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A coupling catalyst of highly dispersed N, P co-doped carbon frames (NPCFs) anchored with Fe single atoms (SAs) and Fe

Summary The electrochemical direct synthesis of hydrogen peroxide (H2O2) is significant but still challenging because of the lack of highly selective and active catalysts. Here, we report the synthesis of hollow nanospheres constructed by atomically dispersing platinum in amorphous CuSx support (h-Pt1-CuSx) with a high concentration of single atomic Pt sites (24.8 at%), and this catalyst can consistently reduce O2 into H2O2 with selectivity of 92%–96% over a wide potential range of 0.05–0.7 V versus RHE in HClO4 electrolyte. Scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy confirmed the atomically isolated form of Pt with a low valance of +0.75. An electrochemical device that can synthesize H2O2 directly from H2 and O2 is fabricated with H2O2 productivity as high as 546 ± 30 mol kgcat−1 h−1. The well-defined and high-concentration single atomic Pt sites result in ultrahigh productivity of H2O2.

Multi-shelled hollow structured materials featuring large void volumes and high specific surface areas are very promising for a variety of applications. However, controllable synthesis of multi-shelled hollow structured intermetallic compounds remains a formidable challenge due to the high annealing temperature commonly required for the formation of intermetallic phases. Here, a topological self-template strategy was developed to solve this problem. Using this strategy, we prepared well-defined multi-shelled intermetallic Ni3Ga hollow microspheres (Ni3Ga-MIHMs) as disclosed by the HAADF-STEM, HRTEM, and EDS characterizations, and the BET specific surface areas of them measured as much as 153.4 m2 g−1. XRD and EXAFS spectral characterizations revealed the atomically ordered intermetallic phase nature of the Ni3Ga-MIHMs. The selective hydrogenation of acetylene catalytic evaluation results further demonstrated excellent catalytic properties of the Ni3Ga-MIHMs, which results from the more energetically facile reaction pathway for acetylene hydrogenation and ethylene desorption over it as revealed by DFT calculations. Besides, this strategy is also extendable to synthesize other multi-shelled intermetallic Ni3Sn4 hollow microspheres, and is expected to open up new opportunities for rational design and preparation of novel structured and highly efficient intermetallics.

Hollow PdO-Co3O4 nano-dodecahedrons with moderate catalytic activity were designed as electrocatalysts for Li-O2 batteries, and not only reduce the overpotentials effectively but also improve the reversibility of the ORR and OER, and cycle for more than 90 cycles stably with extremely low overpotentials.

Photocatalysis based on the use of semiconducting materials is an emerging alternative to conventional thermochemical catalysis, and it has the potential to promote chemical synthesis under greener and milder conditions. However, heterogeneous photocatalytic organic reactions are still in their infancy, limited by the low-efficiency carrier separation of the currently available photocatalytic materials. Here, we report photochromic Bi2WO6–x/amorphous BiOCl (p-BWO) nanosheets, which, distinct from pristine Bi2WO6, show blue colouration upon visible light irradiation and are bleached by atmospheric oxygen. Studies on the microscopic structure of the material reveal the existence of abundant W(vi)O6–x units, which serve as the sites for the fast and continuous consumption of photogenerated electrons, thereby effectively facilitating the separation of electron–hole pairs. The prepared composite features a remarkable enhancement in performance for the photocatalytic oxidation of toluene with a conversion rate 166-fold higher compared with that of pristine Bi2WO6. Despite its potential, the visible light-triggered photocatalytic oxidation of toluene remains difficult due to the lack of efficient and scalable catalytic strategies. Now, a photochromic Bi2WO6–x/amorphous BiOCl composite is reported with the ability to oxidize toluene into benzaldehyde and benzoic acid with outstanding rates and quantum efficiencies.

We developed a strategy based on coordination polymer to synthesize singleatom site Fe/N and S-codoped hierarchical porous carbon (Fe1/N,S-PC). The as-obtained Fe1/N,S-PC exhibited superior oxygen reduction reaction (ORR) performance with a half-wave potential (E1/2, 0.904 V vs. RHE) that was better than that of commercial Pt/C (E1/2, 0.86 V vs. RHE), single-atom site Fe/N-doped hierarchical porous carbon (Fe1/N-PC) without S-doped (E1/2, 0.85 V vs. RHE), and many other nonprecious metal catalysts in alkaline medium. Moreover, the Fe1/N,S-PC revealed high methanol tolerance and firm stability. The excellent electrocatalytic activity of Fe1/N,S-PC is attributed to the synergistic effects from the atomically dispersed porphyrin-like Fe-N4 active sites, the heteroatom codoping (N and S), and the hierarchical porous structure in the carbon materials. The calculation based on density functional theory further indicates that the catalytic performance of Fe1/N,S-PC is better than that of Fe1/N-PC owing to the sulfur doping that yielded different rate-determining steps.

