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Palladium (Pd)-transition metal alloys have the potential to regulate the intermediate surface adsorption strength in oxygen reduction reactions (ORR), making them a promising substitute for platinum-based catalysts. Nonetheless, prolonged electrochemical cycling can lead to the depletion of transition metals, resulting in structural degradation and poor durability. Herein, the synthesis of alloy catalysts (Pd25%Te75%) containing Pd and the metalloid tellurium (Te) through a one-step reduction method is reported. Characterizations of powder X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy demonstrated both uniform dispersion and strong binding force of elements within the PdTe alloy, along with providing crystallographic details of associated compounds. Based on density functional theory calculations, PdTe had a more negative d-band center than that of pure Pd, which reduces the adsorption capacity between active sites and intermediates in the ORR, and therefore enhances reaction kinetics. The Pd25%Te75% exhibited excellent ORR activity, and its onset and half-wave potentials were â¼0.98 and â¼0.90 V, respectively, at 1600 rpm within the O2-saturated 1.0 M KOH. Significantly, accelerated durability tests achieved exceptional stability, and half-wave potential just decayed by 4 mV after 30000 consecutive cycles. Moreover, this study aims to promote the preparation of Pd and metalloid alloys for other energy conversion applications.
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Incorporating two organic ligands with different functionalities into a titanium-oxo cluster entity simultaneously can endow the material with their respective properties and provide synergistic performance enhancement, which is of great significance for enriching the structure and properties of titanium-oxo clusters (TOCs). However, the synthesis of such TOCs is highly challenging. In this work, we successfully synthesized a TBC4A-functionalized TOC, [Ti2(TBC4A)2(MeO)2] (Ti2; MeOH = methanol, TBC4A = tert-butylcalix[4]arene). By adjusting the solvent system, we successfully introduced 1,10-phenanthroline (Phen) and prepared TBC4A and Phen co-protected [Ti2(TBC4A)2(Phen)2] (Ti2-Phen). Moreover, when Phen was replaced with bulky 4,7-diphenyl-1,10-phenanthroline (Bphen), [Ti2(TBC4A)2(Bphen)2] (Ti2-Bphen), which is isostructural with Ti2-Phen, was obtained, demonstrating the generality of the synthetic method. Remarkably, Ti2-Phen demonstrates good stability and stronger light absorption, as well as superior photoelectric performance compared to Ti2. Density functional theory (DFT) calculations reveal that there exists ligand-to-core charge transfer (LCCT) in Ti2, while an unusual ligand-to-ligand charge transfer (LLCT) is present in Ti2-Phen, accompanied by partial LCCT. Therefore, the superior light absorption and photoelectric properties of Ti2-Phen are attributed to the existence of the unusual LLCT phenomenon. This study not only deeply explores the influence of Phen on the performance of the material but also provides a reference for the preparation of materials with excellent photoelectric performance.
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The development of heterostructured anode materials provides an effective approach for enhancing the electrochemical performance of sodium-ion batteries (SIBs). In this work, ab initio molecular dynamics simulations and first-principles calculations are employed to investigate the Na-ion intercalation and diffusion in MXene/graphene oxide heterostructures. The influence of graphene oxidation on interlayer spacing, Na-ion diffusion kinetics, and transport mechanisms is examined at an atomic scale. It has been observed that oxygen functional groups can increase the interspacing between adjacent layers, thereby improving the initial embedding of Na ions. However, overoxidation causes an obstructive effect on the ionic conduction channels. An appropriate oxidation degree enables optimal Na-ion migration kinetics while retaining structural integrity. Our simulation results provide crucial insights into the rational design of high-performance MXene-based anodes for SIBs with excellent capacity and cycling stability.
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Highly pure Rh2P nanoparticles on N,P-codoped carbon were synthesized by a simple "mix-and-pyrolyze" method using one kind of low-cost nucleotide as the carbon, nitrogen and phosphorus source, which exhibits excellent bifunctional activity for the hydrogen reduction and hydrazine oxidation reactions, achieving energy-efficient hydrogen production.
