Calcium Single Atom Confined in Nitrogen-Doped Carbon-Coupled Polyvinylidene Fluoride Membrane for High-Performance Piezocatalysis.

A piezoelectric polymer membrane based on single metal atoms was demonstrated to be effective by anchoring isolated calcium (Ca) atoms on a composite of nitrogen-doped carbon and polyvinylidene fluoride (PVDF). The addition of Ca-atom-anchored carbon nanoparticles not only promotes the formation of the ß phase (from 29.8 to 56.3%), the most piezoelectrically active phase, in PVDF, but also introduces much higher porosity and hydrophilicity. Under ultrasonic excitation, the fabricated catalyst membrane demonstrates a record-high and stable dye decomposing rate of 0.11 min-1 and antibacterial efficiencies of 99.8%. Density functional theory calculations reveal that the primary contribution to catalytic activity arises from single-atom Ca doping and that a possible synergistic effect between PVDF and Ca atoms can improve the catalytic performance. It is shown that O2 molecules can be easily hydrogenated to produce ·OH on Ca-PVDF, and the local electric field provided by the ß-phase-PVDF might enhance the production of ·O2-. The proposed polymer membrane is expected to inspire the rational design of piezocatalysts and pave the way for the application of piezocatalysis technology for practical environmental remediation.

Direct Observation of Z-Scheme Route in Cu31 S16 /Znx Cd1-x S Heteronanoplates for Highly Efficient Photocatalytic Hydrogen Evolution.

Although photocatalytic hydrogen production from water holds great potential as a renewable and sustainable energy alternative, the practical application of the technology demands cost-effective, simple photocatalytic systems with high efficiency in hydrogen evolution reaction (HER). Herein, the synthesis and characterization of Cu31 S16 /Znx Cd1-x S heterostructured nanoplates (Cu31 S16 /ZnCdS HNPs) as a high photocatalytic system are reported. The cost-effective, hierarchical structures are easily prepared using the Cu31 S16 NPs as the seed by the epitaxial growth of the ZnCdS nanocrystals (NCs). The Cu31 S16 /ZnCdS without the noble metal cocatalyst exhibits a high HER rate of 61.7 mmol g-1  h-1 , which is 8,014 and 17 times higher than that of Cu31 S16 and ZnCdS, respectively, under visible light irradiation. The apparent quantum yield (AQY) of Cu31 S16 /ZnCdS reaches 67.9% at 400 nm with the highest value so far in the reported ZnCdS-based photocatalysts. The excellent activity and stability of the Cu31 S16 /ZnCdS are attributed to the formation of a strong internal electric field (IEF) and the Z-scheme pathway. The comprehensive experiments and theoretical calculations provide the direct evidences of the Z-scheme route. This work may offer a way for the design and development of efficient photocatalysts to achieve solar-to-chemical energy conversion at a practically useful level.

Comprehensive suppression of single-molecule conductance using destructive σ-interference.

The tunnelling of electrons through molecules (and through any nanoscale insulating and dielectric material 1 ) shows exponential attenuation with increasing length 2 , a length dependence that is reflected in the ability of the electrons to carry an electrical current. It was recently demonstrated3-5 that coherent tunnelling through a molecular junction can also be suppressed by destructive quantum interference 6 , a mechanism that is not length-dependent. For the carbon-based molecules studied previously, cancelling all transmission channels would involve the suppression of contributions to the current from both the π-orbital and σ-orbital systems. Previous reports of destructive interference have demonstrated a decrease in transmission only through the π-channel. Here we report a saturated silicon-based molecule with a functionalized bicyclo[2.2.2]octasilane moiety that exhibits destructive quantum interference in its σ-system. Although molecular silicon typically forms conducting wires 7 , we use a combination of conductance measurements and ab initio calculations to show that destructive σ-interference, achieved here by locking the silicon-silicon bonds into eclipsed conformations within a bicyclic molecular framework, can yield extremely insulating molecules less than a nanometre in length. Our molecules also exhibit an unusually high thermopower (0.97 millivolts per kelvin), which is a further experimental signature of the suppression of all tunnelling paths by destructive interference: calculations indicate that the central bicyclo[2.2.2]octasilane unit is rendered less conductive than the empty space it occupies. The molecular design presented here provides a proof-of-concept for a quantum-interference-based approach to single-molecule insulators.

Tailored Exfoliation of Polymeric Carbon Nitride for Photocatalytic H2O2 Production and CH4 Valorization Mediated by O2 Activation.

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.

