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Perylenetetracarboxylic dianhydride (PTCDA) derivatives have received significant attention as molecule photocatalysts. However, the poor recyclability of molecule-type photocatalysts hinders their widespread applications. Herein, immobilization of PTCDA on Al2O3 was achieved by simply physical mixing, which not only dramatically improved their recyclability, but also surprisingly improved the reactivity. A mechanism study suggested that the photo-exited state (PTCDA*) of PTCDA could promote the oxidation of thioanisole to generate PTCDA•−, which sequentially reduces oxygen to furnish superoxide radicals to achieve the catalytic cycle. Herein, the immobilization support Al2O3 was able to facilitate the strong adsorption of thioanisole, thereby boosting the photocatalytic activity. This work provides a new insight that the immobilization of organic molecular photocatalysts on those supports with proper adsorption sites could furnish highly efficient, stable, and recyclable molecular-based heterogeneous photocatalysts. [ABSTRACT FROM AUTHOR]

The exfoliation of bulk C3N4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation‐decomposition (NID) strategy that is effective in peeling off BCN into few‐layer C3N4 (fl‐CN) with tailored thickness down to bi‐layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl‐CN, which is conducive to O2 adsorption and hence relevant chemical processes. In photocatalytic O2 reduction under visible light irradiation, the H2O2 production rate over the optimal fl‐CN‐530 catalyst is 952 μmol g−1 h−1, which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH4 can be photocatalytically oxidized by on‐site formed H2O2 and active oxygen species to generate value‐added C1 oxygenates with high selectivity of 99.2 % and record‐high production rate of 1893 μmol g−1 h−1 among the metal‐free C3N4‐based photocatalysts. [ABSTRACT FROM AUTHOR]

In this study, a nonstoichiometric roxbyite (Cu58S32) phase with nanoplate (np) and snowflake (sf) morphologies was prepared under solvothermal conditions by varying the sulfur source. The Cu58S32 (CS) was subsequently used as a host matrix as well as a copper source for the in situ construction of Cu-BDC-NH2/Cu58S32 (CSM) nanohybrid materials. The regulated growth of Cu-MOF nanoplates over the well-crystalline and radially symmetric hexagonal dendritic structure of Cu58S32 led to the formation of an n–p heterojunction with a large interfacial contact area. Comprehensive characterizations of the nanohybrids unveiled improved light harvesting properties, large electrochemically active surface areas, and synergistic charge mobilization between the constituent semiconductor materials. The surface-aligned ultrathin Cu-MOF nanosheets contained three distinct types of coordinated metal sites involving Cu-(II) dimers with a paddle wheel structure and monomeric Cu-(II) with a distorted ligand environment. The optimal CSM-(sf) hybrid displayed improved photocatalytic activity toward H2 evolution (9343 μmol g–1 h–1) and O2 reduction (2339 μmol g–1 h–1) under solar light simulation with reaction rates 14–20 times greater than pure semiconductors. The strong surface hydrophilic character, distinct morphology, and high redox ability of photogenerated electrons through the S-scheme charge transfer mechanism accounted for the improved activity of the nanohybrid materials. [ABSTRACT FROM AUTHOR]

Exploring unique single‐atom sites capable of efficiently reducing O2 to H2O2 while being inert to H2O2 decomposition under light conditions is significant for H2O2 photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single‐Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single‐Zn sites on CN, forming asymmetric Zn−N3O moiety on CN (denoted as CN/Zn−OAc), in contrast to the obtained Zn−N4 sites when sulfate (SO4) is adopted (CN/Zn−SO4). Both experimental and theoretical investigations demonstrate that the Zn−N3O moiety exhibits higher intrinsic activity for O2 reduction to H2O2 than the Zn−N4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O2 and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H2O2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn−OAc catalyst exhibits significantly improved photocatalytic H2O2 production activity under visible light irradiation. [ABSTRACT FROM AUTHOR]