Developing an efficient single-atom material (SAM) synthesis and exploring the energy-related catalytic reaction are important but still challenging. A polymerization-pyrolysis-evaporation (PPE) strategy was developed to synthesize N-doped porous carbon (NPC) with anchored atomically dispersed Fe-N4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe-N4 site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn-air battery devices containing the Fe-N4 SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.

The promoting effect of sulfur sources is an intriguing but poorly understood phenomenon. Herein, we studied the treatment of PdCu bimetallic nanoparticles (NPs) with different amounts of sulfur powder. Low-level sulfidation led to the generation of a Pd30Cu10S9 NP catalyst consisting of surface enriched Pd NPs, electron deficient Pd and Cu, as well as zero valence sulfur. The Pd30Cu10S9 NP catalyst showed pronouncedly enhanced activity and selectivity in the semihydrogenation of alkynes. Our study revealed for the first time a possible cause for the promoting effect of sulfur at the atomic level, suggesting a new strategy in catalyst design.

The development of low-cost, efficient, and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we made a highly reactive and stable isolated single-atom Fe/N-doped porous carbon (ISA Fe/CN) catalyst with Fe loading up to 2.16 wt %. The catalyst showed excellent ORR performance with a half-wave potential (E1/2) of 0.900 V, which outperformed commercial Pt/C and most non-precious-metal catalysts reported to date. Besides exceptionally high kinetic current density (Jk) of 37.83 mV cm−2 at 0.85 V, it also had a good methanol tolerance and outstanding stability. Experiments demonstrated that maintaining the Fe as isolated atoms and incorporating nitrogen was essential to deliver the high performance. First principle calculations further attributed the high reactivity to the high efficiency of the single Fe atoms in transporting electrons to the adsorbed OH species.

A highly efficient and selective bimetallic Pd0.88Co0.12 nanoparticle catalyst was developed for the direct N-formylation of amines by carbon monoxide. This catalyst is compatible with a wide range of substrates, affording various synthetically useful formamides under practical and mild reaction conditions.

RuCu nanocages and core–shell Cu@Ru nanocrystals with ultrathin Ru shells were first synthesized by a one-pot modified galvanic replacement reaction. The construction of bimetallic nanocrystals with fully exposed precious atoms and a high surface area effectively realizes the concept of high atom-efficiency. Compared with the monometallic Ru/C catalyst, both the RuCu nanocages and Cu@Ru core–shell catalysts supported on commercial carbon show superior catalytic performance for the regioselective hydrogenation of quinoline toward 1,2,3,4-tetrahydroquinoline. RuCu nanocages exhibit the highest activity, achieving up to 99.6% conversion of quinoline and 100% selectivity toward 1,2,3,4-tetrahydroquinoline.

In this Communication, we present the integration of synergetic designs into high-quality, well-defined Cu1.94S-ZnxCd1-xS heteronanorods (0 ≤ x ≤ 1) for enhanced photocatalytic hydrogen evolution. These heteronanorods possess two light absorbers, intimate heterointerfaces, tunable band gaps over a wide range, and uniform one-dimensional morphology. As verified by experimental and density functional theory studies, these heteronanorods with continuous composition adjustment fully exploit the benefits of both interfacial charge separation and optimized band alignments. Even without any cocatalysts, Cu1.94S-Zn0.23Cd0.77S heteronanorods exhibit efficient hydrogen production activity (7735 μmol h(-1) g(-1)) under visible-light irradiation (λ420 nm), representing a 59-fold enhancement compared with the pristine CdS catalyst. Meanwhile, deposition of a Pt cocatalyst on the Cu1.94S-ZnxCd1-xS surface substantially enhances the hydrogen production performance (13 533 μmol h(-1) g(-1)) with an apparent quantum efficiency of 26.4% at 420 nm, opening up opportunities to promote the overall photocatalytic performance using rationally designed nanostructures.