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Designing and synthesizing well-defined crystalline catalysts for the photocatalytic oxidative coupling of amines to imines remains a great challenge. In this work, a crystalline dumbbell-shaped titanium oxo cluster, [Ti10O6(Thdc)(Dmg)2(iPrO)22] (Ti10, Thdc = 2,5-thiophenedicarboxylic acid, Dmg = dimethylglyoxime, iPrOH = isopropanol), was constructed through a facile one-pot solvothermal strategy and treated as a catalyst for the photocatalytic oxidative coupling of amines. In this structure, Thdc serves as the horizontal bar, while the {Ti5Dmg} layers on each side act as the weight plates. The molecular structure, light absorption, and photoelectrochemical properties of Ti10 were systematically investigated. Remarkably, the inclusion of the Thdc ligand, with the assistance of the Dmg ligand, broadens the light absorption spectrum of Ti10, extending it into the visible range. Furthermore, the effective enhancement of charge transfer within the Ti10 was achieved with the successful incorporation of the Thdc ligand, as opposed to PTC-211, where terephthalic acid replaces the Thdc ligand, while maintaining consistency in other aspects of Ti10. Building on this foundation, Ti10 was employed as a heterogeneous molecular photocatalyst for the catalytic oxidative coupling reaction of benzylamine (BA), demonstrating very high conversion activity and selectivity. Our study illustrates that the inclusion of ligands derived from Thdc enhances the efficiency of charge transfer in functionalized photocatalysts, significantly influencing the performance of photocatalytic organic conversion.
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The controlled synthesis of titanium-oxo clusters (TOCs) completely stabilized by organic dye ligands with high stability and superior light absorption remains a significant challenge. In this study, we report the syntheses of three atomically precise catechol (Cat)-functionalized TOCs, [Ti2(Cat)2(OEgO)2(OEgOH)2] (Ti2), [Ti8O5(Cat)9(iPrO)4(iPrOH)2] (Ti8), and [Ti16O8(OH)8(Cat)20]·H2O·PhMe (Ti16), using a solvent-induced strategy (HOEgOH = ethylene glycol; iPrOH = isopropanol; PhMe = toluene). Interestingly, the TiO core of Ti16 is almost entirely enveloped by catechol ligands, making it the first all-catechol-protected high-nuclearity TOC. In contrast, Ti2 and Ti8 have four weakly coordinated ethylene glycol ligands and six weakly coordinated iPrOH ligands, respectively, in addition to the catechol ligands. Ti16 is visually evident in its distinctively black appearance, which belongs to black TOCs (B-TOCs) and exhibits an ultralow optical band gap. Furthermore, Ti16 displays exceptional stability in various media/environments, including exposure to air, solvents, and both acidic and alkaline aqueous solutions due to its comprehensive protection by catechol ligands and rich intra-cluster supramolecular interactions. Ti16 has superior photoelectric response qualities and photothermal conversion capabilities compared to Ti2 and Ti8 due to its ultralow optical band gap and remarkable stability. This discovery not only represents a huge step forward in the creation of all-catecholate-protected B-TOCs with ultralow optical band gaps and outstanding stability, but it also gives key valuable mechanistic insights into their photothermal/electric applications.
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Modifying the surface of a catalyst with heteroatoms can regulate the interfacial atomic valence state and adjust the charge distribution, which is promising for obtaining desirable platinum carbon catalyst (Pt/C)-matched oxygen reduction reaction (ORR) catalytic performance. Here, we developed an efficient method to access O-rich crystalline interfacial-exposed palladium-tin alloy (111) crystal surfaces [Pd3Sn (111)] for highly efficient ORR via direct reduction of Pd/Sn metal salt species that are well dispersed in a nitrogen, phosphorus-doped carbonaceous (NPC) substrate. In addition to the other materials, preembedded Pd/Sn metal salt species in NPC control the release of metal sources upon reduction in the liquid phase, resulting in the grafting of an as-prepared PdSn alloy with many merits, such as efficient electron conduction, short-range crystallinity and increased crystal interface exposure. The presence of a considerable quantity of oxygen atoms at the interface of small-sized PdSn alloys on NPC substrates has been methodically verified by powder X-ray diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy characterizations. The PdSn-O sample exhibited excellent ORR activity, achieving an onset potential of â¼0.99 V and a half-wave potential of â¼0.88 V at 1600 rpm in O2-saturated 1.0 M KOH. Density functional theory simulations of pure Pd, Pd-O, the PdSn alloy and PdSn-O suggest that interfacial oxygen atom modification is responsible for the significantly improved ORR activity. The assembled zinc-air battery provides a high specific power of 218.9 mW cm-2 and a specific capacity of 810.6 mAh gZn-1. Our approach has the potential to stimulate the preparation of O-rich crystalline interfacial-exposed alloy compounds for other energy conversion applications.
