Three-Dimensional Porous Indium Single-Atom Catalysts with Improved Accessibility for CO2 Reduction to Formate.

Single-atom catalysts (SACs) present substantial potential in electrocatalytic CO2 reduction reactions; however, inferior accessibility of single-atom sites to CO2 limits the overall CO2RR performances. Herein, we propose to improve the accessibility between In sites and CO2 through the construction of a three-dimensional (3D) porous indium single-atom catalyst (In1/NC-3D). The NaCl template-mediated synthesis strategy generates the unique 3D porous nanostructure of In1/NC-3D. Multiple characterizations validate that In1/NC-3D exhibits increased exposure of active sites and enhanced CO2 transport/adsorption capacity compared to the bulk In1/NC, thus improving accessibility of active sites to CO2. As a result, the In1/NC-3D presents superior CO2RR performance to the bulk In1/NC, with a partial current density of formate of 67.24 mA cm-2 at -1.41 V, relative to a reversible hydrogen electrode (vs RHE). The CO2RR performances with high formate selectivity at a large current density also outperform most reported In-based SACs. Importantly, the In1/NC-3D is demonstrated to maintain an FEformate of >82% at -66.83 mA·cm-2 over 21 h. This work highlights the design of a 3D porous single-atom catalyst for efficient CO2RR, promoting the development of advanced catalysts toward advanced energy conversion.

Regulating the N-Coordination Structure of Fe-Fe Dual Sites as the Electrocatalyst for the O2 Reduction Reaction in Metal-Air Batteries.

Iron-nitrogen coordinated catalysts are regarded as efficient catalysts for the oxygen (O2) reduction reaction (ORR), wherein the coordination environment of Fe sites is critical to the catalytic activity. Herein, we explored the effect of the nitrogen-coordination structure of dual-atomic Fe2 sites (i.e., Fe2-N6-C and Fe2-N4-C) on the performance of the ORR. The half-wave potential (E1/2) of Fe2-N6-C is 0.880 V vs RHE, outperforming that of the tetracoordinate Fe2-N4-C (0.851 V) and commercial Pt/C (0.850 V) in alkaline electrolytes. The Fe2-N6-C-based zinc-air battery delivers a maximum power density of (258.6 mW/cm2) and superior durability under 10 mA/cm2. Theoretical calculations unveil that the moieties of Fe2-N6 profits the d-electron rearrangement of the Fe2 sites. The electronic and geometrical structure of Fe2-N6 promotes the O2 molecules adsorbed on the Fe2 site and reduces the dissociation energy barrier of O2, benefiting fracture of O-O bonds and acceleration of the transformation of O2 to *OOH (the first step of the ORR process). Such exploration of modulating the local N-coordination environment of Fe2 dimers paves an in-depth insight to design and optimize dual-atomic catalysts.

Synergistic impacts of Fe/Fe3C and Fe-Nx on high-efficiency microwave-absorbing properties of Fe/Fe3C@NC composites.

The construction of multi-component composites has become an attractive strategy for high-performance microwave absorption through balancing the magnetic and dielectric loss. However, the influences of different components on absorption performance are ambiguous, which has inevitably hampered the widespread applications of microwave absorbents. Herein, we rationally designed the multi-component absorbers of N-doped carbon composited with Fe/Fe3C nanoparticles, and systematically investigated the impacts of Fe/Fe3C nanoparticles and Fe-Nxmoieties on the microwave-absorbing capacities. It is found that the coexisitence of Fe/Fe3C and Fe-Nxis indispensable to realize the strong microwave absorption ability by simultaneously enhancing the dielectric and magnetic loss in the frequency range of 2-18 GHz. As expected, our optimal absorber dispersed in paraffin with a filler loading of 15 wt% exhibits the minimum reflection loss (RLmin) value of -49 dB and the maximum effective absorption bandwidth (BWeff) value of 4.2 GHz at a low thickness. Our work specifies the importance and influence of the coexistence between the Fe-Nxconfigurations and Fe/Fe3C nanoparticles in the carbon-based composites for the superior microwave absorption and inspires the future fabrication of extraordinary materials in the electromagnetic field.

