Heavy-Atom Effect Regulating Room-Temperature Phosphorescence of Organic-Inorganic Zn-Based Halides for White-Light Emission.

Organic-inorganic metal halides (OIMHs) with room-temperature phosphorescence (RTP) properties have aroused great research enthusiasm as outstanding broadband white-light emitters. Current studies on OIMHs with white-light emission were achieved via self-trapped excitons (STEs), but the unclear mechanism of STE formation is not favorable for the design of materials. In this work, zero-dimensional OIMHs composed of organic 3,4,5-trimethoxybenzylamine (TBA) and zine halide were synthesized, which enhanced the ratio of the RTP emission to the fluorescence emission from the TBA ligand. The experimental and mechanistic analyses demonstrate that the manageable RTP is mainly caused by the heavy-atom effect. In particular, by adjusting the incorporation ratio of halogen, an obvious white-light emission with a chromaticity coordinate value of (0.31, 0.33) can be achieved. This work developed a method for regulating the RTP of OIMHs with the heavy-atom effect to realize white-light emission, providing a new idea for the design of white-light emission materials.

Spatial configuration of Fe-Co dual-sites boosting catalytic intermediates coupling toward oxygen evolution reaction.

Oxygen evolution reaction (OER) is the pivotal obstacle of water splitting for hydrogen production. Dual-sites catalysts (DSCs) are considered exceeding single-site catalysts due to the preternatural synergetic effects of two metals in OER. However, appointing the specific spatial configuration of dual-sites toward more efficient catalysis still remains a challenge. Herein, we constructed two configurations of Fe-Co dual-sites: stereo Fe-Co sites (stereo-Fe-Co DSC) and planar Fe-Co sites (planar-Fe-Co DSC). Remarkably, the planar-Fe-Co DSC has excellent OER performance superior to stereo-Fe-Co DSC. DFT calculations and experiments including isotope differential electrochemical mass spectrometry, in situ infrared spectroscopy, and in situ Raman reveal the *O intermediates can be directly coupled to form *O-O* rather than *OOH by both the DSCs, which could overcome the limitation of four electron transfer steps in OER. Especially, the proper Fe-Co distance and steric direction of the planar-Fe-Co benefit the cooperation of dual sites to dehydrogenate intermediates into *O-O* than stereo-Fe-Co in the rate-determining step. This work provides valuable insights and support for further research and development of OER dual-site catalysts.

Effects of Cold Rolling Reduction Rate on the Microstructure and Properties of Cu-1.16Ni-0.36Cr Alloy after Thermo-Mechanical Treatment.

In this paper, a Cu-Ni-Cr alloy was prepared by adding a Ni-Cr intermediate alloy to copper. The effects of the cold rolling reduction rate on the microstructure and properties of the Cu-1.16Ni-0.36Cr alloy after thermo-mechanical treatment were studied. The results show that the tensile strength of the alloy increased while the electrical conductivity slightly decreased with an increase of the cold rolling reduction rate. At a rolling strain of 3.2, the tensile strength was 512.0 MPa and the conductivity was 45.5% IACS. At a rolling strain of 4.3, the strength further increased to 536.1 MPa and the conductivity decreased to 41.9% IACS. The grain size and dislocation density decreased with an increase of the reduction rate in the thermo-mechanical treatment. However, when the rolling strain reached 4.3, the recrystallization degree of the alloy increased due to an accumulation of the dislocation density and deformation energy, resulting in a slight increase in the grain size and a decrease in the dislocation density. The texture strength of the brass increased due to the induced shear band, with an increase of the cold rolling reduction rate. The reduction rate promoted a uniform distribution of nano-scale Cr precipitates and further enhanced the strength via precipitation strengthening.

Exploring effective network design for monitoring soil pH and potentially toxic elements based on geochemical surveys in economically developed area.

Periodically visiting soil monitoring sites, i.e., sampling and analysis, is recognized as one of the most important ways to monitor soil quality. However, reconciling the monitoring costs with monitoring precision of the soil monitoring network (SMN) is a key technical problem to be solved. A statistically sound method, which depends on the spatial variation in monitoring indicators, was adopted to determine the number of monitoring sites and the monitoring interval as well as their ability to detect a particular change under an economically feasible scenario. The spatial variation in soil monitoring indicators was inquired from the "Multi-Purpose Regional Geochemical Survey in Zhejiang Province (MRGSZ)" project. Based on the data for soil pH and concentration of potentially toxic elements, the number of monitoring sites and the monitoring intervals that might be used for soil monitoring were determined with the administrative region as the monitoring unit. The results showed that there was great spatial variation in the MRGSZ region, which resulted in discrepancies in the minimum detectable changes (MDCs), monitoring site numbers, and temporal monitoring intervals for revisiting. Our research proposes a number of monitoring sites (nr) that could reconcile the monitoring costs, practicability and monitoring precision; thus, it was recommended for the design of SMNs. Under nr, the MDC values of each monitoring indicator were acceptable for all administrative regions, and the temporal monitoring intervals were practical with variations of 6.7-14.8 years.