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Pillaring MXene with organic molecules is an effective approach to expand the interlayer spacing and increase the accessible surface area for enhanced performance in energy storage applications. Herein, molecular dynamics simulations are employed to explore the pillaring effect of six organic molecules on Ti3C2O2. The interlayer spacing and structural characteristics of MXene after the insertion of different organic molecules are examined, and the influence of the type and quantity of organic molecules on the pillared MXene structure is systematically investigated. The results demonstrate that the inserted molecules are influenced by interactions between MXene layers, resulting in a thinner morphology. Effective pillar support on MXene is achieved only when a specific quantity of organic molecules is inserted between the layers. Furthermore, different organic molecules occupy distinct surface areas on MXene when acting as pillars. Pillaring molecules with a Pi-conjugated ring structure require a larger surface area on MXene, whereas those with a branched structure occupy a smaller surface area. Additionally, organic molecules containing oxygen functional groups tend to aggregate due to hydrogen bonding, impeding their diffusion within MXene sheets. Considering the interlayer expansion of MXene, surface area occupation, and diffusion characteristics, the isopropylamine demonstrates the most favorable pillaring effect on MXene. These findings provide valuable insights into the design and application of pillared MXenes in energy storage and other applications. Further studies on the properties and applications of the optimized pillared MXene structures will be conducted in the future.
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The low-potential hydrazine oxidation reaction (HzOR) can replace the oxygen evolution reaction (OER) and thus assemble with the hydrogen evolution reaction (HER), consequently achieving energy-saving hydrogen (H2) production. Notably, developing sophisticated bifunctional electrocatalysts for HER and HzOR is a prerequisite for efficient H2 production. Alloying noble metals with eligible non-precious ones can increase affordability, catalytic activity, and stability, alongside rendering bifunctionality. Herein, RuNi alloy deposited onto carbon (RuNi/C) was directly prepared by a simple and highly practical co-reduction method, showing excellent performance for HER and HzOR. Interestingly, to achieve 10 mA cm-2, RuNi/C only required an ultralow potential of 24 mV for HER, on par with commercial 20 wt% platinum in carbon (Pt/C), and -65 mV for HzOR, surpassing most reported counterparts. Moreover, the two-electrode electrolyzer only required small operation voltages of 57.8 and 327 mV to drive 10 and 100 mA cm-2, respectively. Driven by a homemade hydrazine (N2H4) fuel cell and solar panel, appreciable H2 yields of 1.027 and 1.406 mmol h-1 were achieved, respectively, exhibiting the energy-saving advantages alongside robust practicability. Moreover, theoretical calculations revealed that alloying with Ru endows bifunctional Ni sites not only with a lower H2O dissociation barrier but also with more favorable H* adsorption alongside the reduced energy barrier between HzOR intermediates.
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Multifunctional photochromic coordination polymers (CPs) have shown great potential in many areas, like molecular switches, anticounterfeiting, magnetics, and optoelectronics. Although multifunctional photochromic CPs can be obtained by introducing photoresponsive functional units or by exploiting the synergy effect of each component, relatively limited photochromic ligands hinder the development of various multifunctional photochromic CPs. In this work, we reported two multifunctional coordination polymers {[Zn(bpdo)(fum)(H2O)2]}n (1) and {[Mn(bpdo)(fum)(H2O)2]}n (2) based on an easily accessible but underestimated photoactive molecule 4,4'-bipyridine-N,N'-dioxide (bpdo). Compound 1 exhibits photochromism and white-light emission with an ultra-high color rendering index (CRI) of 92.1. Interestingly, compound 1 could emit intrinsic white light in the crystalline state upon UV irradiation both before and after photochromism. Meanwhile, compound 2 displays photochromic and photomagnetic properties, induced by the photogenerated radicals via a photoinduced electron transfer mechanism.