Accelerating CO2 Electroreduction to Multicarbon Products via Synergistic Electric-Thermal Field on Copper Nanoneedles.

Electrochemical CO2 reduction is a promising way to mitigate CO2 emissions and close the anthropogenic carbon cycle. Among products from CO2RR, multicarbon chemicals, such as ethylene and ethanol with high energy density, are more valuable. However, the selectivity and reaction rate of C2 production are unsatisfactory due to the sluggish thermodynamics and kinetics of C-C coupling. The electric field and thermal field have been studied and utilized to promote catalytic reactions, as they can regulate the thermodynamic and kinetic barriers of reactions. Either raising the potential or heating the electrolyte can enhance C-C coupling, but these come at the cost of increasing side reactions, such as the hydrogen evolution reaction. Here, we present a generic strategy to enhance the local electric field and temperature simultaneously and dramatically improve the electric-thermal synergy desired in electrocatalysis. A conformal coating of ∼5 nm of polytetrafluoroethylene significantly improves the catalytic ability of copper nanoneedles (∼7-fold electric field and ∼40 K temperature enhancement at the tips compared with bare copper nanoneedles experimentally), resulting in an improved C2 Faradaic efficiency of over 86% at a partial current density of more than 250 mA cm-2 and a record-high C2 turnover frequency of 11.5 ± 0.3 s-1 Cu site-1. Combined with its low cost and scalability, the electric-thermal strategy for a state-of-the-art catalyst not only offers new insight into improving activity and selectivity of value-added C2 products as we demonstrated but also inspires advances in efficiency and/or selectivity of other valuable electro-/photocatalysis such as hydrogen evolution, nitrogen reduction, and hydrogen peroxide electrosynthesis.

Tuning Active Species in N-Doped Carbon with Fe/Fe3C Nanoparticles for Efficient Oxygen Reduction Reaction.

Transition metal-nitrogen-carbon (M-N-C) catalysts (M = Fe, Co, etc.) are the most promising substituents of Pt-based catalysts for oxygen reduction reaction (ORR). However, the insufficient active species in catalysts inevitably hamper their widespread applications. Herein, we report the regulation of the active species in the catalysts of multicomponent N-doped carbon with Fe/Fe3C nanoparticles by polydopamine (PDA) coating. It is found that the PDA is conducive to increasing the pyridinic, graphitic, and total N content in the carbon matrix. Benefiting from the chelating effects, the PDA further profits the formation of Fe-Nx structures and the implantation of Fe/Fe3C nanoparticles in the matrix during the pyrolysis. As expected, the resultant catalysts exhibit over 15 times mass activity toward ORR than nitrogen-doped carbon. Moreover, our developed catalysts show long-term stability as well as high methanol tolerance, which is superior to that of the commercial Pt/C electrode. This work provides a new avenue to explore a wider range of high-performance ORR electrocatalysts by regulating the active species.

Hydroxyl/amino and Fe(III) co-grafted graphite carbon nitride for photocatalytic removal of volatile organic compounds.

Hydroxyl/amino and Fe(III) co-grafted graphite carbon nitride (CN) is fabricated via alkaline hydrothermal treatment and followed by an impregnation adsorption process. In this unique fabrication, hydroxyl and amino groups enriched on the surface play a vital role in improving the adsorption capacity for volatile organic compounds (VOCs), while the grafted amorphous Fe(III) clusters could dominantly regulate the path of molecular oxygen activation via photo-Fenton reaction, and change the selectivity of intermediate reactive oxygen species (ROS) with the assistant of the rich surficial hydroxyl groups. Meanwhile, both the grafted functional groups and Fe(III) clusters can serve as photogenerated charge acceptors for collaboratively accelerating carriers' separation. Besides, the Fe(III)-mediated interfacial charge transfer effect (IFCT) also could extend visible light absorption and boost carriers' generation. Benefiting from the virtues of the complementary and synergy of the grafted hydroxyl/amino and Fe(III), the dual-functionalized CN is qualified as an efficient photocatalyst for removal of VOCs, which exhibits 22 and 18 times isopropanol (IPA) adsorption capacity and CO2 production than of pristine CN during photocatalytic IPA removal, respectively. Moreover, this work provides a new strategy of surficial group-cluster bifunctionalization for systematically improving sustainable solar-to-chemical energy conversion towards VOCs mineralization.

