Sub-10-nm-sized Au@AuxIr1-x metal-core/alloy-shell nanoparticles as highly durable catalysts for acidic water splitting.

The absence of efficient and durable catalysts for oxygen evolution reaction (OER) is the main obstacle to hydrogen production through water splitting in an acidic electrolyte. Here, we report a controllable synthesis method of surface IrOx with changing Au/Ir compositions by constructing a range of sub-10-nm-sized core-shell nanocatalysts composed of an Au core and AuxIr1-x alloy shell. In particular, Au@Au0.43Ir0.57 exhibits 4.5 times higher intrinsic OER activity than that of the commercial Ir/C. Synchrotron X-ray-based spectroscopies, electron microscopy and density functional theory calculations revealed a balanced binding of reaction intermediates with enhanced activity. The water-splitting cell using a load of 0.02 mgIr/cm2 of Au@Au0.43Ir0.57 as both anode and cathode can reach 10 mA/cm2 at 1.52 V and maintain activity for at least 194 h, which is better than the cell using the commercial couple Ir/C‖Pt/C (1.63 V, 0.2 h).

Monolayer NiIr-Layered Double Hydroxide as a Long-Lived Efficient Oxygen Evolution Catalyst for Seawater Splitting.

Promoting the oxygen evolution reaction (OER) with saline water is highly desired to realize seawater splitting. This requires OER catalysts to resist serious corrosion and undesirable chloride oxidation. We introduce a 5d transition metal, Ir, to develop a monolayer NiIr-layered double hydroxide (NiIr-LDH) as the catalyst with enhanced OER performance for seawater splitting. The NiIr-LDH catalyst delivers 500 mA/cm2 at only 361 mV overpotential with ∼99% O2 Faradaic efficiency in alkaline seawater, which is more active than commercial IrO2 (763 mV, 23%) and the best known OER catalyst NiFe-LDH (530 mV, 92%). Moreover, it shows negligible activity loss at up to 650 h chronopotentiometry measurements at an industrial level (500 mA/cm2), while commercial IrO2 and NiFe-LDH rapidly deactivated within 0.2 and 10 h, respectively. The incorporation of Ir into the Ni(OH)2 layer greatly altered the electron density of Ir and Ni sites, which was revealed by X-ray absorption fine structure and density functional theory (DFT) calculations. Coupling the electrochemical measurements and in situ Raman spectrum with DFT calculations, we further confirm that the generation of rate-limiting intermediate *O and *OOH species was accelerated on Ni and Ir sites, respectively, which is responsible for the high seawater splitting performance. Our results also provide an opportunity to fabricate LDH materials containing 5d metals for applications beyond seawater splitting.

Significantly Enhanced Overall Water Splitting Performance by Partial Oxidation of Ir through Au Modification in Core-Shell Alloy Structure.

Developing efficient bifunctional electrocatalysts for overall water splitting in acidic conditions is the essential step for proton exchange membrane water electrolyzers (PEMWEs). We first report the synthesis of core-shell structure nanoparticles (NPs) with an Au core and an AuIr2 alloy shell (Au@AuIr2). Au@AuIr2 displayed 4.6 (5.6) times higher intrinsic (mass) activity toward the oxygen evolution reaction (OER) than a commercial Ir catalyst. Furthermore, it showed hydrogen evolution reaction (HER) catalytic properties comparable to those of commercial Pt/C. Significantly, when Au@AuIr2 was used as both the anode and cathode catalyst, the overall water splitting cell achieved 10 mA/cm2 with a low cell voltage of 1.55 V and maintained this activity for more than 40 h, which greatly outperformed the commercial couples (Ir/C||Pt/C, 1.63 V, activity decreased within minutes) and is among the most efficient bifunctional catalysts reported. Theoretical calculations coupled with X-ray-based structural analyses suggest that partially oxidized surfaces originating from the electronic interaction between Au and Ir provide a balance for different intermediates binding and realize significantly enhanced OER performance.

Enhanced selectivity and stability towards CO2 reduction of sub-5 nm Au NPs derived from supramolecular assembly.