Developing highly efficient catalytic sites for O2 reduction to H2O2, while ensuring the fast injection of energetic electrons into these sites, is crucial for artificial H2O2 photosynthesis but remains challenging. Herein, we report a strongly coupled hybrid photocatalyst comprising polymeric carbon nitride (CN) and a two‐dimensional conductive Zn‐containing metal–organic framework (Zn‐MOF) (denoted as CN/Zn‐MOF(lc)/400; lc, low crystallinity; 400, annealing temperature in °C), in which the catalytic capability of Zn‐MOF(lc) for H2O2 production is unlocked by the annealing‐induced effects. As revealed by experimental and theoretical calculation results, the Zn sites coordinated to four O (Zn‐O4) in Zn‐MOF(lc) are thermally activated to a relatively electron‐rich state due to the annealing‐induced local structure shrinkage, which favors the formation of a key *OOH intermediate of 2e− O2 reduction on these sites. Moreover, the annealing treatment facilitates the photoelectron migration from the CN photocatalyst to the Zn‐MOF(lc) catalytic unit. As a result, the optimized catalyst exhibits dramatically enhanced H2O2 production activity and excellent stability under visible light irradiation. [ABSTRACT FROM AUTHOR]

Perylenetetracarboxylic dianhydride (PTCDA) derivatives have received significant attention as molecule photocatalysts. However, the poor recyclability of molecule-type photocatalysts hinders their widespread applications. Herein, immobilization of PTCDA on Al2O3 was achieved by simply physical mixing, which not only dramatically improved their recyclability, but also surprisingly improved the reactivity. A mechanism study suggested that the photo-exited state (PTCDA*) of PTCDA could promote the oxidation of thioanisole to generate PTCDA•−, which sequentially reduces oxygen to furnish superoxide radicals to achieve the catalytic cycle. Herein, the immobilization support Al2O3 was able to facilitate the strong adsorption of thioanisole, thereby boosting the photocatalytic activity. This work provides a new insight that the immobilization of organic molecular photocatalysts on those supports with proper adsorption sites could furnish highly efficient, stable, and recyclable molecular-based heterogeneous photocatalysts.

Despite the direct utilizing metal‐organic frameworks (MOFs) as promising photocatalysts for H2O2 production, their activity and selectivity are still undesirable owing to the insufficient active centers, weak visible‐light absorption, and limited charge transfer. Herein, the Ce‐doped Ti‐based MOFs MIL‐125‐NH2 photocatalysts (Ce/TiMOFs) were synthesized by a facile impregnation‐coordination method, during which the doped Ce species could not only extend the visible‐light absorption edge but also provide new reactive sites for promoting the charge transfer and selectivity of two‐electron O2 reduction. Interestingly, the optimal Ce/TiMOFs‐0.010 achieved a rate of H2O2 yield of 2464 μM h−1 g−1 with ∼3.4‐fold improvement compared to TiMOFs, attributed to the faster conversion rate of the main reactive oxygen intermediates (⋅O2−) and improved average transfer electron number. This work provides an effective strategy to optimize the photocatalytic performances of MOFs and expands the application of MOFs in the sustainable energy production field. [ABSTRACT FROM AUTHOR]

Direct electro- and photo-synthesis of H 2 O 2 through the 2e - O 2 reduction reaction (ORR) and H 2 O oxidation reaction (WOR) offer promising alternatives for on-demand and on-site production of this chemical. Exploring robust and selective active sites is crucial for enhancing H 2 O 2 production through these pathways. Single-atom catalysts (SACs), featuring isolated active sites on supports, possess attractive properties for promoting catalysis and unraveling catalytic mechanisms. This review first systematically summarizes significant advancements in atomic engineering of both metal and nonmetal single-atom sites for electro- and photo-catalytic 2e - ORR to H 2 O 2 , as well as the dynamic behaviors of active sites during catalytic processes. Next, the progress of single-atom sites in H 2 O 2 production through 2e - WOR is overviewed. The effects of the local physicochemical environments on the electronic structures and catalytic behaviors of isolated sites, along with the atomic catalytic mechanism involved in these H 2 O 2 production pathways, are discussed in detail. This work also discusses the recent applications of H 2 O 2 in advanced chemical transformations. Finally, a perspective on the development of single-atom catalysis is highlighted, aiming to provide insights into future research on SACs for electro- and photo-synthesis of H 2 O 2 and other advanced catalytic applications., (© 2024 Wiley‐VCH GmbH.)