Atomically Dispersed s-Block Magnesium Sites for Electroreduction of CO2 to CO.

Atomically dispersed transition metal sites have been extensively studied for CO2 electroreduction reaction (CO2 RR) to CO due to their robust CO2 activation ability. However, the strong hybridization between directionally localized d orbits and CO vastly limits CO desorption and thus the activities of atomically dispersed transition metal sites. In contrast, s-block metal sites possess nondirectionally delocalized 3s orbits and hence weak CO adsorption ability, providing a promising way to solve the suffered CO desorption issue. Herein, we constructed atomically dispersed magnesium atoms embedded in graphitic carbon nitride (Mg-C3 N4 ) through a facile heat treatment for CO2 RR. Theoretical calculations show that the CO desorption on Mg sites is easier than that on Fe and Co sites. This theoretical prediction is demonstrated by experimental CO temperature program desorption and in situ attenuated total reflection infrared spectroscopy. As a result, Mg-C3 N4 exhibits a high turnover frequency of ≈18 000 per hour in H-cell and a large current density of -300 mA cm-2 in flow cell, under a high CO Faradaic efficiency ≥90 % in KHCO3 electrolyte. This work sheds a new light on s-block metal sites for efficient CO2 RR to CO.

Bismuth(III)-Doped NaYbF4:Tm3+ Fluorides with Highly Efficient Upconversion Emission under Low Irradiance.

Concentration quenching of upconversion (UC) luminescence (UCL) is a common phenomenon in rare-earth-doped materials that seriously restricts the concentration of the activator and sensitizer and withholds their UC emissions and quantum yields. In particular, it remains a tremendous challenge to develop one novel strategy based on the introduction of trivalent bismuth (Bi3+) ions to exceed the typical thulium (Tm3+) ion concentration and reach high-efficiency UC under low illumination. In this work, the Tm3+ accommodation capacity can be increased from 2.0 to 8.0 mol % in NaYbF4:Tm3+ materials with the assistance of Bi3+ ions, which maintains strong UC emissions with large absolute UC quantum yields under low illumination. Specifically, the total upconversion quantum yield (UCQY) of the as-obtained Na(Tm0.08Yb0.60Bi0.32)F4 (8Tm60Yb32Bi) sample can reach as high as 1.45% upon continuous-wave (CW) laser excitation at 40 W cm-2. Strikingly, the total UCQY still remains at a high level (0.41%) even though the CW power density decreases to 1.5 W cm-2. Moreover, the intrinsic mechanism of the breakthrough in the threshold of concentration quenching of UCL by Bi3+ ions was also fully explored. These advances in enhancing UC emissions and UCQYs under a low pump power density offer exciting opportunities for important photonic applications.

Photoelectrochemical detection of breast cancer biomarker based on hexagonal carbon nitride tubes.

Photoelectrochemical (PEC) sensor for sensitive detection of breast cancer biomarker human epidermal growth factor receptor 2 (HER2) utilizing hexagonal carbon nitride tubes (HCNT) as photoactive material is reported. The detection is based on suppression of the PEC current intensity of the sensor. HCNT were synthesized via a facile hydrothermal method with large specific surface area and low electron-hole recombination. Au nanoparticles (AuNPs) were deposited onto the surface of the HCNT, which enhanced the photocurrent intensity of the HCNT by one time. For HER2 detection, peptide specific to HER2 was immobilized on the AuNPs surface for capturing HER2 molecules. The following binding of HER2 with HER2 aptamer and the reaction of phosphate groups on aptamer with molybdate can form molybdophosphate precipitate, which sticks to the surface of HCNT and impedes electron transport. Thus, photocurrent intensity of the sensor was suppressed. Under optimal conditions, the linear relationship between the PEC intensity and the logarithm of HER2 concentration was from 0.5 to 1 ng mL-1 with low limit of detection (LOD) of 0.08 pg mL-1. Furthermore, the PEC sensor also displayed capability for detecting HER2 in human serum samples. This PEC sensor signal detection strategy can be easily adapted to other PEC sensors involving DNA and find wide applications. Graphical abstract.