We report three well-defined types of Au nanoparticles (NPs) protected by rigid macrocyclic cucurbit[n]uril (CB[n]) (CB[n]-Au), which are prepared via the supramolecular self-assembly of the precursors. CB[n]-Au shows excellent catalytic activity and selectivity, with a performance that can be maintained for up to 72 h in the electroreduction of CO2 to CO. The effects of the structural features of different CB[n]s on the electrocatalytic performance of the Au NPs have been revealed for the first time.

Hollow Mesoporous Carbon Sphere Loaded Ni-N4 Single-Atom: Support Structure Study for CO2 Electrocatalytic Reduction Catalyst.

Single-atom catalysts have become a hot spot because of the high atom utilization efficiency and excellent activity. However, the effect of the support structure in the single-atom catalyst is often unnoticed in the catalytic process. Herein, a series of carbon spheres supported Ni-N4 single-atom catalysts with different support structures are successfully synthesized by the fine adjustment of synthetic conditions. The hollow mesoporous carbon spheres supported Ni-N4 catalyst (Ni/HMCS-3-800) exhibits superior catalytic activity toward the electrocatalytic CO2 reduction reaction (CO2 RR). The Faradaic efficiency toward CO is high to 95% at the potential range from -0.7 to -1.1 V versus reversible hydrogen electrode and the turnover frequency value is high up to 15 608 h-1 . More importantly, the effect of the geometrical structures of carbon support on the CO2 RR performance is studied intensively. The shell thickness and compactness of carbon spheres regulate the chemical environment of the doped-N species in the carbon skeleton effectively and promote CO2 molecule activation. Additionally, the optimized mesopore size is beneficial to improve diffusion and overflow of the substance, which enhances the CO2 adsorption capacity greatly. This work provides a new consideration for promoting the catalytic performance of single-atom catalysts.

Ultrafine Ru nanoclusters anchored on cucurbit[6]uril/rGO for efficient hydrogen evolution in a broad pH range.

We report for the first time ultrafine Ru nanoclusters (NCs) anchored on thin reduced graphene oxide (rGO) via introduction of the macrocyclic compound cucurbit[6]uril (CB[6]). The nanocomposite exhibits a comparable or better HER performance compared to Pt/C in acidic, alkaline as well as neutral media, which greatly broadens its application in different types of electrolyzers.

Encapsulating metal organic framework into hollow mesoporous carbon sphere as efficient oxygen bifunctional electrocatalyst.

Applying metal organic frameworks (MOFs) in electrochemical systems is a currently emerging field owing to the rich metal nodes and highly specific surface area of MOFs. However, the problems for MOFs that need to be solved urgently are poor electrical conductivity and low ion transport. Here we present a facile in situ growth method for the rational synthesis of MOFs@hollow mesoporous carbon spheres (HMCS) yolk-shell-structured hybrid material for the first time. The size of the encapsulated Zeolitic Imidazolate Framework-67 (ZIF-67) is well controlled to 100 nm due to the spatial confinement effect of HMCS, and the electrical conductivity of ZIF-67 is also increased significantly. The ZIF@HMCS-25% hybrid material obtained exhibits a highly efficient oxygen reduction reaction activity with 0.823 V (vs. reversible hydrogen electrode) half-wave potential and an even higher kinetic current density (J K = 13.8 mA cm-2) than commercial Pt/C. ZIF@HMCS-25% also displays excellent oxygen evolution reaction performance and the overpotential of ZIF@HMCS-25% at 10 mA cm-2 is 407 mV. In addition, ZIF@HMCS-25% is further employed as an air electrode for a rechargeable Zn-air battery, exhibiting a high power density (120.2 mW cm-2 at 171.4 mA cm-2) and long-term charge/discharge stability (80 h at 5 mA cm-2). This MOFs@HMCS yolk-shell design provides a versatile method for the application of MOFs as electrocatalysts directly.

N-Doped holey carbon materials derived from a metal-free macrocycle cucurbit[6]uril assembly as an efficient electrocatalyst for the oxygen reduction reaction.