Polystyrene Waste Thermochemical Hydrogenation to Ethylbenzene by a N-Bridged Co, Ni Dual-Atom Catalyst.

Recycling waste plastics requires the degradation of plastics into small molecules. However, various products are widely distributed using traditional methods of depolymerizing polystyrene (PS) such as catalytic pyrolysis and hydrogenolysis. Here, we creatively report a N-bridged Co, Ni dual-atom (Co-N-Ni) catalyst for the targeted conversion of waste PS plastics to ethylbenzene via a pressurized tandem fixed-bed reactor where hydropyrolysis is coupled with downstream vapor-phase hydrotreatment. The Co-N-Ni catalyst achieves 95 wt % PS conversion with 92 wt % ethylbenzene yield, significantly superior to the corresponding single-atom catalysts, and enables degradation of real PS plastics. Theoretical calculations and experimental results demonstrate that the d-band center of metal atoms is well regulated in the Co-N-Ni catalyst. The Co site activates the C═C bond more easily, while the Ni site spatially optimizes the adsorption configuration of the styrene molecule due to the electronic interaction. This Co-N-Ni catalyst in the tandem reactor also shows excellent durability and provides a new direction for real plastic degradation.

Construction of Co4 Atomic Clusters to Enable Fe-N4 Motifs with Highly Active and Durable Oxygen Reduction Performance.

Fe-N-C catalysts with single-atom Fe-N4 configurations are highly needed owing to the high activity for oxygen reduction reaction (ORR). However, the limited intrinsic activity and dissatisfactory durability have significantly restrained the practical application of proton-exchange membrane fuel cells (PEMFCs). Here, we demonstrate that constructing adjacent metal atomic clusters (ACs) is effective in boosting the ORR performance and stability of Fe-N4 catalysts. The integration of Fe-N4 configurations with highly uniform Co4 ACs on the N-doped carbon substrate (Co4 @/Fe1 @NC) is realized through a "pre-constrained" strategy using Co4 molecular clusters and Fe(acac)3 implanted carbon precursors. The as-developed Co4 @/Fe1 @NC catalyst exhibits excellent ORR activity with a half-wave potential (E1/2 ) of 0.835 V vs. RHE in acidic media and a high peak power density of 840 mW cm-2 in a H2 -O2 fuel cell test. First-principles calculations further clarify the ORR catalytic mechanism on the identified Fe-N4 that modified with Co4 ACs. This work provides a viable strategy for precisely establishing atomically dispersed polymetallic centers catalysts for efficient energy-related catalysis.

In situ formation of cocatalytic sites boosts single-atom catalysts for nitrogen oxide reduction.

Nitrogen oxide (NOx) pollution presents a severe threat to the environment and human health. Catalytic reduction of NOx with H2 using single-atom catalysts poses considerable potential in the remediation of air pollution; however, the unfavorable process of H2 dissociation limits its practical application. Herein, we report that the in situ formation of PtTi cocatalytic sites (which are stabilized by Pt-Ti bonds) over Pt1/TiO2 significantly increases NOx conversion by reducing the energy barrier of H2 activation. We demonstrate that two H atoms of H2 molecule are absorbed by adjacent Pt atoms in Pt-O and Pt-Ti, respectively, which can promote the cleave of H-H bonds. Besides, PtTi sites facilitate the adsorption of NO molecules and further lower the activation barrier of the whole de-NOx reaction. Extending the concept to Pt1/Nb2O5 and Pd1/TiO2 systems also sees enhanced catalytic activities, demonstrating that engineering the cocatalytic sites can be a general strategy for the design of high-efficiency catalysts that can benefit environmental sustainability.

Liquid Fluxional Ga Single Atom Catalysts for Efficient Electrochemical CO2 Reduction.