Abstract The direct electrochemical response of membrane‐bound human cytochrome P450 1A2 (CYP1A2) was studied on pyrolytic graphite electrodes, while encapsulated in a sol‐gel matrix. The enzymatic reduction of O2 was evaluated in the presence and absence of its electron donor partner, cytochrome P450 oxidoreductase (CPR). When used without CPR, CYP1A2 was shown to be highly sensitive to O2 even in the presence of residual amounts. Under aerobic conditions (air‐saturated solutions), the catalytic signal attributed to the reaction with O2 was lost, suggesting the enzyme was inactivated. In contrast, the CYP1A2/CPR complex retained O2 reductase activity with high O2 concentration in solution. The results demonstrated a crucial role of CPR in stabilizing the immobilized CYP1A2 enzyme and in the preservation of O2 electrocatalysis, when using this electrochemical set‐up. Though the enzyme's monooxygenase activity towards caffeine was not detected, this study highlights the complexity of coupling CYP1A2 reduction currents with substrate turnover, owing to the simultaneous electrochemical measurement of the O2 reduction reaction.

The burgeoning field of continuous glucose monitoring (CGM) for diabetes management faces significant challenges, particularly in achieving precise and stable biosensor performance under changing environmental conditions such as varying glucose concentrations and O 2 levels. To address this, we present a novel biosensor based on the electroless coupling of glucose oxidation catalyzed by flavin-dependent glucose dehydrogenase (FAD-GDH) and O 2 reduction catalyzed by bilirubin oxidase (BOD) via a redox polymer, dimethylferrocene-modified linear poly(ethylenimine), FcMe 2 -LPEI. Initial cyclic voltammetry tests confirm the colocalization of both enzymatic reactions within the potential range of the polymer, indicating an effective electron shuttle mechanism. As a result, we created a hybrid biosensor that operates at open-circuit potential (OCP). It can detect glucose concentrations of up to 100 mM under various O 2 conditions, including ambient air. This resulted from optimizing the enzyme ratio to 120 ± 10 mU BOD ·U FAD-GDH -1 ·atm O 2 -1 . This biosensor is highly sensitive, a crucial feature for CGM applications. This distinguishes it from FAD-GDH traditional biosensors, which require a potential to be applied to measure glucose concentrations up to 30 mM. In addition, this biosensor demonstrates the ability to function as a noninvasive, external device that can adapt to changing glucose levels, paving the way for its use in diabetes care and, potentially, personalized healthcare devices. Furthermore, by leveraging the altered metabolic pathways in tumor cells, this system architecture opened up new avenues for targeted glucose scavenging and O 2 reduction in cancer therapy.

Molecular catalysts capable of performing electrochemical transformations are frequently utilized in the synthesis of fuels. A common benchmark for evaluating catalysts for electrochemical reactions is overpotential (η) and minimizing η remains an active goal in catalysis. This Review details approaches for the determination of thermodynamic potentials for common fuel‐forming reactions and for the determination of electrochemical overpotential, and underscores the need to employ methods that enable meaningful comparisons between molecular catalysts. Strategies for minimizing overpotential while maintaining high activity are highlighted. [ABSTRACT FROM AUTHOR]

