetics of OER. Herein, core–shell structured nanospheres of NiFexSn@NiFe (oxy)hydroxide (denoted as NiFexSn‐A) are prepared as active OER catalysts by a facile electrochemical strategy, which includes electrodeposition of NiFexSn alloy nanospheres on carbon cloth (CC) and following anodization. The alloy core of NiFexSn could promote charge transfer, and the amorphous shell of NiFe (oxy)hydroxide is defect‐rich and nanoporous due to the selective electrochemical etching of Sn in alkaline medium. The optimized catalyst of NiFe0.5Sn‐A displays a remarkable OER performance with a low overpotential of 260 mV to reach the current density of 10 mA cm−2, a small Tafel slope of 50 mV dec−1, a high turnover frequency of 0.194 s−1 at an overpotential of 300 mV, and a robust durability. Further characterizations indicate that the superior OER performance of the core–shell structured NiFe0.5Sn‐A nanospheres might originate from abundant active sites and small charge transfer resistance. This work brings a new perspective to the design and synthesis of core–shell structured nanospheres for electrocatalysis through a facile electrochemical strategy. [ABSTRACT FROM AUTHOR]

Significant progress has been made in designing single-site molecular Ru(II)-polypyridyl-aqua catalysts for homogenous catalytic water oxidation. Surface binding and transfer of the catalytic reactivity onto conductive substrates provides a basis for heterogeneous applications in electrolytic cells and dye-sensitized photoelectrosynthesis cells (DSPECs). Earlier efforts have focused on phosphonic acid (-PO3H2) or carboxylic acid (-CO2H) bindings on oxide surfaces. However, issues remain with limited surface stabilities, especially in aqueous solutions at higher pH under conditions that favor water oxidation by reducing the thermodynamic barrier and accelerating the catalytic rate using atom-proton transfer (APT) pathways. Here, we address the problem by combining silane surface functionalization and surface reductive electropolymerization on mesoporous, nanofilms of indium tin oxide (ITO) on fluorinedoped tin oxide (FTO) substrates (FTO|nanoITO). FTO|nanoITO electrodes were functionalized with vinyltrimethoxysilane (VTMS) to introduce vinyl groups on the electrode surfaces by silane attachment, followed by surface electropolymerization of the vinylderivatized complex, [RuII(Mebimpy)(dvbpy)(OH2)]2+ (12+; Mebimpy: 2,6-bis(1-methyl-1H-benzo[d]imidazol-2-yl)pyridine; dvbpy: 5,5'- divinyl-2,2'-bipyridine), in a mechanism dominated by a graftingthrough method. The surface coverage of catalyst 12+ was controlled by the number of electropolymerization cycles. The combined silane attachment/cross-linked polymer network stabilized 12+ on the electrode surface under a variety of conditions especially at pH > ~6. Surface-grafted poly12+ was stable toward redox cycling at pH ~7.5 over an ~4-h period. Sustained heterogeneous electrocatalytic water oxidation by the electrode gave steady-state currents for at least ~6 h with a Faradaic efficiency of ~68% for O2 production. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting is a promising way for renewable energy conversion and storage, but efficient and low cost catalysts are essential mainly due to the sluggish oxygen evolution reaction (OER). Here, hierarchical Cu/Co selenide nanotubes assembled of nanosheets were successfully prepared. Benefiting from the rich active sites, highly exposed surface and enhanced charge transport, excellent electrocatalytic performance with a considerably low overpotential (238 mV at 10 mA cm−2), fast reaction kinetics (Tafel slop: 62 mV dce−1) and outstanding durability was achieved. Based on the ex‐situ characterizations, in‐situ formed (oxy)hydroxides were confirmed, which are presumably the intrinsic electrocatalytic sites for OER. Hierarchical Co/Cu selenide nanotubes assembled of nanosheets are successfully constructed. Benefiting from rich active sites, highly exposed surface, enhanced charge transport and bimetallic synergistic effects, highly efficient electrocatalytic performance towards OER with a low overpotential (238 mV at 10 mA cm−2), fast reaction kinetics (tafel slop: 62 mV dce−1) and outstanding durability) is achieved, even exceeding that of commercial IrO2. [ABSTRACT FROM AUTHOR]

In situ Raman and in situ EPR spectroscopy in combination with electrochemistry have been used to investigate the behavior of mixed cobalt nickel and cobalt copper oxides in the oxygen evolution reaction (OER). All experiments were carried out in homemade electrochemical cells using 0.1 M KOH as the electrolyte. The OER activities vary depending on the annealing conditions of the catalyst precursors, also reflected by different behaviours during the in situ spectroscopic experiments. The different activity of the Co/Ni oxides is most likely related to the formation of either γ- or β-NiO(OH), characterized by distinct features in the Raman spectra. Thus, a higher percentage of β-NiO(OH) is present in the more active catalyst. A different behaviour of Co/Cu catalysts has been shown by in situ Raman spectroscopy too, but the active phase could not be identified because of missing spectral features. However, in situ EPR spectroscopy revealed the partial dissolution of Cu(II), suggesting the formation of a Co-enriched oxide/hydroxide surface. [ABSTRACT FROM AUTHOR]