A porous carbon nitride modified with cobalt phosphide as an efficient visible-light harvesting nanocomposite for photoelectrochemical enzymatic sensing of glucose.

A porous carbon nitride (PCN) modified with cobalt phosphides (CoP) was synthesized. In this nanocomposite, the CoP (in different weight fractions) serves (a) as the electron acceptor to accelerate the photoinduced charge separation, and (b) as the photosensitizer to increase the photoelectrochemical (PEC) response to visible light. Dissolved oxygen acts as the electron acceptor to generate PEC current. If glucose oxidase (GOx) catalyzes the oxidation of glucose, dissolved oxygen is consumed. This leads to the suppression of photocurrent. The photocathode biosensor has a linear response in the 0.05 to 0.7 mM glucose concentration range and a 1.1 µM limit of detection. Graphical abstractSchematic of a photoelectrochemical glucose biosensor based on the use of cobalt phosphide-modified porous carbon nitrides. PCN: porous carbon nitride; CoP: cobalt phosphide.

Controllable Interlayer Spacing of Sulfur-Doped Graphitic Carbon Nanosheets for Fast Sodium-Ion Batteries.

The electrochemical behaviors of current graphitic carbons are seriously restricted by its low surface area and insufficient interlayer spacing for sodium-ion batteries. Here, sulfur-doped graphitic carbon nanosheets are reported by utilizing sodium dodecyl sulfate as sulfur resource and graphitization additive, showing a controllable interlayer spacing range from 0.38 to 0.41 nm and a high specific surface area up to 898.8 m2 g-1 . The obtained carbon exhibits an extraordinary electrochemical activity for sodium-ion storage with a large reversible capacity of 321.8 mAh g-1 at 100 mA g-1 , which can be mainly attributed to the expanded interlayer spacing of the carbon materials resulted from the S-doping. Impressively, superior rate capability of 161.8 mAh g-1 is reserved at a high current density of 5 A g-1 within 5000 cycles, which should be ascribed to the fast surface-induced capacitive behavior derived from its high surface area. Furthermore, the storage processes are also quantitatively evaluated, confirming a mixed storage mechanism of diffusion-controlled intercalation behavior and surface-induced capacitive behavior. This study provides a novel route for rationally designing various carbon-based anodes with enhanced rate capability.

Constructing hierarchical sulfur-doped nitrogenous carbon nanosheets for sodium-ion storage.

Hierarchical sulfur-doped nitrogenous carbon (S/NC) and nitrogenous carbon (NC) nanosheets are successfully fabricated by carbonization of their corresponding precursor polymers which are synthesized through the polymerization reaction of dianhydride and multi-amine compounds. Hierarchical S/NC nanosheets deliver greatly enhanced reversible capacity, compared with hierarchical NC nanosheets, of 280 mAh g-1 at a current density of 100 mA g-1 after 300 cycles. It is found that the introduction of sulfur species in carbon skeleton results in increasing the turbostratic structures, rather than enlarging the interlayer distances, for boosting the specific capacity of sodium-ion storage. The turbostratic structures and sulfur dopant existed in the carbon can offer more active sites for the sodium-ion storage. Carbon-based materials doped with sulfur are capable of improving the sodium-ion storage property, which can broaden the horizon of designing a string of outstanding carbon materials for the future energy storage technologies.

[Bactericidal Activity of Constructed Recombinant Fusion Protein Pheromonicin-CT].