The direct electrochemical response of membrane‐bound human cytochrome P450 1A2 (CYP1A2) was studied on pyrolytic graphite electrodes, while encapsulated in a sol‐gel matrix. The enzymatic reduction of O2 was evaluated in the presence and absence of its electron donor partner, cytochrome P450 oxidoreductase (CPR). When used without CPR, CYP1A2 was shown to be highly sensitive to O2 even in the presence of residual amounts. Under aerobic conditions (air‐saturated solutions), the catalytic signal attributed to the reaction with O2 was lost, suggesting the enzyme was inactivated. In contrast, the CYP1A2/CPR complex retained O2 reductase activity with high O2 concentration in solution. The results demonstrated a crucial role of CPR in stabilizing the immobilized CYP1A2 enzyme and in the preservation of O2 electrocatalysis, when using this electrochemical set‐up. Though the enzyme's monooxygenase activity towards caffeine was not detected, this study highlights the complexity of coupling CYP1A2 reduction currents with substrate turnover, owing to the simultaneous electrochemical measurement of the O2 reduction reaction. [ABSTRACT FROM AUTHOR]

The exfoliation of bulk C 3 N 4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation-decomposition (NID) strategy that is effective in peeling off BCN into few-layer C 3 N 4 (fl-CN) with tailored thickness down to bi-layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO 3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl-CN, which is conducive to O 2 adsorption and hence relevant chemical processes. In photocatalytic O 2 reduction under visible light irradiation, the H 2 O 2 production rate over the optimal fl-CN-530 catalyst is 952 μmol g -1  h -1 , which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH 4 can be photocatalytically oxidized by on-site formed H 2 O 2 and active oxygen species to generate value-added C1 oxygenates with high selectivity of 99.2 % and record-high production rate of 1893 μmol g -1  h -1 among the metal-free C 3 N 4 -based photocatalysts., (© 2024 Wiley‐VCH GmbH.)

[Display omitted] • Highest stability reported so far for an enzymatic electrode in organic solvents. • It results from the combination of an engineered solvent tolerant enzyme, fine tune redox polymers and porous electrodes. • The half-life is as high as 8 days in 12.5 M methanol. • This approach could be generalized to others enzymatic systems. Organic solvent tolerant enzymes are of tremendous importance for the pharmaceutical industry in search of high added-value chemicals. However, enzymes exhibit usually weak long-term activity and stability in various media. Here, we report a general strategy allowing stabilizing and keeping enzymes active in mixed-solvent systems upon immobilization on an electrode surface. It consists in the combination of an engineered solvent-tolerant enzyme, combined with fine-tuned osmium-based redox polymers where the concentration of osmium complex has been specifically tuned to minimize its deswelling, associated with the use of porous gold electrodes. This approach is validated with bilirubin oxidase as a model system. This copper enzyme is able to oxidize a wide range of substrates, combined with the reduction of O 2 to water. While all other enzymatic systems irreversibly lose their activity and stability in the presence of 7.5 M methanol or below, this optimized enzymatic system stays functional in 12.5 M methanol with no loss in current density. It exhibits a half-life of more than 8 days, which is unprecedented in the literature. We show that this electrode can also operate in DMSO, dioxane, acetonitrile and acetone, thus opening up a very wide variety of applications in the field of bioelectrocatalysis and bioelectrosynthesis. [ABSTRACT FROM AUTHOR]

Exploring unique single-atom sites capable of efficiently reducing O 2 to H 2 O 2 while being inert to H 2 O 2 decomposition under light conditions is significant for H 2 O 2 photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single-Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single-Zn sites on CN, forming asymmetric Zn-N 3 O moiety on CN (denoted as CN/Zn-OAc), in contrast to the obtained Zn-N 4 sites when sulfate (SO 4 ) is adopted (CN/Zn-SO 4 ). Both experimental and theoretical investigations demonstrate that the Zn-N 3 O moiety exhibits higher intrinsic activity for O 2 reduction to H 2 O 2 than the Zn-N 4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O 2 and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H 2 O 2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn-OAc catalyst exhibits significantly improved photocatalytic H 2 O 2 production activity under visible light irradiation., (© 2023 Wiley-VCH GmbH.)