Photo-self-Fenton Reaction Mediated by Atomically Dispersed Ag-Co Photocatalysts toward Efficient Degradation of Organic Pollutants.

Achieving the complete mineralization of persistent pollutants in wastewater is still a big challenge. Here, we propose an efficient photo-self-Fenton reaction for the degradation of different pollutants using the high-density (Ag: 22 wt %) of atomically dispersed AgCo dual sites embedded in graphic carbon nitride (AgCo-CN). Comprehensive experimental measurements and density functional theory (DFT) calculations demonstrate that the Ag and Co dual sites in AgCo-CN play a critical role in accelerating the photoinduced charge separation and forming the self-Fenton redox centers, respectively. The bimetallic AgCo-CN exhibited excellent photocatalytic performance toward the phenol even under extreme conditions due to an efficient degradation pathway and in situ generation of the hydrogen peroxide producing the main active oxygen species (⋅OH and 1 O2 ) and showed long-term activity in a self-design photo-Filter reactor for the purification of the phenol. Our discoveries pave the way for the design of efficient single-atoms photocatalysts-based photo-self-Fenton reaction for recalcitrant pollutant treatment.

Infrared Light-Induced Anomalous Defect-Mediated Plasmonic Hot Electron Transfer for Enhanced Photocatalytic Hydrogen Evolution.

Efficient utilization of infrared (IR) light, which occupies almost half of the solar energy, is an important but challenging task in solar-to-fuel transformation. Herein, we report the discovery of CuS@ZnS core@shell nanocrystals (CSNCs) with strong localized surface plasmon resonance (LSPR) characteristics in the IR light region showing enhanced photocatalytic activity in hydrogen evolution reaction (HER). A unique "plasmon-induced defect-mediated carrier transfer" (PIDCT) at the heterointerfaces of the CSNCs divulged by time-resolved transient spectroscopy enables producing a high quantum yield of 29.2%. The CuS@ZnS CSNCs exhibit high activity and stability in H2 evolution under near-IR light irradiation. The HER rate of CuS@ZnS CSNCs at 26.9 µmol h-1 g-1 is significantly higher than those of CuS NCs (0.4 µmol h-1 g-1) and CuS/ZnS core/satellite heterostructured NCs (15.6 µmol h-1 g-1). The PIDCT may provide a viable strategy for the tuning of LSPR-generated carrier kinetics through controlling the defect engineering to improve photocatalytic performance.

Noble-Metal-Metalloid Alloy Architectures: Mesoporous Amorphous Iridium-Tellurium Alloy for Electrochemical N2 Reduction.

Amorphous noble metals with high surface areas have attracted significant interest as heterogeneous catalysts due to the numerous dangling bonds and abundant unsaturated surface atoms created by the amorphous phase. However, synthesizing amorphous noble metals with high surface areas remains a significant challenge due to strong isotropic metallic bonds. This paper describes the first example of a mesoporous amorphous noble metal alloy [iridium-tellurium (IrTe)] obtained using a micelle-directed synthesis method. The resulting mesoporous amorphous IrTe electrocatalyst exhibits excellent performance in the electrochemical N2 reduction reaction. The ammonia yield rate is 34.6 µg mg-1 h-1 with a Faradaic efficiency of 11.2% at -0.15 V versus reversible hydrogen electrode in 0.1 M HCl solution, outperforming comparable crystalline and Ir metal counterparts. The interconnected porous scaffold and amorphous nature of the alloy create a complementary effect that simultaneously enhances N2 absorption and suppresses the hydrogen evolution reaction. According to theoretical simulations, incorporating Te in the IrTe alloy effectively strengthens the adsorption of N2 and lowers the Gibbs free energy for the rate-limiting step of the electrocatalytic N2 reduction reaction. Mesoporous chemistry enables a new route to achieve high-performance amorphous metalloid alloys with properties that facilitate the selective electrocatalytic reduction of N2.

Fe2O3/TiO2/reduced graphene oxide-driven recycled visible-photocatalytic Fenton reactions to mineralize organic pollutants in a wide pH range.