OBJECTIVE: To construct engineering peptide pheromonicin-Clostrzaum tretant krn-ui), and to test its bactericidal activity. METHODS: We amplified the gene of variable regions from hybridoma cells which secreted monoclonal antibody (mAb) against antigen in the membrane of Clostridium tetani and linked the small antibody mimetic to the channel-forming domain of colicin Ia to create Ph-CT. The Ph-CT was purified by CM sepharose ion-exchange column. Its in vitro antibacterial activity was evaluated by colony culture with different doses of Ph-CT (final concentration 2, 4, 8, and 16 microg/mL,respectively). Then we inoculated culture medium with CT strains and different doses of Ph-CT (final concentration of 4 and 16 microg/mL). The in vivo antibacterial activity of Ph-CT was evaluated by cumulative survival of mice. After 16 hours' anaerobic culture, the mice was treated with filtered CT medium or CT medium. RESULTS: We constructed Ph-CT successfully. CT colonies appeared in the CT medium treated with Ph-CT (2, 4 microg/mL), while no colony appeared in the CT medium treated with Ph-CT (8, 16 microg/mL). All mice survived when they were injected with filtered CT medium treated with Ph-CT (4, 16 microg/mL) and CT medium treated with Ph-CT (16 microg/mL). Three (50%) mice survived when they were injected with CT medium treated with Ph-CT (4 microg/mL). All mice in the control groups died after CT infections. CONCLUSION: Ph-CT may be of value as antibiotics against Clostridium tetani.

Mn Single-Atom Tuning Fe-N-C Catalyst Enables Highly Efficient and Durable Oxygen Electrocatalysis and Zinc-Air Batteries.

Fe-N-C catalyst is one of most promising candidates for oxygen electrocatalysis reaction in zinc-air batteries (ZABs), but achieving sustained high activity is still a challenging issue. Herein, we demonstrate that introducing Mn single atoms into Fe-N-C (Mn1@Fe-N-C/CNTs) enables the realization of highly efficient and durable oxygen electrocatalysis performance and application in ZABs. Multiple characterizations confirm that Mn1@Fe-N-C/CNTs is equipped with Mn-N2O2 and Fe-N4 sites and Fe nanoparticles. The Mn-N2O2 sites not only tune the electron structure of Fe-Nx sites to enhance intrinsic activity, but also scavenge the attack of radicals from Fe-Nx sites for improvement in ORR durability. As a result, Mn1@Fe-N-C/CNTs exhibits enhanced ORR performance to traditional Fe-N-C catalysts with high E1/2 of 0.89 V vs reversible hydrogen electrode (RHE) and maintains ORR activity after 15 000 CV. Impressively, Mn1@Fe-N-C/CNTs also presents excellent OER activity and the difference (ΔE) between E1/2 of ORR and OER potential at 10 mA cm-2 (Ej10) is only 0.59 V, outperforming most reported catalysts. In addition, the maintainable bifunctional activity of Mn1@Fe-N-C/CNTs is demonstrated in ZABs with almost unchanged cycle voltage efficiency up to 200 h. This work highlights the critical role of Mn single atoms in enhancing ORR activity and stability, promoting the development of advanced catalysts.

A review of the phosphorus removal of polyphosphate-accumulating organisms in natural and engineered systems.