Metal-nitrogen doped carbon catalysts (M-N/C) with abundantly accessible M-N x sites, particularly single metal atom M-N/C (SAM-N/C), have been developed as a substitute for expensive Pt-based catalysts. These catalysts are used to increase the efficiency of otherwise sluggish oxygen reduction reactions (ORR) and hydrogen evolution reactions (HER). However, although the agglomerated metal nanoparticles are usually easy to form, they are very difficult to remove due to the protective surface-coating carbon layers, a factor that significantly hampers SAM-N/C fabrication. Herein, we report a one-step pyrolysis approach to successfully fabricate single cobalt atom Co-N/C (SACo-N/C) by using a Co2+-SCN- coordination compound as the metal precursor. Thanks to the decomposition of Co2+-SCN- compound at lower temperature than that of carbon layer deposition, Co-rich particles grow up to larger ones before carbon layers formation. Even though encapsulated by the carbon layers, it is difficult for the large Co-rich particle to be completely sealed. And thus, it makes the Co atoms possible to escape from incomplete carbon layer, to coordinate with nitrogen atoms, and to form SACo-N/C catalysts. This SACo-N/C exhibits excellent performances for both ORR (half-wave potential of 0.878 V) and HER (overpotential at 10 mA/cm2 of 178 mV), and is thus a potential replacement for Pt-based catalysts. When SACo-N/C is integrated into a Zn-O 2 battery, battery with high open-circuit voltage (1.536 V) has high peak power density (266 mW/cm2) and large gravimetric energy density (755 mA h/g Zn) at current densities of 100 mA/cm2. Thus, we believe that this strategy may offer a new direction for the effective generation of SAM-N/C catalysts. [ABSTRACT FROM AUTHOR]

A key step of denitrification, the reduction of toxic nitric oxide to nitrous oxide, is catalysed by cytochrome c‐dependent NO reductase (cNOR). cNOR contains four redox‐active cofactors: three hemes and a nonheme iron (FeB). Heme b3 and FeB constitute the active site, but the specific mechanism of NO‐binding events and reduction is under debate. Here, we used a recently constructed, fully folded and hemylated cNOR variant that lacks FeB to investigate the role of FeB during catalysis. We show that in the FeB‐less cNOR, binding of both NO and O2 to heme b3 still occurs but further reduction is impaired, although to a lesser degree for O2 than for NO. Implications for the catalytic mechanisms of cNOR are discussed. [ABSTRACT FROM AUTHOR]

To unravel the influence of the structure-activity relationship (SAR) of cyano (-C N) groups on the photocatalytic activity of polymeric carbon nitride (PCN), -C N groups were controllably introduced and finely regulated within the PCN framework in this study. The SAR between the -C N contents and hydrogen peroxide (H 2 O 2) artificial photosynthesis performance was conclusively confirmed. Comprehensive experimental characterization and theoretical calculations demonstrated that the introduced -C N accelerated the dissociation of excitons to free charge carriers. The excitons dissociation efficiency was enhanced twofold, and the adsorption and activation of O 2 molecules were strengthened, driving the two-electron O 2 reduction reaction (2e- ORR) to produce H 2 O 2. Importantly, the on-site generation of abundant reactive oxygen species during 2e- ORR by the cyanided PCN photocatalyst demonstrated its outstanding performance for the removal of multifarious emerging contaminants (ECs), including 4-hydroxybenzoic acid, aspirin, and ibuprofen, to realize sustainable water purification. [Display omitted] • The cyano groups were steadily introduced and finely tuned within PCN via adjusting the thermal condensation temperature. • The cyanided PCN accelerated the dissociation of excitons and strengthened the adsorption and activation of O 2 molecules. • On-site generation of abundant •O 2 - and H 2 O 2 ROS radicals were utilized for emerging contaminants removal. [ABSTRACT FROM AUTHOR]