The first example of the preparation of nitrogen-doped holey carbon (NHC) with abundant in-plane holes derived from a rigid macrocycle cucurbit[6]uril self-assembly is reported. The NHC shows comparable activity, better stability and higher methanol tolerance towards the oxygen reduction reaction compared to the use of commercial Pt/C.

Decamethylcucurbit[5]uril based supramolecular assemblies as efficient electrocatalysts for the oxygen reduction reaction.

A series of supramolecular assemblies were constructed using decamethylcucurbit[5]uril. Coordination of an alkali metal and further linkage by [PtCl6]2- created a 1D building block, which formed a 3D structure through abundant hydrogen bonds. The obtained supramolecular assemblies exhibited excellent electrocatalytic performance towards the oxygen reduction reaction, comparable to the commercial Pt/C catalyst. Full characterizations, as well as density functional theory calculation results, demonstrated the structure-performance relationship.

Ultra-small Pd nanoparticles derived from a supramolecular assembly for enhanced electrochemical reduction of CO2 to CO.

Ultra-small Pd nanoparticles were successfully prepared through reduction of a supramolecular assembly formed between the macrocyclic decamethylcucurbit[5]uril (Me10CB[5]) and [PdCl4]2- anions via H-bonds. The final Pd NPs exhibit excellent activity and stability toward the electrochemical reduction of CO2 to CO. This work provides a new strategy for the preparation of nanocatalysts.

Hemangioma treatment with pulsed dye laser-distinct parameters used between neonatal and non-neonatal patients.

BACKGROUND: Pulsed dye laser (PDL) treatment remains the standard of care for infantile hemangiomas (IHs). However, the use of PDL to treat IHs in neonates has been hardly reported. In this study, the PDL treatments of IHs between neonatal and non-neonatal patients were retrospectively investigated. METHODS: All patients diagnosed with hemangiomas were treated by PDL. Their clinical data were collected, and the treatment outcomes and PDL parameters in neonates and non-neonates were analyzed using the Mann-Whitney U-rank test. RESULTS: All patients reached good or excellent scale in the treatment efficiency assessment. Laser energy used per treatment session was significantly lower in neonatal group than in non-neonatal group (Z = -8.980, P < 0.001). Total laser energy used in neonates was also markedly lower than that in non-neonatal patients (Z = -3.065, P = 0.002). However, treatment session numbers in these two groups were not significantly different (Z = -1.725, P = 0.085). Additionally, we observed that after each treatment, the purpura disappeared faster in neonates (2-4 weeks) than in non-neonatal patients (4-6 weeks), indicating neonates might have greater recovery ability. CONCLUSIONS: PDL, with distinct parameters, was effective in the treatment of IHs in neonates. After each laser treatment, neonates recovered faster than non-neonatal patients.

Ru-assisted synthesis of {111}-faceted Pd truncated bipyramids: a highly reactive, stable and restorable catalyst for formic acid oxidation.

{111}-Faceted Pd truncated triangular bipyramids (TTBPs) are first presented under the assistance of Ru. Attributed to their unique shape, the TTBPs are highly active and stable for formic acid oxidation. The electrochemical active surface area (ECSA) can be restored to its initial value after a harsh degradation test.

Crystalline hybrid solid materials of palladium and decamethylcucurbit[5]uril as recoverable precatalysts for Heck cross-coupling reactions.

A series of MPdMe10 CB[5] (M=Li, Na, K, Rb, and Cs; Me10 CB[5]=decamethylcucurbit[5]uril) hybrid solid materials have been successfully synthesized for the first time through a simple diffusion method. These as-prepared hybrid solids have been applied as phosphine-free precatalysts for Heck cross-coupling reactions with excellent catalytic performance and good recyclability. In the processes of the catalytic reactions, the activated Pd(II) species were released from the crystalline hybrid precatalysts and transformed into catalytically active Pd nanoparticles, which have been demonstrated as key to carry on the catalytic reactions for the recoverable precatalysts MPdMe10 CB[5] (M=K, Rb, and Cs). It has also been rationalized that the introduction of different alkali metals afforded crystalline hybrid precatalysts with different crystal structures, which are responsible for their diversified stability and reusability presented in Heck reactions.