Increasing eutrophication has led to a continuous deterioration of many aquatic ecosystems. Polyphosphate-accumulating organisms (PAOs) can provide insight into the human response to this challenge, as they initiate enhanced biological phosphorus removal (EBPR) through cyclical anaerobic phosphorus release and aerobic phosphorus uptake. Although the limiting environmental factors for PAO growth and phosphorus removal have been widely discussed, there remains a gap in the knowledge surrounding the differences in the type and phosphorus removal efficiencies of natural and engineered PAO systems. Furthermore, due to the limitations of PAOs in conventional wastewater treatment environments, there is an urgent need to find functional PAOs in extreme environments for better wastewater treatment. Therefore, it is necessary to explore the effects of extreme conditions on the phosphorus removal efficiency of PAOs as well as the types, sources, and characteristics of PAOs. In this paper, we summarize the response mechanisms of PAOs, denitrifying polyphosphate-accumulating organisms (D-PAOs), aerobic denitrifying polyphosphate-accumulating organisms (AD-PAOs), and sulfur-related PAOs (S-PAOs). The mechanism of nitrogen and phosphorus removal in PAOs is related to the coupling cycles of carbon, nitrogen, phosphorus, and sulfur. The genera of PAOs differ in natural and engineered systems, but PAOs have more diversity in aquatic environments and soils. Recent studies on the impact of several parameters (e.g., temperature, carbon source, pH, and dissolved oxygen) and extracellular polymer substances on the phosphorus removal efficiency of PAOs in natural and engineered systems are further discussed. Most of the PAOs screened under extreme conditions still had high phosphorus removal efficiencies (>80.0 %). These results provide a reference for searching for PAOs with different adaptations to achieve better wastewater treatment.

Energy-level matching of Fe(III) ions grafted at surface and doped in bulk for efficient visible-light photocatalysts.

Photocatalytic reaction rate (R) is determined by the multiplication of light absorption capability (α) and quantum efficiency (QE); however, these two parameters generally have trade-off relations. Thus, increasing α without decreasing QE remains a challenging issue for developing efficient photocatalysts with high R. Herein, using Fe(III) ions grafted Fe(III) doped TiO2 as a model system, we present a novel method for developing visible-light photocatalysts with efficient R, utilizing the concept of energy level matching between surface-grafted Fe(III) ions as co-catalysts and bulk-doped Fe(III) ions as visible-light absorbers. Photogenerated electrons in the doped Fe(III) states under visible-light efficiently transfer to the surface grafted Fe(III) ions co-catalysts, as the doped Fe(III) ions in bulk produced energy levels below the conduction band of TiO2, which match well with the potential of Fe(3+)/Fe(2+) redox couple in the surface grafted Fe(III) ions. Electrons in the surface grafted Fe(III) ions efficiently cause multielectron reduction of adsorbed oxygen molecules to achieve high QE value. Consequently, the present Fe(III)-FexTi1-xO2 nanocomposites exhibited the highest visible-light R among the previously reported photocatalysts for decomposition of gaseous organic compounds. The high R can proceed even under commercial white-light emission diode irradiation and is very stable for long-term use, making it practically useful. Further, this efficient method could be applied in other wide-band gap semiconductors, including ZnO or SrTiO3, and may be potentially applicable for other photocatalysis systems, such as water splitting, CO2 reduction, NOx removal, and dye decomposition. Thus, this method represents a strategic approach to develop new visible-light active photocatalysts for practical uses.

Effects of estrogen and phytoestrogens on endometrial leakage in ovariectomized rats and the related mechanisms.

Phytoestrogens, a group of plant-derived non-steroidal compounds that can behave as estrogens by binding to estrogen receptors, have drawn great attention for their potentially beneficial effects on human health. However, there are few studies investigating the potential side effects of phytoestrogens on the reproductive system. The present study was to elucidate the effects of 17ß-estradiol (E2), progesterone (P4), and phytoestrogens genistein (Gen), resveratrol (Res), and phloretin (Phl) on eosinophilic infiltration of the ovariectomized rat uterus and endometrial vascular permeability, and to analyze the underlying mechanisms. The ovariectomized rats received daily subcutaneous injections of E2, E2+P4, P4, Gen, Res, Phl, or an equivalent volume of vehicle for 21 days, and sham-operated animals (Sham rats) were used as the controls. Hematoxylin-eosin staining revealed a marked increase in uterine eosinophilic infiltrations in ovariectomized rats treated with E2, E2+P4 or P4, which was associated with increased expression of vascular endothelial growth factor (VEGF), nuclear factor-κB (NF-κB), and tumor necrosis factor-α (TNF-α) proteins as determined by immunohistochemical and Western blot analysis. However, all three phytoestrogens had no markedly effect on the uterine eosinophilic infiltration and the expressions of VEGF, NF-κB, and TNF-α in the uterus of ovariectomized rats. Our data demonstrate that E2 alone or in combination with P4 increases uterine eosinophilic infiltration which is related with vascular hyperpermeability caused by VEGF, NF-κB and TNF-α, whereas phytoestrogens Gen, Res, and Phl, have no such an effect.