Developing highly efficient catalytic sites for O 2 reduction to H 2 O 2 , while ensuring the fast injection of energetic electrons into these sites, is crucial for artificial H 2 O 2 photosynthesis but remains challenging. Herein, we report a strongly coupled hybrid photocatalyst comprising polymeric carbon nitride (CN) and a two-dimensional conductive Zn-containing metal-organic framework (Zn-MOF) (denoted as CN/Zn-MOF(lc)/400; lc, low crystallinity; 400, annealing temperature in °C), in which the catalytic capability of Zn-MOF(lc) for H 2 O 2 production is unlocked by the annealing-induced effects. As revealed by experimental and theoretical calculation results, the Zn sites coordinated to four O (Zn-O 4 ) in Zn-MOF(lc) are thermally activated to a relatively electron-rich state due to the annealing-induced local structure shrinkage, which favors the formation of a key *OOH intermediate of 2e - O 2 reduction on these sites. Moreover, the annealing treatment facilitates the photoelectron migration from the CN photocatalyst to the Zn-MOF(lc) catalytic unit. As a result, the optimized catalyst exhibits dramatically enhanced H 2 O 2 production activity and excellent stability under visible light irradiation., (© 2023 Wiley-VCH GmbH.)

Abstract Efficient, durable and low cost electrocatalysts for O 2 and CO 2 reductions are required as alternate to expensive metal based catalysts in fuel cells and in the CO 2 reduction process. Herein, we describe the synthesis of reduced graphene oxide (rGO)-nickel phthalocyanine (NiPc) composite (rGO-NiPc) as a bifunctional electrocatalyst for O 2 and CO 2 reductions. The composite material, rGO-NiPc is coated on glassy carbon (GC) electrode (GC/rGO-NiPc) and used as a low cost efficient electrocatalyst for O 2 and CO 2 reductions. The results show that the addition of rGO to NiPc increases the catalytic efficiency and electrochemical charge transfer rate of NiPc. GC/rGO-NiPc provides the low potentials, +0.25 and −0.11 V (vs RHE) for O 2 and CO 2 reductions, respectively in 0.1 M HClO 4. Kinetic interpretation based on rotating disc electrode studies provides the support for the two electron pathway for CO 2 reduction to CO in 0.1 M HClO 4. Product analysis by 13C NMR confirms CO as the CO 2 reduction product. GC/rGO-NiPc shows a facile four electron pathway for O 2 reduction which can be exploited in fuel cells, metal-air batteries, chlor-alkali electrolyzers and oxygen sensing. In addition, GC/rGO-NiPc has efficient methanol tolerance capability for O 2 reduction process which is suitable to use in fuel cells. Moreover, GC/rGO-NiPc shows the high operational stability more than an hour for both O 2 and CO 2 reductions in 0.1 M HClO 4. Graphical abstract Unlabelled Image Highlights • Reduced graphene oxide (rGO)-nickel phthalocyanine (NiPc) composite (rGO-NiPc) is prepared. • Synergistic electrocatalysis is observed between rGO and NiPc. • rGO-NiPc enhances O 2 and CO 2 reductions at low overpotential. • rGO-NiPc exhibits 4 and 2 electron pathway for O 2 and CO 2 reductions, respectively. • CO 2 is selectively reduced to CO which is confirmed by 13C NMR. [ABSTRACT FROM AUTHOR]

Abstract Aiming at Pt nanoparticle catalysts for application in polymer electrolyte membrane fuel cell (PEMFC) cathodes, which are highly active and more corrosion resistant under realistic mobile applications than common Pt/C catalysts, we have prepared and investigated Pt catalysts supported on highly stable, nanostructured composite materials containing carbon nanotubes (CNTs) and titania. TiO 2 @CNT composite materials are synthesized via sol-gel processing and subsequent Pt deposition. The physical and electrochemical properties as well as the stability of these catalysts, as determined by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), rotating ring disk electrode (RRDE) measurements and accelerated degradation tests (ADTs), were compared with those of commercial Pt/C, Pt/TiO 2 and Pt/CNT. The measurements reveal a high activity of the composite catalyst, comparable to that of the Pt/C catalyst, but an almost complete loss of ORR activity upon an ADT procedure simulating start-stop behavior. In contrast to carbon supported catalysts, where degradation is mainly associated with corrosion at high potentials, we find the titania supported catalysts to mainly suffer from the reductive treatment in the ADTs. Consequences for the use of Pt catalysts supported on reducible oxides such as TiO 2 as cathode catalysts in fuel cell applications are discussed. Graphical abstract Image 1 Highlights • Synthesis of TiO 2 covered CNTs as conductive support for Pt based ORR catalysts. • Pt/TiO 2 @CNT catalysts show an ORR activity comparable to commercial Pt/C (E-Tek). • TiO 2 support stabilizes Pt NPs against particle growth and Pt dissolution. • Under start-stop conditions TiO 2 supported catalysts show high loss of ORR activity. • Partial overgrowth of the Pt NPs by a TiO 2 layer during start-stop stability tests. [ABSTRACT FROM AUTHOR]