We have exploited a new and distinctive combination method that “disperses” elemental Pd into CuS nanoplates. Pd was successfully dispersed by means of the concomitant transformation of CuS into an amorphous sulfide, which formed an intimate metal–sulfide contact via cation exchange and underwent a subsequent reduction. A series of such Pd-dispersed CuS hetero-nanoplates were synthesized with tailored proportions and compositions. By efficient utilization of noble metal atoms and stable anchored active sites, the optimal catalytic performance for the semihydrogenation of phenylacetylene, a probe reaction, was achieved with high selectivity, activity, and stability. We believe that the synthetic strategy described in our study is a feasible means of developing effective metal–sulfide catalysts for organic reactions.

Bimetallic PdAu nanocrystals with different component ratios were obtained to investigate alkyne homocoupling. We found that the synergistic effect of Pd and Au plays an important role in the reaction. Alkynes with a variety of substituent groups could efficiently be converted into the corresponding 1,3-diynes through oxidative coupling.

The Well-defined multi-shelled intermetallic Ni3Ga hollow microspheres were firstly prepared with attractive properties., Multi-shelled hollow structured materials featuring large void volumes and high specific surface areas are very promising for a variety of applications. However, controllable synthesis of multi-shelled hollow structured intermetallic compounds remains a formidable challenge due to the high annealing temperature commonly required for the formation of intermetallic phases. Here, a topological self-template strategy was developed to solve this problem. Using this strategy, we prepared well-defined multi-shelled intermetallic Ni3Ga hollow microspheres (Ni3Ga-MIHMs) as disclosed by the HAADF-STEM, HRTEM, and EDS characterizations, and the BET specific surface areas of them measured as much as 153.4 m2 g–1. XRD and EXAFS spectral characterizations revealed the atomically ordered intermetallic phase nature of the Ni3Ga-MIHMs. The selective hydrogenation of acetylene catalytic evaluation results further demonstrated excellent catalytic properties of the Ni3Ga-MIHMs, which results from the more energetically facile reaction pathway for acetylene hydrogenation and ethylene desorption over it as revealed by DFT calculations. Besides, this strategy is also extendable to synthesize other multi-shelled intermetallic Ni3Sn4 hollow microspheres, and is expected to open up new opportunities for rational design and preparation of novel structured and highly efficient intermetallics.

We successfully prepared Fe and Co isolated single atoms on metal-organic framework derived nitrogen-doped carbon (FeCo-ISAs/CN) by an adsorption-calcination strategy. The obtained FeCo-ISAs/CN exhibited top-level catalytic reactivity for the alkaline oxygen reduction reaction (ORR) with a half-wave potential of 0.920 V, which was 70 mV more positive than that of commercial Pt/C. Moreover, the catalyst was durable and showed negligible activity decay in the alkaline ORR during 5000 voltage cycles.

Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells., Development of fuel cells and metal-air batteries is hindered by electrocatalyst performance, which can be enhanced with uniform and atomically dispersed active sites. Here the authors report an iron-based electrocatalyst for oxygen reduction in cathodes for a zinc-air battery and a hydrogen-air fuel cell.

Aqueous Ag:ZnCdS quantum dots (QDs) with pure, color-tunable fluorescence were prepared based on co-nucleation doping strategy by using a highly reactive S powder precursor, which was reduced by NaBH 4 at high temperature of 180 °C in a closed hydrothermal autoclave. For a meaningful comparison, thiourea as a relatively low reactive precursor was employed to test the advantages of this highly reactive S powder precursor in synthetic chemistry. The influences of various experimental variables, including the Zn/Cd ratio and Ag-doping concentration, on the optical properties of Ag:ZnCdS QDs were systematically investigated. The color-tunable quarternary Ag:ZnCdSeS QDs were also successfully prepared via the variation of Se/S precursor ratio based on the similar reactivity of the Se and S powder precursors. Further, the highly efficient Ag:ZnCdS/ZnS and Ag:ZnCdSeS/ZnS core/shell QDs were constructed by the deposition of the ZnS shell around the crude Ag:ZnCdS and Ag:ZnCdSeS core QDs. The results indicated that this facile synthetic route would provide a versatile approach for preparation of other aqueous multinary metal chalcogenide QDs.