Photocatalytic Fenton reactions combined the advantages from both photocatalysis and Fenton reaction in mineralizing organic pollutants. The key problems are the efficiency and recycling stability. Herein, we reported a novel Fe2O3/TiO2/reduced graphene oxide (FTG) nanocomposite synthesized by a facile solvothermal method. The TiO2 in FTG degraded organic pollutants and mineralized intermediates via photocatalysis under visible light irradiation, which could also promote Fenton reaction by accelerating Fe3+-Fe2+ recycle. Meanwhile, the Fe2O3 rapidly degraded organic pollutants via Fenton reactions, which also promoted photocatalysis by enhancing visible light absorbance and diminishing photoelectron-hole recombination. The high distribution of TiO2 and Fe2O3 on rGO, together with their strong interaction resulted in enhanced synergetic cooperation between photocatalysis and Fenton reactions, leading to the high mineralization efficiency of organic pollutants. More importantly, it could also inhibit the leaching of Fe species, leading to the long lifetime of FTG during photocatalytic Fenton reactions in a wide pH range from 3.4 to 9.2.

Correlating Oxidation State and Surface Ligand Motifs with the Selectivity of CO2 Photoreduction to C2 Products.

The design for non-Cu-based catalysts with the function of producing C2+ products requires systematic knowledge of the intrinsic connection between the surface state as well as the catalytic activity and selectivity. In this work, photochemical in situ spectral surface characterization techniques combined with the first principle calculations (DFT) were applied to investigate the relationships between the composition of surface states, coordinated motifs, and catalytic selectivity of a titanium oxynitride catalyst. When the catalyst mediates CO2 photoreduction, C2 product selectivity is positively correlated with the surface Ti2+ /Ti3+ ratio and the surface oxidation state is regulated and controlled by coordinated motifs of N-Ti-O/V[O], which can reduce the potential dimerization energy barriers of *CO-CO* and promote spontaneous formation of the subsequent *CO-CH2 * intermediate. This phenomenon provides a new perspective for the design of heterogeneous catalysts for photoreduction of CO2 into useful products.

Tailoring the Asymmetric Structure of NH2 -UiO-66 Metal-Organic Frameworks for Light-promoted Selective and Efficient Gold Extraction and Separation.

Designing adsorption materials with high adsorption capacities and selectivities is highly desirable for precious metal recovery. Desorption performance is also particularly crucial for subsequent precious metal recovery and adsorbent regeneration. Herein, a metal-organic framework (MOF) material (NH2 -UiO-66) with an asymmetric electronic structure of the central zirconium oxygen cluster has an exceptional gold extraction capacity of 2.04 g g-1 under light irradiation. The selectivity of NH2 -UiO-66 for gold ions is up to 98.8 % in the presence of interfering ions. Interestingly, the gold ions adsorbed on the surface of NH2 -UiO-66 spontaneously reduce in situ, undergo nucleation and growth and finally achieve the phase separation of high-purity gold particles from NH2 -UiO-66. The desorption and separation efficiency of gold particles from the adsorbent surface reaches 89 %. Theoretical calculations indicate that -NH2 functions as a dual donor of electrons and protons, and the asymmetric structure of NH2 -UiO-66 leads to energetically advantageous multinuclear gold capture and desorption. This adsorption material can greatly facilitate the recovery of gold from wastewater and can easily realize the recycling of the adsorbent.

Photocatalytic Free Radical-Controlled Synthesis of High-Performance Single-Atom Catalysts.

Single-atom catalysts (SACs) have emerged as crucial players in catalysis research, prompting extensive investigation and application. The precise control of metal atom nucleation and growth has garnered significant attention. In this study, we present a straightforward approach for preparing SACs utilizing a photocatalytic radical control strategy. Notably, we demonstrate for the first time that radicals generated during the photochemical process effectively hinder the aggregation of individual atoms. By leveraging the cooperative anchoring of nitrogen atoms and crystal lattice oxygen on the support, we successfully stabilize the single atom. Our Pd1 /TiO2 catalysts exhibit remarkable catalytic activity and stability in the Suzuki-Miyaura cross-coupling reaction, which was 43 times higher than Pd/C. Furthermore, we successfully depose Pd atoms onto various substrates, including TiO2 , CeO2 , and WO3 . The photocatalytic radical control strategy can be extended to other single-atom catalysts, such as Ir, Pt, Rh, and Ru, underscoring its broad applicability.

Hydroxyl Radical-Mediated Efficient Photoelectrocatalytic NO Oxidation with Simultaneous Nitrate Storage Using A Flow Photoanode Reactor.