A novel series of bridging ligands and their Ru II photosensitizer–catalyst dyads have been prepared and characterized by NMR and electronic absorption spectroscopy as well as cyclic voltammetry. The presence of asymmetry in the ligands facilitated selective metal coordination, which greatly enhanced the ease of the preparation of the dyads. The photophysical properties of the photosensitizers and the photosensitizer–catalyst dyads were also studied. All the photosensitizers were found to be strong emitters while the extremely weak emission of the dyads suggested quenching by either energy or electron transfer. The water oxidation activities of the dyads have been evaluated under both light and Ce IV activated conditions. The dyads were found to be active under Ce IV activated conditions. Electrochemical studies also suggest that these systems may be used as electrocatalysts for photoelectrochemical water oxidation. [ABSTRACT FROM AUTHOR]

In this work, biopolymers like chitosan and Bovine Serum Albumin (BSA) templated and ionic liquid (IL)-driven synthesis of crystalline NiO nanoparticles for ultrafast room temperature detection of ammonia together with its semi-empirical mechanistic details are reported. The XRD results have revealed the crystalline nature of synthesized NiO nanoparticles; the contact angle measurements for the adhesive nature of the NiO nanoparticles have been carried out and the films have been subjected to gas sensing studies by chemo-resistive method. The as-prepared BSA templated ionic liquid driven NiO based thin film sensor displays an ultrafast response for the room temperature detection of ammonia with an excellent response and recovery times of 38 and 13 s, respectively, towards a lower detection limit up to 1 ppm. The ultrafast sensing mechanism of the ammonia has been deduced with the aid of X-ray Photoelectron Spectroscopy (XPS) analysis. Furthermore, as-synthesized BSA/BSA-IL templated NiO electrodes have displayed excellent electrocatalytic water oxidation in alkaline media, with a collective water-splitting stable current density of 10 mA∙cm−2. We have observed the HOMO-LUMO gap and the Valence Band/Conduction Band (VB/CB) position from the Bredas method calculations which clarifies the highest aptitude of NiO prepared with BSA-IL template for superfast ammonia gas sensing as the CB energy is significantly lower than that of NiO synthesized via the BSA template. The dual approach of multifarious applications for the ultrafast ammonia sensing and the corresponding electrochemical water oxidation through the bio-inspired NiO-nanoparticles is in fact one of the novel applications being cited in this paper. The results highlight the grave implications of as-synthesized NiO-nanoparticles as a brilliant cost-effective gas sensor and as an effective alternative electrode for sustainable energy harvesting. [Display omitted] • NiO nanomaterial synthesisized from biodegradable polymers and green solvent ionic liquid. • Ultrafast sensing of ammonia at room temperature by ionic liquid driven NiO. • Ionic liquid driven NiO shows excellent water oxidation reaction. • Evaluated the semi-empirical mechanistic details for ultrafast sensing of NiO. [ABSTRACT FROM AUTHOR]