Self-assembly of polyoxometalate-thionine multilayer films on magnetic microspheres as photocatalyst for methyl orange degradation under visible light irradiation.

(PW(12)-TH)(n) multilayer films (PW(12)=PW(12)O(40)(3-), TH=thionine) were deposited successfully on core-shell structured Fe(3)O(4)@SiO(2) magnetic microspheres through layer-by-layer (LbL) self-assembly method. The physical and photocatalytic properties of such magnetic microspheres coated with (PW(12)-TH)(n) films have been characterized by SEM, FTIR, and UV-vis spectra. The microspheres exhibit better photocatalytic activity toward the degradation of methyl orange (MO) under visible light irradiation than the quartz slides support. In addition, the use of magnetic support guarantees facile, clean, fast, and efficient separation of the photocatalyst after the degradation of MO. Such catalysts can be reused several times and display good reproducibility by magnetic separation.

Platinum nanoparticles stabilized by cucurbit[6]uril with enhanced catalytic activity and excellent poisoning tolerance for methanol electrooxidation.

Three sub-10 nm platinum nanoparticles (PtNPs) with distinctive morphologies were developed by using cucurbit[6]uril (CB[6]) as stabilizing agent and support. Both the size and shape of the PtNPs were simultaneously controlled by tuning the reducing agents. The prepared NPs have been comprehensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and cyclic voltammetry. On account of the presence of CB[6] and its unique structural features, the as-prepared PtNPs are homogeneous in morphologies and exhibit higher activities toward methanol electrooxidation than commercial Pt/C. CB[6] has the ability to bind small molecules that can promote CO oxidation, therefore, all the three PtNPs showed enhanced poisoning tolerance. Such unique abilities of CB[6] can even promote the poisoning tolerance of commercial Pt/C through simple physical mixing.

Mixed-phase PdRu bimetallic structures with high activity and stability for formic acid electrooxidation.

Aiming at investigating the effect of structure on electrocatalytic properties, Pd(50)Ru(50) nanoparticles (NPs) with three different structures were carefully designed in a one-pot polyol process for application in formic acid electrooxidation. The three structures are: (1) single-phase PdRu nanodendrites (denoted as PR-1), (2) a mixed-phase mixture of PdRu nanodendrites and monometallic Ru NPs (denoted as PR-2), and (3) a mixed-phase mixture of monometallic Pd and Ru NPs (denoted as PR-3). From PR-1 to PR-3, the structure was varied from single-phase to mixed-phase. The relative position of Ru was altered from completely Pd-connected (PR-1), to a mixture of Pd-connected and monometallic (PR-2), and completely monometallic (PR-3). All PdRu NPs outperform the commercial Pd/C. PR-2 exhibits the highest peak current density, but its stability is slightly lower than that of PR-3. When both the current density and the durability are taken into consideration, PR-2 is the best choice of catalyst for formic acid oxidation. It indicates that both the Pd-connected Ru NPs and monometallic Ru NPs in the mixed-phase PR-2 are essential to improve the electrocatalytic properties. Our study also illustrates that the electrochemical active surface area (ECSA) and hydrogen storage capacity of the as-prepared PdRu NPs are greatly enhanced after several hundred scans in formic acid, indicating the possibility for highly restorable catalysts in direct formic acid fuel cells.

Activation energy of the reaction between hexacyanoferrate (Ш) and thiosulfate ions catalyzed by platinum nanoparticles confined in nanometer space.

Pt nanoparticles (NPs) have been successfully encapsulated in SBA-15 mesoporous silica support. The silica was firstly functionalized by polyaminoamine (PAMAM) dendrimers with various generations and provided different nanometer space for Pt NPs. The growth of Pt NPs is restricted by the double confinement effect of PAMAM dendrimers and SBA-15 mesopores. The Pt NPs can be precisely controlled to localize inter- or intradendrimeric within SBA-15 tunnels. The different pore structures of Gn-PAMAM-SBA-15 (Gn-PS15) support have great influence on the catalytic performance of the encapsulated Pt NPs. The blocking structure of higher generation Gn-PS15 support debased the catalytic performance and increased the activation energy of reaction between Fe(CN)(6)(3-) and S(2)O(3)(2-) in a certain degree.