The selective conversion of dilute NO pollutant into low-toxic product and simultaneous storage of metabolic nitrogen for crop plants remains a great challenge from the perspective of waste management and sustainable chemistry. This study demonstrates that this bottleneck can be well tackled by refining the reactive oxygen species (ROS) on Ni-modified NH2 -UiO-66(Zr) (Ni@NU) using nickel foam (NF) as a three-dimensional (3D) substrate through a flow photoanode reactor via the gas-phase photoelectrocatalysis. By rationally refining the ROS to ⋅OH, Ni@NU/NF can rapidly eliminate 82 % of NO without releasing remarkable NO2 under a low bias voltage (0.3 V) and visible light irradiation. The abundant mesoporous pores on Ni@NU/NF are conducive to the diffusion and storage of the formed nitrate, which enables the progressive conversion NO into nitrate with selectivity over 99 % for long-term use. Through calculation, 90 % of NO could be recovered as the nitrate species, indicating that this state-of-the-art strategy can capture, enrich and recycle the pollutant N source from the atmosphere. This study offers a new perspective of NO pollutant treatment and sustainable nitrogen exploitation, which may possess great potential to the development of highly efficient air purification systems for industrial and indoor NOx control.

Soft Template-Based Synthesis of Mesoporous Phosphorus- and Boron-Codoped NiFe-Based Alloys for Efficient Oxygen Evolution Reaction.

Controlling the morphology, composition, and crystalline phase of mesoporous nonnoble metal catalysts is essential for improving their performance. Herein, well-defined P- and B-codoped NiFe alloy mesoporous nanospheres (NiFeB-P MNs) with an adjustable Ni/Fe ratio and large mesopores (11 nm) are synthesized via soft-template-based chemical reduction and a subsequent phosphine-vapor-based phosphidation process. Earth-abundant NiFe-based materials are considered promising electrocatalysts for the oxygen evolution reaction (OER) because of their low cost and high intrinsic catalytic activity. The resulting NiFeB-P MNs exhibit a low OER overpotential of 252 mV at 10 mA cm-2 , which is significantly smaller than that of B-doped NiFe MNs (274 mV) and commercial RuO2 (269 mV) in alkaline electrolytes. Thus, this work highlights the practicality of designing mesoporous nonnoble metal structures and the importance of incorporating P in metallic-B-based alloys to modify their electronic structure for enhancing their intrinsic activity.

Singlet Oxygen and Mobile Hydroxyl Radicals Co-operating on Gas-Solid Catalytic Reaction Interfaces for Deeply Oxidizing NOx.

Learning from the important role of porphyrin-based chromophores in natural photosynthesis, a bionic photocatalytic system based on tetrakis (4-carboxyphenyl) porphyrin-coupled TiO2 was designed for photo-induced treating low-concentration NOx indoor gas (550 parts per billion), achieving a high NO removal rate of 91% and a long stability under visible-light (λ ≥ 420 nm) irradiation. Besides the great contribution of the conventional •O2- reactive species, a synergic effect between a singlet oxygen (1O2) and mobile hydroxyl radicals (•OHf) was first illustrated for removing NOx indoor gas (1O2 + 2NO → 2NO2, NO2 + •OHf → HNO3), inhibiting the production of the byproducts of NO2. This work is helpful for understanding the surface mechanism of photocatalytic NOx oxidation and provides a new perspective for the development of highly efficient air purification systems.

Power Management and Reaction Optimization for a Self-Powered Electrochemical System Driven by a Triboelectric Nanogenerator.

Harvesting distributed and low-quality mechanical energies by triboelectric nanogenerators to power electrochemical reactions is beneficial to electric energy saving and certain applications. However, the conventional self-powered electrochemical process is awkward about the reaction rate, energy conversion efficiency, high-operation frequency, and mismatched impedance. Here we demonstrate an advanced self-powered electrochemical system. In comparison with the conventional system that is inert in activity, the superior power management and electrochemical reaction regulation in tandem make the novel system outstanding for hydrogen peroxide production. In addition to the visible product, an internal current efficiency of 24.6% in the system was achieved. The developed system provides an optimization strategy toward electric energy saving for electrochemical reactions as well as enabling their applications in remote areas by converting environmental mechanical vibrational energy for ecological improvement or recyclable chemical fuel generation.

Photocatalytic Dissolution of Precious Metals by TiO2 through Photogenerated Free Radicals.

Exploring the pathways for photocatalytic dissolution of precious metals (PMs) is crucial for optimizing recovery. In this work, we systematically investigated the selectivity and solvation effects observed for dissolution by focusing on photocatalysis, precious metals and solvents. By combining transient characterization, reaction kinetics, and density functional theory, we determined that the radicals generated in photocatalysis were the key active species in the entire reaction. The cyano functional group in the solvent was the driving factor for dissolution of gold, and the importance of chlorine radicals for dissolution of platinum group precious metals was further confirmed. In addition, the catalytic properties of different precious metals can promote different transformations of functional groups, leading to selective dissolution. The structures of photocatalytic precious metal leaches also precisely explains the special coordination forms of precious metals and functional group ligands.