Homogeneous and heterogeneous materials are attractive electrochemical reaction catalysts, specifically metal-nitrogen-carbon (M-N x -C) organic-based molecular materials are emerged as the most promising candidates. However, efficiently producing M-N x -C organic-based nanosheets for solving the poor activity of bulk-phase catalysts remains a significant challenge. Herein, we put forward a first concept of semi-homogeneous molecular catalysts, through producing 2D metal-polyphthalocyanine (M-PPc) nanosheet with the superiority of hetero/homogeneous via an electrochemical delamination to achieve bridging from hetero to homogeneous. Multi-step ex-situ characterizations and theoretical simulations reveal a novel mechanism of electrochemical stripping, named as electron-coupled transalkylation, where occurs transalkylation, site-to-site transalkylation, and hydrocarbon evolution reactions accompanied by the transformation of intermediates from B-Ni 1.0 Fe 0.3 PPc, (TBA+) x ·B-Ni 1.0 Fe 0.3 PPc, x*(C 4 H 9) x ·B-Ni 1.0 Fe 0.3 PPc, to final product of Ni 1.0 Fe 0.3 PPc NSs, realizing the eventual delamination. The semi-homogeneous Ni 1.0 Fe 0.3 PPc NSs delivers a lower overpotential of 269 mV to reach 10 mA cm-2 than benchmark RuO 2 and maintains superior stability for oxygen evolution. DFT calculations unveil that the NiN 4 double sites of Ni 1.0 Fe 0.3 PPc NSs acted as real catalytic centres not only reduce the energy barrier of reaction process, but also accelerate adsorption of intermediates and desorption of oxygen molecules, thus boosting the oxygen evolution kinetics. [Display omitted] • Electrochemically exfoliated 2D electrocatalysts realizing the bridging between homogeneous and heterogeneous. • Exfoliating 2D organometallic framework-based materials via electrochemical exfoliation. • Novel electrochemical exfoliation mechanism of electron-coupled transalkylation. • Semi-homogeneous two-dimensional nanosheet catalyst with superior oxygen evolution reaction performance. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) not only combine globally demanded renewable energy generation and environmental remediation onto a single platform but also rationalize structure-performance synergies to devise smarter materials with remarkable performance. The robust and non-interpenetrated cationic MOF exemplifies a unique bifunctional scaffold for the efficient electrochemical oxygen evolution reaction (OER) and ultrasensitive monitoring of biohazards. The microporous framework containing Brønsted acid-functionalized [Co 2 (μ 2 -OH)(CO 2 ) 2 ] secondary building units (SBUs) exhibits remarkable OER performance in 1 M KOH, requiring 410 mV overpotential to obtain 10 mA cm -2 anodic current density, and a low Tafel slope of 55 mV/dec with 93.1% Faradaic efficiency. Apart from the high turnover frequency and electrochemically assessable surface area, steady OER performance over 500 cycles under potentiodynamic and potentiostatic conditions result in long-term catalyst durability. The highly emissive attribute from nitrogen-rich fluorescent struts benefits the MOF in recyclable and selective fluoro-detection of three biothiols (l-cysteine, homocysteine, and glutathione) in water with a fast response time. In addition to colorimetric monitoring in the solid and solution phases, control experiments validate size-exclusive biothiol speciation through molecular-dimension-mediated pore diffusion. The role of SBUs in the OER mechanism is detailed from density functional theory-derived free energy analysis, which also validates the importance of accessible N-sites in sensing via portraying framework-analyte supramolecular interactions.

The sluggish anodic water oxidation reaction is synergistically activated over fishnet-like superstructures constructed from ultrafine and ultralong Ni-MOF nanowire arrays directionally grown on highly rough and conductive scaffolds. • In water electrolysis, the anodic water oxidation needs much higher overpotential than cathodic water reduction. • The Fishnet-like superstructures constructed from ultrafine and ultralong Ni-MOF nanowire arrays on highly rough and conductive scaffolds can synergistically deliver efficient and robust alkaline water oxidation activity. • A η 10 of 240 mV is maintained after a long-term durability test for as long as 32 h. The water oxidation efficiency driven by electrocatalysts is related to the energy conversion efficiency of water electrolysis and other systems. It is the key to expose active sites as possible, to fully and firmly contact with other components, and to deliver superior conductivity for the development of high-performance electrocatalysts. Herein, we have fabricated self-supporting Ni-MOF electrode containing three-dimensional (3D) fishnet-like superstructures, which are constructed from in-situ growth of amorphous or poor crystalline Ni-MOF nanowire arrays on highly rough and conductive scaffolds of metallic Ni/carbon cloth (Ni-MOF/Ni/CC). The Ni-MOF/Ni/CC electrode delivers an overpotential of 250 mV at the current density of 10 mA cm−2 (η 10). The η 10 is maintained at 240 mV after a constant current electrolysis for 32 h, which is much smaller than those of Ni-MOF/CC (423 mV) and Ni/CC (281 mV). The superior activity and robust durability can be attributed to the synergistic activating effect of each component in the superstructures with high density of coordination unsaturated active sites, intimate connection and excellent conductivity. This work can provide a new strategy to develop high-efficiency MOFs-based electrocatalysts for electrocatalytic water oxidation. [ABSTRACT FROM AUTHOR]

• Polyoxometalate supported copper dimeric complexes. • Crystal structure analysis. • Spectral analysis. • Electrocatalytic water oxidation and reduction. • Electrocatalytic hydrogen peroxide reduction. A polyoxometalate (POM) supported copper dimeric complex, [Mo 8 O 26 {Cu 2 (2,2′-bpy) 2 (CH 3 COO) 2 H 2 O} 2 ]٠H 4 Mo 8 O 26 ·16H 2 O (1) has been synthesized using conventional wet synthesis. The compound has been characterized using routine spectral techniques and its molecular structure has been elucidated using single crystal X-ray crystallography. The two copper(II) ions are bridged by acetate ions and each copper ion is also coordinated to 2,2′-bipyridine molecule. In each dimer, one of the copper ions is bonded to the POM anion from one side, whereas the other copper ion is bonded to a water molecule, hence acquiring a penta-coordinated square pyramidal structure around each copper center. The lattice water molecules play an important role to stabilize the system, by forming a water pentamer, which binds both the polyoxometalate supported transition metal complex and the other POM anion [Mo 8 O 26 ]4–. Interestingly, compound 1 is found to function as a versatile heterogeneous electro-catalyst for water oxidation, proton reduction and hydrogen peroxide reduction. [ABSTRACT FROM AUTHOR]