We have developed two strategies to optimize Pd catalysts. On one hand, Ag was introduced into Pd and then they were applied to the selective hydrogenation of citral under mild conditions. The addition of metallic Ag could tune the selectivity of Pd and made it suitable for the selective hydrogenation of the conjugated double bond. The selectivity of citronellal increased from 0 (for Pd/C and Pd0.7Ag0.3/C) to 96 % (for Pd0.4Ag0.6/C) as the Ag content increased. On the other hand, the addition of SnO2 made the Pd catalysts more inclined to activate the C=O bond and gave better performance for the hydrogenation of the conjugated double bond compared with the corresponding Pd–Ag catalysts. The selectivity of citronellal increased from 0 (for Pd0.7Ag0.3/C) to 76 % (for Pd0.7Ag0.3–SnO2/C was used) after the addition of SnO2. On the basis of these results, we developed a catalyst (Pd0.6Ag0.4–SnO2/C) with the best catalytic performance for the selective hydrogenation of citral (the conversion of citral reached 99 %, and the selectivity was up to 96 %).

Heteroatom-doped Fe-NC catalyst has emerged as one of the most promising candidates to replace noble metal-based catalysts for highly efficient oxygen reduction reaction (ORR). However, delicate controls over their structure parameters to optimize the catalytic efficiency and molecular-level understandings of the catalytic mechanism are still challenging. Herein, a novel pyrrole-thiophene copolymer pyrolysis strategy to synthesize Fe-isolated single atoms on sulfur and nitrogen-codoped carbon (Fe-ISA/SNC) with controllable S, N doping is rationally designed. The catalytic efficiency of Fe-ISA/SNC shows a volcano-type curve with the increase of sulfur doping. The optimized Fe-ISA/SNC exhibits a half-wave potential of 0.896 V (vs reversible hydrogen electrode (RHE)), which is more positive than those of Fe-isolated single atoms on nitrogen codoped carbon (Fe-ISA/NC, 0.839 V), commercial Pt/C (0.841 V), and most reported nonprecious metal catalysts. Fe-ISA/SNC is methanol tolerable and shows negligible activity decay in alkaline condition during 15 000 voltage cycles. X-ray absorption fine structure analysis and density functional theory calculations reveal that the incorporated sulfur engineers the charges on N atoms surrounding the Fe reactive center. The enriched charge facilitates the rate-limiting reductive release of OH* and therefore improved the overall ORR efficiency.

High-quality, pure, and color-tunable Ag:ZnCdS quantum dots (d-dots) are prepared by optimization of the experimental conditions including Ag-doping concentration and Zn/Cd precursor ratio. Highly emissive Ag:ZnCdS/ZnS core/shell d-dots with photoluminescence quantum yield (PL QY) as high as 58% are constructed in situ by the growth of a ZnS shell around the crude Ag:ZnCdS solution, which is the highest PL QY reported to date for Ag-based semiconductor d-dots. The emission color of a Ag:ZnCdS d-dot can be tuned toward a larger red region by simple Se treatment at high temperature (220–260 °C). With Se treatment, Ag:ZnCdS alloyed d-dots are transformed into Ag:ZnCdSSe alloyed d-dots, and the corresponding optical changes of d-dots in this process are investigated systematically. This strategy provides a versatile approach for the preparation of other multinary semiconductor nanocrystals.

The search for a low-cost, ultrastable, and highly efficient non-precious metal catalyst substitute for Pt in the oxygen reduction reaction (ORR) is extremely urgent, especially in acidic media. Herein, we develop a template-assisted pyrolysis (TAP) method to obtain a unique Co catalyst with isolated single atomic sites anchored on hollow N-doped carbon spheres (ISAS-Co/HNCS). Both the single sites and the hollow substrate endow the catalyst with excellent ORR performance. The half-wave potential in acidic media approaches that of Pt/C. Experiments and density functional theory have verified that isolated Co sites are the source for the high ORR activity because they significantly increase the hydrogenation of OH* species. This TAP method is also demonstrated to be effective in preparing a series of ISAS-M/HNCS, which provides opportunities for discovering new catalysts.

Based on a phosphine-free route and the nucleation-doping strategy, Mn-doped CdSe nanocrystals (d-dots) with zinc-blende structure were successfully synthesized by facilely controlling the reaction temperature. The evolution of the UV–vis and PL spectra exhibited the distinctly different results for the nanocrystals synthesized at 160,180 and 200 °C. The products were Mn:CdSe d-dots at 160 °C, but undoped CdSe nanocrystals at 200 °C. We proposed a possible mechanism that Mn ions were rapidly ejected from the host CdSe lattice if the doping temperature was too high. Combining with TEM and spectral results of the resulting nanocrystals, the mechanism was further confirmed powerfully by the annealing for the presynthesized and purified Mn:CdSe nanocrystals.