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Two dimensional zeolites have drawn a lot of attention due to their structural diversity and chemical composition, which can be used to obtain 3D zeolites, for which there is no direct synthesis. Here, a new layer silicate zeolite L was synthesized using the N, N-dimethyl-(2-methyl)-benzimidazolium as the organic structure-directing agent (OSDA) in the presence of fluoride. Structure determination by single-crystal X-ray diffraction reveals that the pure silica precursor with five-ring pores in the crystalline sheets is composed of the rth layer stacking along the (001) direction in an AAAA sequence with SDA+ cations and F- residing within the interlayer spaces. Variable temperature powder X-ray diffraction (PXRD) results showed that the new layer could transform into a 3D RTH topology structure at 350 °C via 2D-3D topotactic transformation. Furthermore, a new 3D zeolite material is obtained by treating the original layer with a diethoxydimethylsilane agent under hydrochloric acid condition (HCl-DEDMS). Based on the PXRD results and the original layer structure, the new 3D zeolite structure expanding the rth layer with another Si atom is constructed, which possesses a 10×8×6 channel system. It displays a high BET surface area of 188â cm3 /g with an external surface area of 130â cm3 /g. The structure and textural properties pave a way for potential catalytic applications. The research not only provides a new layered zeolite, broadening the 2D zeolite framework types, but also allows for the discovery of a new stable 3D zeolite expanding the RTH structure with Si atom, which hasn't been reported yet.
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The morphology and porosity of zeolites have an important effect on adsorption and catalytic performance. In the work, simple inorganic salts, i.e., Na salts were used to synthesize MWW zeolite using the organic compound 1-Butyl-2,3-dimethyl-1H-imidazol-3-ium hydroxide as a structure-directing agent and the morphology was regulated by the alkali metals. The sample synthesized without Na salts shows a dense hexagon morphology, while different morphologies like ellipsoid, wool ball, and uniform hexagon appear when using NaOH, Na2CO3, and NaHCO3, respectively. Moreover, the impact of Na salts on the induction, nucleation, and the evolution of crystal growth was studied. Different kinds of Na salts have a different impact on the crystalline induction time in the order of NaHCO3 (36 h) < Na2CO3 (72 h) = NaOH (72 h). Meanwhile, the crystalline mechanism with the cooperation of inorganic salts and the organic SDAs is proposed. NaOH- and Na2CO3-MWW zeolite crystallized with a network of hydrogel via the nonclassical pathway in the system; however, the product is synthesized via a classical route in the NaHCO3 environment. This work provides information about MWW zeolite crystallization and modulating diverse morphologies by adjusting the process.
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Pillared MXenes with large interlayer spacing have shown great potential as an anode material for sodium-ion batteries (SIBs). To better understand the underlying mechanism of the pillar effect in enhancing the electrochemical performance, first-principles calculations were used to investigate the adsorption and diffusion of Na in MXenes (Ti2CO2 and Ti3C2O2), as well as the mechanical properties of the system under different MXenes layer spacings. The results showed that when the MXene layer spacing was â¼4 Å, the strongest adsorption of Na on MXenes was achieved due to the interlayer synergy effect. However, when the MXene layer spacing was greater than 5 Å, double Na-atomic layer adsorption would be formed, which increased the Na storage capacity. Interestingly, the diffusion of Na was not only affected by the interlayer spacing of MXenes, but also by the interlayer stacking mode of MXenes. Moreover, it was found that when the MXene layer spacing was more than 8 Å, the sodium storage properties basically did not change significantly. The optimal layer spacing for Ti2CO2 and Ti3C2O2 was predicted to be 7 and 6 Å, respectively. This work provides valuable theoretical guidance for developing high-performance anode materials for SIBs.