Abstract: The aerobic reaction between glutathione (H3A) and dirhodium(II) tetraacetate, Rh2(AcO)4 (AcO− = CH3COO−), in aqueous solution (pH 7.4) breaks up the direct RhII–RhII bond and its carboxylate framework, as evidenced by UV–Vis spectroscopy. After purifying the reaction product using size exclusion chromatography, electrospray ionization mass spectrometry (ESI-MS) of the solution showed binuclear Rh2IIIHA42- and Rh2IIIHA54- ions. Evaporation yielded a solid compound, Na2Rh2IIIHA4·7H2On, for which Rh K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy revealed ~ 2 Rh-O (2.08 ± 0.02 Å) and ~ 4 Rh-S (2.33 ± 0.02 Å) bond distances around each RhIII center, and the RhIII··RhIII distance 3.11 ± 0.02 Å, close to that in dirhodium(III) complexes with three bridging thiolates connecting Rh2III units. The 13C CPMAS NMR spectrum of the RhIII–glutathione complex showed a change ∆δC > 6 ppm in the chemical shift of the COO− signal, indicating some carboxylate coordination to the Rh(III) ions. This study shows that under aerobic conditions glutathione enables oxidation of Rh2(AcO)4 and thus reduces its antitumor efficiency.Graphical Abstract: The reaction of Rh2(AcO)4 with glutathione was investigated by ESI-MS, UV–Vis, 13C NMR and X-ray absorption spectroscopy, revealing that glutathione breaks down the carboxylate framework enabling oxidization of the Rh24+ core to Rh(III) dimeric units, bridged by three thiolates. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide as an important and green oxidant for chemical process is manufactured by the anthraquinone (AQ) process, which is an indirect synthesis method and consumes a large quantity of energy. We have reported the direct and efficient synthesis of pure H2O2 aqueous solutions by O2 and H2 fuel-cell reactions using the Co-N-C compound cathode. Catalysis of Co-N-C-compound was improved in this work. Precursors of Co-N-C compounds were prepared by impregnation of 5,10,15,20-tetrakis(phenyl)-21H, 23H-porphyrin cobalt (II) (CoTPP) on various carbon materials. Effects of carbon materials, heat-treatment temperatures, Co loadings of the precursors on the electrocatalysis for H2O2 synthesis were studied from a current density (j), a H2O2 formation rate (R(H2O2)), a H2O2 concentration (C(H2O2)) and a faradic efficiency for H2O2 formation (FE(H2O2)). The most active and effective Co-N-C electrocatalyst is Ketjen-Black supported CoTPP (0.05 Co-wt%) activated at 1023 K in He stream as denoted 0.05 wt%/CoTPP/KB(1023 K) and shows a highest C(H2O2) and FE(H2O2) of 5.5 mol dm−3 (18.7 wt%) and 55%, respectively, with a high Co turnover-frequency of 26 s−1. Effects of amounts of the 0.05 wt%/CoTPP/KB(1023 K) electrocatalyst coated on the VGCF-base cathode were studied on the H2O2 synthesis and distributions of open-circuit voltages as electromotive forces to cathode and anode over-potentials and an IR-drop (VGCF: vapor-growing carbon fiber).The 0.05wt%/CoTPP/KB(1023K) electrocatalyst was active for reduction of O2 to pure H2O2 aqueous solutions 5.5 mol dm-3 and 55 % faradic efficiency (CoTPP: 5, 10, 15, 20-tetrakis(phenyl)-21H, 23H-porphyrin cobalt (II), KB: Ketjen-Black) [ABSTRACT FROM AUTHOR]