Precise design and tuning of the micro-atomic structure of single atom catalysts (SACs) can help efficiently adapt complex catalytic systems. Herein, we inventively found that when the active center of the main group element gallium (Ga) is downsized to the atomic level, whose characteristic has significant differences from conventional bulk and rigid Ga catalysts. The Ga SACs with a P, S atomic coordination environment display specific flow properties, showing CO products with FE of ≈92 % at -0.3 V vs. RHE in electrochemical CO2 reduction (CO2 RR). Theoretical simulations demonstrate that the adaptive dynamic transition of Ga optimizes the adsorption energy of the *COOH intermediate and renews the active sites in time, leading to excellent CO2 RR selectivity and stability. This liquid single atom catalysts system with dynamic interfaces lays the foundation for future exploration of synthesis and catalysis.

Regulating the FeN4 Moiety by Constructing Fe-Mo Dual-Metal Atom Sites for Efficient Electrochemical Oxygen Reduction.

An Fe-N-C catalyst with an FeN4 active moiety has gained ever-increasing attention for the oxygen reduction reaction (ORR); however, the catalytic performance is sluggish in acidic solutions and the regulation is still a challenge. Herein, Fe-Mo dual-metal sites were constructed to tune the ORR activity of a mononuclear Fe site embedded in porous nitrogen-doped carbon. The cracking of O-O bonds is much more facile on the Fe-Mo atomic pair site due to the preferred bridge-cis adsorption model of oxygen molecules. The downshift of the Fe d band center when an Mo atom is introduced to the FeNx configuration optimizes the absorption-desorption behavior of ORR intermediates in the FeMoN6 active moiety, thus boosting the catalytic performance. The construction of dual-metal atom sites to regulate the catalytically active moiety paves the way for boosting the electrocatalytic performance of other similar non-precious-metal catalysts.

Revealing the Origin of Low-Temperature Activity of Ni-Rh Nanostructures during CO Oxidation Reaction with Operando TEM.

In bimetallic heterostructured nanoparticles (NPs), the synergistic effect between their different metallic components leads to higher catalytic activity compared to the activity of the individual components. However, how the dynamic changes through which these NPs adopt catalytically active structures during a reaction and how the restructuring affects their activity are largely unknown. Here, using operando transmission electron microscopy, structural changes are studied in bimetallic Ni-Rh NPs, comprising of a Ni core whose surface is decorated with smaller Rh NPs, during a CO oxidation reaction. The direct atomic-scale imaging reveals that, under O2 -rich conditions, Ni core partially transforms into NiO, forming a (Ni+NiO)-Rh hollow nanocatalyst with high catalytic activity. Under O2 -poor conditions, Rh NPs alloy with the surface of the core to form a NiRh-alloy surface, and the NPs display significantly lower activity. The theoretical calculations indicate that NiO component that forms only under O2 -rich conditions enhances the activity by preventing the CO poisoning of the nanocatalysts. The results demonstrate that visualizing the structural changes during reactions is indispensable in identifying the origin of catalytic activity. These insights into the dynamic restructuring of NP catalysts under a reactive environment are critical for the rational design of high-performance nanocatalysts.

Boosting Electrochemical Styrene Transformation via Tandem Water Oxidation over a Single-Atom Cr1 /CoSe2 Catalyst.

Electrocatalytic oxidation of organics using water as the oxygen source is a prospective but challenging method to produce high-value-added chemicals; especially, the competitive oxygen evolution reaction (OER) limits its efficiency. Herein, a tandem catalysis strategy based on a single-atom catalyst with Cr atoms atomically dispersed at a CoSe2 support (Cr1 /CoSe2 ) is presented. Thereinto, Co and Cr sites are endowed with a specific function to activate water and styrene respectively, and the competition between the OER and styrene oxidation is turned into mutual benefits via cooperated active sites. Under a potential of 1.6 VAg/AgCl , excellent selectivity of 95% to benzaldehyde and a high conversion rate of styrene at 88% without any exogenous oxidizing reagent are achieved. Isotopic tracing, isotope-labeled in situ Raman spectra, and detailed theoretical calculation further reveal the tandem mechanism, showing that the transfer of *OOH intermediates from the Co to the Cr sites serves as a bridge to link the oxidation of water and styrene. This work develops a new strategy for the co-oxidation of multi-species based on tandem catalysis, providing novel insights for the design of single-atom catalysts.

Identification of the Stable Pt Single Sites in the Environment of Ions: From Mechanism to Design Principle.