Facile synthesis of polyoxometalate-thionine composite via direct precipitation method and its photocatalytic activity for degradation of rhodamine B under visible light.

(TH)(3)PW(12) (TH=thionine, PW(12)=PW(12)O(40)(3-)) composite was prepared by direct precipitation of TH and PW(12). The (TH)(3)PW(12) was characterized via UV-vis spectrum, FT-IR, SEM, and BET surface area. PW(12) was intact during the precipitation process. The composite has a bar-like shape and relatively large surface area (Langmuir surface of (TH)(3)PW(12) was 31.59 m(2)g(-1), BET surface was 20.26 m(2)g(-1)). Using the material as the photocatalyst, rhodamine B (RhB) was efficiently bleached and mineralized under visible light irradiation (λ>420 nm). The kinetics of the photodecomposition follow the first-order reaction. The (TH)(3)PW(12) catalyst can be easily separated from the reaction system and has good stability for reuse.

Porous anionic, cationic, and neutral metal-carboxylate frameworks constructed from flexible tetrapodal ligands: syntheses, structures, ion-exchanges, and magnetic properties.

A series of coordination polymers with anionic, cationic, and neutral metal-carboxylate frameworks have been synthesized by using a flexible tetrapodal ligand tetrakis[4-(carboxyphenyl)oxamethyl] methane acid (H(4)X). The reactions between divalent transition-metal ions and H(4)X ligands gave [M(3)X(2)]·[NH(2)(CH(3))(2)](2)·8DMA (M = Co (1), Mn (2), Cd(3)) which have anionic metal-carboxylate frameworks with NH(2)(CH(3))(2)(+) cations filled in channels. The reactions of trivalent metal ions Y(III), Dy(III), and In(III) with H(4)X ligands afforded cationic metal-carboxylate frameworks [M(3)X(2)·(NO(3))·(DMA)(2)·(H(2)O)]·5DMA·2H(2)O (M = Y(4), Dy(5)) and [In(2)X·(OH)(2)]·3DMA·6H(2)O (6) with the NO(3)(-) and OH(-) serving as counterions, respectively. Moreover, a neutral metal-carboxylate framework [Pb(2)X·(DMA)(2)]·2DMA (7) can also be isolated from reaction of Pb(II) and H(4)X ligands. The charged metal-carboxylate frameworks 1-5 have selectivity for specific counterions in the reaction system, and compounds 1 and 2 display ion-exchange behavior. Moreover, magnetic property measurements on compounds 1, 2, and 5 indicate that there exists weak antiferromagnetic interactions between magnetic centers in the three compounds.

Development of a polyoxometallate-based photocatalyst assembled with cucurbit[6]uril via hydrogen bonds for azo dyes degradation.

A water insoluble cucurbit[6]uril-polyoxometallates (CB[6]-POMs) composite assembled from α-Keggin type polysilicontungstate anions and macrocycle cucurbit[6]uril (CB[6]) via hydrogen bonding has been synthesized as visible light active photocatalyst. The physical and photocatalytic properties of such photocatalyst have been fully characterized by PXRD, FTIR, TG, XPS, and UV/vis diffuse reflectance spectra. The catalyst shows a good photocatalytic activity towards the degradation of methyl orange (MO) under visible light irradiation and displays good reproducibility of photocatalytic degradation by a simple recycled procedure without obvious loss in catalytic activity, which is of great significance for practical use of the photocatalyst. In the photodegradation process, the {Ni-CB[6]}(n) chain of the photocatalyst acts as sensitizer and can be induced by visible light, meanwhile the POMs chain of the photocatalyst acts as electron acceptor and deposits the electron in its LUMO. The effects of various experimental parameters and the proposed mechanisms are discussed in detail.