Intermetallic Nix My (M = Ga and Sn) nanocrystals with uniform particle size and controlled composition are successfully synthesized via a solution-based co-reduction strategy. The as-obtained nanocrystals are crystalline and structurally ordered. The active-site isolation and modified electronic structure are responsible for the excellent catalytic performance for alkyne semi-hydrogenation of the as-obtained non-precious catalysts.

Aqueous Ag:ZnCdS quantum dots (QDs) are prepared based on a co-nucleation doping strategy using aqueous solutions of Cd(OAc)2, Zn(OAc)2 (in presence of mercaptopropionic acid; Cd:Zn molar ratio of 1:1), and AgNO3 at pH 7 to which a reactive S (and Se) powder precursor (hydrothermal S (Se) solution in presence of NaBH4) is given (autoclave, 180 °C, 2 h).

Correction for ‘Isolated Fe and Co dual active sites on nitrogen-doped carbon for a highly efficient oxygen reduction reaction’ by Diyang Zhang et al., Chem. Commun., 2018, DOI: 10.1039/c8cc00988k.

A new sulfur precursor with a highly reactive chemical nature was prepared with S powder and NaBH₄ at the high temperature of 180 °C in a closed autoclave and made it possible to carry out the synthesis of high quality metal sulfide nanocrystals (NCs) with diverse composition and structure. Using this new sulfur source, we demonstrated aqueous synthesis of colloidal Cu-doped ZnCdS NCs (d-dots) with pure, color-tunable photoluminescence (PL) in a wide spectral range (from 517 to 650 nm) based on the 'co-nucleation doping' strategy. The influences of the various experimental variables, including Cd/Zn ratio, Cu-doping concentration, pH value and amount of mercaptopropionic acid (MPA), on the optical properties of Cu-doped ZnCdS NCs were systematically investigated. Furthermore, highly efficient and stable dopant emission from Cu:ZnCdS/ZnS core/shell d-dots with PL quantum yield as high as 40% was achieved by the deposition of a ZnS shell around the bare Cu:ZnCdS cores; this is the highest reported to date for aqueous doped NCs. The optical properties and structure of the d-dots were characterized by UV-vis absorption spectra, PL spectra, x-ray photoelectron spectroscopy, powder x-ray diffraction, and transmission electron microscopy. The experimental results indicated that this facile synthesis route would provide a versatile approach for the preparation of other water-soluble sulfide NCs.

High-quality Mn:ZnS doped nanocrystals (d-dots) with photoluminescence (PL) quantum yield (QY) of 50-70% have been synthesized based on nucleation-doping strategy by choosing 1-dodecanethiol (DDT) as the capping ligand. Controlling the growth of small-sized MnS core nanoclusters was successfully achieved by changing the injection temperature of sulfur precursor, the growth time of MnS nuclei, and the amount of DDT. Furthermore, MnS/ZnS core/shell d-dots with a diffusion layer at the interface between the MnS core and the ZnS shell were fabricated through an overcoating of the ZnS shell layer on the presynthesized MnS core nanoclusters. The resulting monodisperse d-dots exhibited spherical shape with a zinc-blende crystal structure. The critical temperature for lattice diffusion of Mn ions in the ZnS host lattice was determined to be about 260 degrees C by annealing the presynthesized and purified Mn:ZnS d-dots.

Water-soluble, highly emissive, color-tunable, and stable Cu:ZnSeS/ZnS core/shell doped nanocrystals (d-dots) with pure dopant emission have been synthesized through a simple aqueous synthetic route. The influence of various experimental variables, including introduction of chloride ions, amount of mercaptopropanoic acid (MPA), pH value and Cu-doping concentration, on the optical properties of Cu dopant emission have been systematically investigated. Through epitaxial growth of a ZnS shell on Cu:ZnSeS cores, the fabricated Cu:ZnSeS/ZnS d-dots exhibit a high PL QY of up to 40%, which is the highest ever reported for any type of water-soluble Cu-doped selenide-based II–VI semiconductor nanocrystals (NCs). Moreover, the serious photostability problem of Cu-based d-dots in the presence of air and light is solved and the quenching of the excitonic emission is suppressed as well. The stable testing of these highly luminescent d-dots shows that the Cu:ZnSeS/ZnS d-dots have better photostability and preserve more than ~90% of the initial intensity in the presence of air and light 30 days later. This new class of green emissive material shows their potential applications in biolabeling, bioimaging, and light emitting devices.