In this Concept article we present the syntheses and application of homo and heterodinuclear 'Pacman' compounds. This architecture implies that two metal coordination fragments are brought in close vicinity to each other via a covalent linkage to either support energy transfer between the two units or cooperative transformation of a substrate. Nature has shown that the combination of metal fragments, in particular two different metals, can dramatically improve the efficiency of small molecule activation. We exemplify this strategy for the activation of water, dioxygen and carbon dioxide. Furthermore, we present artificial systems in which a positive effect on the catalytic performance because of the combination of two (different) metal centers could be observed. Thus, Pacman-type compounds are very well suited as structural and functional models for their biological counterparts. [ABSTRACT FROM AUTHOR]

We present the synthesis and structural characterization of the manganese-containing polyoxotungstate, [(Mn(H2O)3)2(H2W12O42)]6− (1), obtained by reaction of MnCl2 with six equivalents of Na2WO4 in the presence of Zn(CH3COO)2 in acetate medium (pH 4.7). This has been assessed by various techniques (FTIR, TGA, UV-Visible, XPS, elemental analysis, single crystal X-ray and electrochemistry). Single-crystal X-ray analyses showed that, in the solid state, 1 forms a 2-D network in which [H2W12O42]10− fragments are linked in pairs via Mn2+ ions, leading to linear chains of the form [(Mn(H2O)3)2(H2W12O42)]n6n−. The connection between chains occurs also via Mn2+ ions which bind [H2W12O42]10− fragments belonging to two adjacent chains, forming an infinite 2-D network. A complete electrochemical study was done in aqueous solution where 1 is stable in the pH range 1 to 6. This complex undergoes multiple electron-transfer processes that lead to the electro-generation of manganese high oxidation state species that catalyse water electro-oxidation. 1 is also effective in the electro-catalytic reduction of nitrite and dioxygen.

Single nanoparticle (NP) electrochemistry detection at a micro liquid|liquid interface (LLI) is exploited using the catalyzed oxygen reduction reaction (ORR). In this way, current spikes reminiscent of nanoimpacts were recorded, which corresponded to electrocatalytic enhancement of the ORR by Pt NPs. The nature of the LLI allows exploration of new phenomena in single NP electrochemistry. The recorded impacts result from a bipolar reaction occurring at the Pt NP straddling the LLI. O2 reduction takes place in the aqueous phase, while ferrocene hydride (Fc-H+; a complex generated upon facilitated interfacial proton transfer by Fc) is oxidized in the organic phase. Ultimately, the role of reactant partitioning, NP bouncing, or the ability of NPs to induce Marangoni effects, is demonstrated. [ABSTRACT FROM AUTHOR]

Room-temperature photocatalytic conversion of CH 4 into liquid oxygenates with O 2 /H 2 O provides an appealing route for sustainable chemical industry, which, however, suffers from poor efficiency due to the undesired carrier kinetics and low yield of reactive oxygen species of the currently available photocatalysts. Here, we report an effective surface engineering strategy where concurrent constructions of oxygen vacancies and phosphate sites on TiO 2 nanosheets address the above challenge. The surface oxygen vacancies and phosphates are respective acceptors of photogenerated electrons and holes for promoted separation and migration of charge carriers. Moreover, in addition to the facilitated activation of O 2 to • OH by electrons at oxygen vacancies, the surface phosphates also facilely adsorb H 2 O via hydrogen bonds and thus effectively transfer holes to H 2 O for enhanced • OH production, thereby boosting CH 4 conversion. As a result, compared with TiO 2 sheets with only oxygen vacancies, a 2.8 times improvement in liquid oxygenate production with near-unity selectivity is achieved by virtue of the synergy of surface oxygen vacancies and phosphate sites, together with an unprecedent quantum efficiency of 19.8% under 365 nm irradiation.