For single-atom (SA)-based catalysis, it is urgent to understand the nature and dynamic evolution of SA active sites during the reactions. In this work, an example of Pt SA-Zn0.5 Cd0.5 S (Pt SA-ZCS) is found to display interesting phenomena when facing the Brownian collision of ions in aqueous photocatalysis. Via synchrotron radiation, surface techniques, microscopy, and theory calculations, the results show that two kinds of Pt sites exist: PtZn-sub -S3 (Pt substituting the Zn site) and Ptads -S2 (Pt adsorbing on the surface). In Na2 S, the S2- can coordinate with Pt atoms and peel them from the Ptads -S2 sites, but leaves more stable PtZn-sub -S3 sites, bringing a low but stable catalytic activity (19.40 mmol g-1 h-1 ). Meanwhile, in ascorbic acid, the ascorbic acid ions show less complex ability with Pt atoms, but can decrease the migration barrier of Ptads -S2 sites (67.18 down to 35.96 mmol g-1 h-1 , 52.03% drop after 6 h). Therefore, the Ptads -S2 sites gradually aggregate into nanoclusters, bringing a high but decayed catalytic activity. Moreover, a Pt SA-ZCS-Sulfur composite is designed mainly covered by PtZn-sub -S3 sites accordingly (max: 79.09 mmol g-1 h-1 , 5% drop after 6 h and QE: 14.0% at 420 nm), showing a beneficial strategy "from mechanism to design principle."

Construction of Pd-Zn dual sites to enhance the performance for ethanol electro-oxidation reaction.

Rational design and synthesis of superior electrocatalysts for ethanol oxidation is crucial to practical applications of direct ethanol fuel cells. Here, we report that the construction of Pd-Zn dual sites with well exposure and uniformity can significantly improve the efficiency of ethanol electro-oxidation. Through synthetic method control, Pd-Zn dual sites on intermetallic PdZn nanoparticles, Pd-Pd sites on Pd nanoparticles and individual Pd sites are respectively obtained on the same N-doped carbon coated ZnO support. Compared with Pd-Pd sites and individual Pd sites, Pd-Zn dual sites display much higher activity for ethanol electro-oxidation, exceeding that of commercial Pd/C by a factor of ~24. Further computational studies disclose that Pd-Zn dual sites promote the adsorption of ethanol and hydroxide ion to optimize the electro-oxidation pathway with dramatically reduced energy barriers, leading to the superior activity. This work provides valuable clues for developing high-performance ethanol electro-oxidation catalysts for fuel cells.

Conjugated π Electrons of MOFs Drive Charge Separation at Heterostructures Interface for Enhanced Photoelectrochemical Water Oxidation.

Photoanode material with high efficiency and stability is extensively desirable in photoelectrochemical (PEC) water splitting for green/renewable energy source. Herein, novel heterostructures is constructed via coating rutile TiO2 nanorods with metal organic framework (MOF) materials UiO-66 or UiO-67 (UiO-66@TiO2 and UiO-67@TiO2 ), respectively. The π electrons in the MOF linkers could increase the local electronegativity near the heterojunction interface due to the conjugation effect, thereby enhancing the internal electric field (IEF) at the heterojunction interface. The IEF could drive charge transfer following Z-scheme mechanism in the prepared heterostructures, inducing photogenerated charge separation efficiency increasing as 156% and 253% for the UiO-66@TiO2 and UiO-67@TiO2 , respectively. Correspondingly, the UiO-66@TiO2 and UiO-67@TiO2 enhanced the photocurrent density as approximate two- and threefolds compared with that of pristine TiO2 for PEC water oxidation in universal pH electrolytes. This work demonstrates an effective method of regulating the IEF of heterojunction toward further improved charge separation.

Nitrene-functionalized ruthenium nanoparticles: Spectral evidence for the conjugated ruthenium-nitrene π bonds and the impact on the catalytic activity.

In this manuscript, ruthenium (Ru) nanoparticles functionalized with nitrene ligands through the ruthenium-nitrene (RuN) π bonds are explored. By synthesizing the nitrene ligands with and without 15N-labelling, RuN π bonds on Ru nanoparticles are evidenced by experimental and theoretically calculated FTIR spectra. The coordination of nitrene ligands on Ru nanoparticles surface, the interfacial charge delocalization and the impact of nitrene ligands on the catalytic performance of Ru nanoparticles are further characterized by magic-angle spinning solid-state carbon nuclear magnetic resonance spectroscopy (13C NMR) of 13CO-adsorbed Ru nanoparticles, photoluminescence and the hydrogenation of styrene.

Gram-Scale Synthesis of High-Loading Single-Atomic-Site Fe Catalysts for Effective Epoxidation of Styrene.