Cumulene Wires Display Increasing Conductance with Increasing Length.

One-dimensional sp-hybridized carbon wires, including cumulenes and polyynes, can be regarded as finite versions of carbynes. They are likely to be good candidates for molecular-scale conducting wires as they are predicted to have a high-conductance. In this study, we first characterize the single-molecule conductance of a series of cumulenes and polyynes with a backbone ranging in length from 4 to 8 carbon atoms, including [7]cumulene, the longest cumulenic carbon wire studied to date for molecular electronics. We observe different length dependence of conductance when comparing these two forms of carbon wires. Polyynes exhibit conductance decays with increasing molecular length, while cumulenes show a conductance increase with increasing molecular length. Their distinct conducting behaviors are attributed to their different bond length alternation, which is supported by theoretical calculations. This study confirms the long-standing theoretical predictions on sp-hybridized carbon wires and demonstrates that cumulenes can form highly conducting molecular wires.

Mesoporous Metal-Metalloid Amorphous Alloys: The First Synthesis of Open 3D Mesoporous Ni-B Amorphous Alloy Spheres via a Dual Chemical Reduction Method.

Selective hydrogenation of nitriles is an industrially relevant synthetic route for the preparation of primary amines. Amorphous metal-boron alloys have a tunable, glass-like structure that generates a high concentration of unsaturated metal surface atoms that serve as active sites in hydrogenation reactions. Here, a method to create nanoparticles composed of mesoporous 3D networks of amorphous nickel-boron (Ni-B) alloy is reported. The hydrogenation of benzyl cyanide to ß-phenylethylamine is used as a model reaction to assess catalytic performance. The mesoporous Ni-B alloy spheres have a turnover frequency value of 11.6 h-1 , which outperforms non-porous Ni-B spheres with the same composition. The bottom-up synthesis of mesoporous transition metal-metalloid alloys expands the possible reactions that these metal architectures can perform while simultaneously incorporating more Earth-abundant catalysts.

Gas-Phase Photoelectrocatalytic Oxidation of NO via TiO2 Nanorod Array/FTO Photoanodes.

Most photoelectrocatalytic (PEC) reactions are performed in the liquid phase for convenient electron transfer in an electrolyte solution. Herein, a novel PEC reactor involving a tandem combination of TiO2 nanorod array/fluorine-doped tin oxide (TiO2-NR/FTO) working electrodes and an electrochemical auxiliary cell was constructed to drive the highly efficient PEC oxidation of indoor gas (NOx). With the aid of a low bias voltage (0.3 V), the as-formed PEC reactor exhibited an 80% removal rate for oxidizing NO (500 ppb) under light irradiation, which is much higher than that of the traditional photocatalytic (PC) process. Upon being irradiated by light, the photogenerated electrons are quickly separated from the holes and transferred to the counter electrode (Pt) owing to the applied bias voltage, leaving photogenerated holes in the TiO2-NR/FTO electrode for oxidizing NO molecules. Moreover, both dry and humid NO could be effectively removed by the tandem TiO2-NR/FTO-based gas-phase PEC reactor, indicating that the NO molecules could also be directly oxidized by photogenerated holes in addition to hydroxyl radicals. The presence of trace amounts of water could promote the PEC oxidation of NO owing to the formation of hydroxyl radicals induced by reactions between the water and holes, which could further oxidize NO. This PEC reactor offers an energy-saving, environmentally friendly, and efficient route to treat air polluted with low concentrations of gases (NOx and SOx).

Stringing the Perylene Diimide Bow.

This study explores a new mode of contortion in perylene diimides where the molecule is bent, like a bow, along its long axis. These bowed PDIs were synthesized through a facile fourfold Suzuki macrocyclization with aromatic linkers and a tetraborylated perylene diimide that introduces strain and results in a bowed structure. By altering the strings of the bow, the degree of bending can be controlled from flat to highly bent. Through spectroscopy and quantum chemical calculations, it is demonstrated that the energy of the lowest unoccupied orbital can be controlled by the degree of bending in the structures and that the energy of the highest occupied orbital can be controlled to a large extent by the constitution of the aromatic linkers. The important finding is that the bowing results not only in red-shifted absorptions but also more facile reductions.