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The construction of cluster-based crystalline chalcogenide structures through the traditional solvothermal method relies on synergistic control of precursors, template cations and auxiliary solvents. Generally, the combination of metal precursors plays a crucial role in controlling the size of clusters, while organic templates and auxiliary solvents usually contribute to the type of clusters and architecture of the framework. Decades of synthetic efforts have been mainly devoted to expanding organic amine templates for constructing new structures. However, the important role of auxiliary solvents in enriching the chalcogenide family is usually disregarded. Reported here are several new crystalline In-Se compounds (ISP-1 to 4) with different dimensions, obtained by elaborately regulating auxiliary solvents under the direction of the same organic template, piperidine. Of these four structures, ISP-1 is constructed by irregular supertetrahedral clusters, giving a novel 2D structure with a corner-shared single Se atom and In2Se3 five-member ring as linkers; ISP-2 has a 1D structure composed by interlinked In2Se3 five-member rings; ISP-4 is constructed by supertetrahedral T2 clusters exhibiting an uncommon zeolite-like mog network.
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One common iridium(III) complex was employed to facilely prepare ultrafine Ir nanoclusters embedded in porous N-doped carbon, which displayed significant bifunctional activity for both hydrogen evolution and hydrazine oxidation under alkaline conditions, enabling energy-efficient hydrogen production.
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The high dependence of cathodic oxygen reduction reaction on precious Pt catalysts hinders the large-scale commercialization of proton exchange membrane (PEM) fuel cells, while the most promising alternative FeNC catalyst cannot achieve satisfying fuel cell performance yet. By considering the different requirements of atomically dispersed FeNC catalyst on the mass-transfer structure from that of nanoparticle Pt-based catalysts, this work develops a "porogen-in-resin" strategy to approach the Fe, N-doped interconnected porous carbon sheet (ip-FeNCS) catalyst. Three-dimensional (3D) interconnected porous structure and two-dimensional (2D) nanosheet morphology are therefore facilely combined in ip-FeNCS to simultaneously achieve the requirements on the transfer of reactants and accessibility of FeN active sites. Not only great ORR activity can be achieved under both alkaline and acid conditions but also the ip-FeNCS catalyst shows superb activity in practical PEM fuel cells from the high power output to 413 mW/cm2. Such fuel cell performance places this ip-FeNCS catalyst among the best FeNC ORR catalysts reported thus far. This work presents a general and facile approach toward the mass-transfer structure engineering of atomically dispersed carbon catalysts for practical PEM fuel cell applications.
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Ultrathin metallic iridium nanosheets (â¼4 nm) were synthesized using MIL-88A as the sacrificing template at room temperature. Ir-NS shows superior and stable water splitting performance in an acidic medium.
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Natural DNA was employed for the first time as a phosphorization agent and carbon source to controllably synthesize a RuP2/N,P-codoped carbon composite by a simple "mix-and-pyrolyze" strategy, which displays higher activity for alkaline and acidic HER and neutral activity compared to Pt/C together with outstanding durability.
Asunto(s)
ADN de Cadena Simple/química , Grafito/química , Hidrógeno/química , Rutenio/química , Animales , Catálisis , Concentración de Iones de Hidrógeno , Nitrógeno/química , Fósforo/química , Espectroscopía de Fotoelectrones , Salmón/genéticaRESUMEN
The electronically interacted Co3O4/WS2 with a maximum power density of 174 mW cm-2, 2.3 fold better than Pt/C-IrO2, shows its superiority as an oxygen electrode for rechargeable zinc-air batteries.
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To realize the large-scale application of fuel cells, it is still a great challenge to improve the performance and reduce the cost of cathode catalysts towards oxygen reduction reaction (ORR). In this work, carbon-supported ordered Pt3Mn intermetallic catalysts were prepared by thermal annealing electrospun polyacrylonitrile nanofibers containing Platinum(II) acetylacetonate/ Manganese(III) acetylacetonate. Compared with its counterparts, the ordered Pt3Mn intermetallic obtained at 950 °C exhibits a more positive half-potential and higher kinetic current density during the ORR process. Benefiting from their defined stoichiometry and crystal structure, the Mn atoms in Pt3Mn intermetallic can modulate well the geometric and electronic structure of surface Pt atoms, endowing Pt3Mn catalyst with an enhanced ORR catalytic activity. Moreover, it also has a better catalytic stability and methanol tolerance than commercial Pt/C catalyst. Our study provides a new strategy to fabricate a highly active and durable Pt3Mn intermetallic electrocatalyst towards ORR.