Single-atomic-site (SAS) catalysts, a new frontier of catalysts, always show extremely high atom efficiency and unexpected catalytic properties. Herein, a pyrolyzing coordinated polymer (PCP) strategy is developed, which is facile and widely applicable in the synthesis of a series of SAS catalysts including SAS-Fe, SAS-Ni, SAS-Cu, SAS-Zn, SAS-Ru, SAS-Rh, SAS-Pd, SAS-Pt, and SAS-Ir. The as-obtained SAS catalysts can be easily synthesized at gram scale and the metal loading of SAS-Fe catalysts achieves a record value of 30 wt%, which meets the requirement of practical applications. Moreover, it is discovered that SAS-Fe catalysts show unprecedented catalytic performance for epoxidation of styrene using O2 as the only oxidant (yield: 64%; selectivity: 89%), while Fe nanoparticles and ironporphyrin are inactive. This discovery is believed to pave the way for exploiting the unparalleled properties of SAS catalysts and promoting their industrial applications.

Engineering Isolated Mn-N2C2 Atomic Interface Sites for Efficient Bifunctional Oxygen Reduction and Evolution Reaction.

Oxygen-involved electrochemical reactions are crucial for plenty of energy conversion techniques. Herein, we rationally designed a carbon-based Mn-N2C2 bifunctional electrocatalyst. It exhibits a half-wave potential of 0.915 V versus reversible hydrogen electrode for oxygen reduction reaction (ORR), and the overpotential is 350 mV at 10 mA cm-2 during oxygen evolution reaction (OER) in alkaline condition. Furthermore, by means of operando X-ray absorption fine structure measurements, we reveal that the bond-length-extended Mn2+-N2C2 atomic interface sites act as active centers during the ORR process, while the bond-length-shortened high-valence Mn4+-N2C2 moieties serve as the catalytic sites for OER, which is consistent with the density functional theory results. The atomic and electronic synergistic effects for the isolated Mn sites and the carbon support play a critical role to promote the oxygen-involved catalytic performance, by regulating the reaction free energy of intermediate adsorption. Our results give an atomic interface strategy for nonprecious bifunctional single-atom electrocatalysts.

Efficient Electrochemical Nitrogen Fixation over Isolated Pt Sites.

Recently, ambient electrochemical N2 fixation has gained great attention. However, the commercial Pt-based electrocatalyst hardly shows its potential in this field. Herein, it is found that the isolated Pt sites anchored on WO3 nanoplates exhibit the optimum electrochemical NH3 yield rate (342.4 µg h-1 mg-1 Pt ) and Faradaic efficiency (31.1%) in 0.1 m K2 SO4 at -0.2 V versus RHE, which are about 11 and 15 times higher than their nanoparticle counterparts, respectively. The mechanistic analysis indicates that N2 conversion to NH3 follows an alternating hydrogenation pathway, and positively charged isolated Pt sites with special Pt-3O structure can favorably chemisorb and activate the N2 . Furthermore, the hydrogen evolution reaction can be greatly suppressed on isolated Pt sites decorated WO3 nanoplates, which guarantees the efficient going-on of nitrogen reduction reaction.

Controlled Synthesis of Ni-Doped MoS2 Hybrid Electrode for Synergistically Enhanced Water-Splitting Process.

The development of high-efficiency, low-cost, and earth-abundant electrocatalysts for overall water splitting remains a challenge. In this work, Ni-modified MoS2 hybrid catalysts are grown on carbon cloth (Ni-Mo-S@CC) through a one-step hydrothermal treatment. The optimized Ni-Mo-S@CC catalyst shows excellent hydrogen evolution reaction (HER) activity with a low overpotential of 168 mV at a current density of 10 mA cm-2 in 1.0 m KOH, which is lower than those of Ni-Mo-S@CC (1:1), Ni-Mo-S@CC (3:1), and pure MoS2 . Significantly, the Ni-Mo-S@CC hybrid catalyst also displays outstanding oxygen evolution reaction (OER) activity with a low overpotential of 320 mV at a current density of 10 mA cm-2 , and remarkable long-term stability for 30 h at a constant current density of 10 mA cm-2 . Experimental results and theoretical analysis based on density functional theory demonstrate that the excellent electrocatalytic performance can be attributed mainly to the remarkable conductivity, abundant active sites, and synergistic effect of the Ni-doped MoS2 . This work sheds light on a unique strategy for the design of high-performance and stable electrocatalysts for water-splitting electrolyzers.