An engineered multidomain fungicidal peptide against plant fungal pathogens.

Fungal pathogens represent major problems for human health and agriculture. As eukaryotic organisms, fungi share some important features with mammalian cells. Therefore, current anti-fungal antibiotics often can not distinguish between fungi and mammalian cells, resulting in serious side effects in mammalian cells. Accordingly, there is strong impetus to develop antifungal alternatives that are both safe and effective. The E1 family of colicin are channel-forming bacteriocins produced by Escherichia coli, which are bactericidal only to E. coli and related species. To target the channel-forming domain of colicin to fungal cell membrane, we engineered a sexual mating pheromone of Candida albicans, α-factor pheromone to colicin Ia. A peptide was constructed consisting of an α mating pheromone of C. albicans fused to the channel-forming domain of colicin Ia to create a new fusion protein, pheromonicin-CA (PMC-CA). Indirect immunolabeling showed that the PMC-CA bound to fungal cells and inhibited growth in the laboratory and field. In the field, the protective activity of pheromonicin against rice blast disease was significantly greater, on a molar basis, than that of triazoles, tricyclazole or isoprothiolane. These results suggest that fusion peptides may be of value as fungicidal agents under agricultural conditions.

Enhanced Electron Confinement of p-Block Indium Site in Extended Macrocyclic Conjugation Boosting Oxygen Reduction to Hydrogen Peroxide.

The electrocatalytic oxygen reduction reaction via a two-electron pathway (2e- ORR) is a promising route for hydrogen peroxide (H2O2) production. However, the strong electron interaction between the metal site and oxygen-containing intermediates usually generates 4-electron ORR, limiting H2O2 selectivity. Here, combining theoretical and experimental studies, we propose to enhance the electron confinement of the indium (In) center in an extended macrocyclic conjugation system toward high-efficiency H2O2 production. The extended macrocyclic conjugation in indium polyphthalocyanine (InPPc) evokes the attenuated transfer electron ability of the In center and weakens the interaction between the s orbital of In and the p obital of OOH*, favoring protonation of OOH* to H2O2. Experimentally, the prepared InPPc catalyst exhibits a noticeable H2O2 selectivity above 90% in 0.1-0.6 V vs RHE, outperforming the counterpart InPc. Importantly, the InPPc displays a high average H2O2 production rate of 23.77 mg/cm2/h in a flow cell. This study proposes a novel strategy to engineer molecular catalysts and provides new insights into the ORR mechanism.

Highly Hydrophilic and Defective Carbon Nitride for Enhanced Photocatalytic Hydrogen Evolution.

Graphitic carbon nitride (g-C3N4), as a kind of nonmetallic low-cost photocatalyst, has great potential in photocatalytic hydrogen (H2) evolution, but its poor hydrophilicity and nonwetting extremely limit its H2 evolution efficiency. Herein, highly hydrophilic and defective g-C3N4 photocatalysts (NH3-CN-P as a representative example) have been fabricated on the basis of the strategy of joint phosphorus doping and ammonia stripping. The dopant of phosphorus prefers to occupy the C atoms bonded to -NH2 groups in the g-C3N4 skeleton, which is conducive to the formation of N defects caused by the effects of electronegativity and charge balance. Moreover, ammonia stripping plays a dual role in exposing plentiful two-dimensional defective planar structure and implanting the hydrophilic groups on the surface. As expected, the photocatalytic H2 evolution property of NH3-CN-P reaches 11.31 mmol g-1 h-1, with an apparent quantum yield of 17.9% at 420 nm, outperforming the majority of the reported g-C3N4-based photocatalysts.