Abstract The current industrial ammonia synthesis relies on Haber–Bosch process that is initiated by the dissociative mechanism, in which the adsorbed N 2 dissociates directly, and thus is limited by ...Brønsted–Evans–Polanyi (BEP) relation. Here we propose a new strategy that an anchored Fe 3 cluster on the θ-Al 2 O 3 (010) surface as a heterogeneous catalyst for ammonia synthesis from first-principles theoretical study and microkinetic analysis. We have studied the whole catalytic mechanism for conversion of N 2 to NH 3 on Fe 3 /θ-Al 2 O 3 (010), and find that an associative mechanism, in which the adsorbed N 2 is first hydrogenated to NNH, dominates over the dissociative mechanism, which we attribute to the large spin polarization, low oxidation state of iron, and multi-step redox capability of Fe 3 cluster. The associative mechanism liberates the turnover frequency (TOF) for ammonia production from the limitation due to the BEP relation, and the calculated TOF on Fe 3 /θ-Al 2 O 3 (010) is comparable to Ru B5 site.
Porous CoFe2O4/C NRAs supported on nickel foam@NC (denoted as NF@NC‐CoFe2O4/C NRAs) are directly fabricated by the carbonization of bimetal–organic framework NRAs grown on NF@poly‐aniline(PANI), and ...they exhibit high electrocatalytic activity, low overpotential, and high stability for the oxygen evolution reaction in alkaline media.
Rational design and synthesis of highly active and robust bifunctional non‐noble electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required ...for efficient rechargeable metal–air batteries. Herein, abundant MnO/Co heterointerfaces are engineered in porous graphitic carbon (MnO/Co/PGC) polyhedrons via a facile hydrothermal‐calcination route with a bimetal–organic framework as the precursor. The in situ generated Co nanocrystals not only create well‐defined heterointerfaces with high conductivity to overcome the poor OER activity but also promote the formation of robust graphitic carbon. Owing to the desired composition and formation of the heterostructures, the resulting MnO/Co/PGC exhibits superior activity and stability toward both OER and ORR, which makes it an efficient air cathode for the rechargeable Zn–air battery. Importantly, the homemade Zn–air battery is able to deliver excellent performance including a peak power density of 172 mW cm−2 and a specific capacity of 872 mAh g−1, as well as excellent cycling stability (350 cycles), outperforming commercial mixed Pt/C||RuO2 catalysts. This work highlights the synergy from heterointerfaces in oxygen electrocatalysis, thus providing a promising approach for advanced metal–air cathode materials.
Interface engineering of MnO and Co in porous graphitic carbon (MnO/Co/PGC) polyhedrons is realized by a one‐step pyrolysis of bimetal–organic frameworks. Owing to the active heterointerfaces and robust graphitic carbon, the MnO/Co/PGC exhibits extraordinary activity and stability toward both OER and ORR, making it a promising air cathode for efficient metal–air batteries.
Electrochemical reduction of CO2 could mitigate environmental problems originating from CO2 emission. Although grain boundaries (GBs) have been tailored to tune binding energies of reaction ...intermediates and consequently accelerate the CO2 reduction reaction (CO2RR), it is challenging to exclusively clarify the correlation between GBs and enhanced reactivity in nanostructured materials with small dimension (<10 nm). Now, sub‐2 nm SnO2 quantum wires (QWs) composed of individual quantum dots (QDs) and numerous GBs on the surface were synthesized and examined for CO2RR toward HCOOH formation. In contrast to SnO2 nanoparticles (NPs) with a larger electrochemically active surface area (ECSA), the ultrathin SnO2 QWs with exposed GBs show enhanced current density (j), an improved Faradaic efficiency (FE) of over 80 % for HCOOH and ca. 90 % for C1 products as well as energy efficiency (EE) of over 50 % in a wide potential window; maximum values of FE (87.3 %) and EE (52.7 %) are achieved.
Ultrathin sub‐2 nm SnO2 quantum wires (QWs) composed of individual quantum dots with grain boundaries (GBs) being terminated on the surface were synthesized and examined for CO2 electrochemical reduction toward HCOOH formation. The ultrathin SnO2 QWs deliver higher current densities and remarkably higher Faraday efficiencies of HCOOH in a wide potential window as compared to SnO2 nanoparticles without exposed GBs.
Bi2O3 nanosheets were grown on a conductive multiple channel carbon matrix (MCCM) for CO2RR. The obtained electrocatalyst shows a desirable partial current density of ca. 17.7 mA cm−2 at a moderate ...overpotential, and it is highly selective towards HCOOH formation with Faradaic efficiency approaching 90 % in a wide potential window and its maximum value of 93.8 % at −1.256 V. It also exhibits a maximum energy efficiency of 55.3 % at an overpotential of 0.846 V and long‐term stability of 12 h with negligible degradation. The superior performance is attributed to the synergistic contribution of the interwoven MCCM and the hierarchical Bi2O3 nanosheets, where the MCCM provides an accelerated electron transfer, increased CO2 adsorption, and a high ratio of pyrrolic‐N and pyridinic‐N, while ultrathin Bi2O3 nanosheets offer abundant active sites, lowered contact resistance and work function as well as a shortened diffusion pathway for electrolyte.
Ultrathin Bi2O3 nanosheets have been successfully grown on a conductive multi‐channel carbon matrix (Bi2O3NSs@MCCM). The obtained Bi2O3NSs@MCCM electrocatalyst achieves a comparably high current density at a moderate overpotential for electrochemical CO2 reduction to HCOOH with high selectivity and good long‐term stability.
PdCo nanotube arrays (NTAs) supported on carbon fiber cloth (CFC) (PdCo NTAs/CFC) are presented as high‐performance flexible electrocatalysts for ethanol oxidation. The fabricated flexible PdCo ...NTAs/CFC exhibits significantly improved electrocatalytic activity and durability compared with Pd NTAs/CFC and commercial Pd/C catalysts. Most importantly, the PdCo NTAs/CFC shows excellent flexibility and the high electrocatalytic performance remains almost constant under the different distorted states, such as normal, bending, and twisting states. This work shows the first example of Pd‐based alloy NTAs supported on CFC as high‐performance flexible electrocatalysts for ethanol oxidation.
PdCo nanotube arrays supported on carbon fiber cloth for use as high‐performance electrocatalysts were synthesized for ethanol electrooxidation. The system of nanotube arrays on carbon fiber cloth is highly flexible, and its high electrocatalytic performance is almost constant regardless of the distorted state, such as normal, bent, and twisted.
Display omitted
The research for highly efficient and stable electrocatalysts in fuel cells has attracted substantial interest. Herein, bimetallic alloyed Pt71Co29 lamellar nanoflowers (LNFs) with ...abundant active sites were obtained by a one-pot solvothermal method, where cetyltrimethylammonium chloride (CTAC) and 1-nitroso-2-naphthol (1-N-2-N) served as co-structure-directors, while oleylamine (OAm) as the solvent and reducing agent. The fabricated Pt71Co29 LNFs exhibited the higher mass activity (MA, 128.29 mA mg−1) for oxygen reduction reaction (ORR) than those of home-made Pt48Co52 nanodendrites (NDs), Pt79Co21 NDs and commercial Pt black with the values of 39.46, 49.42 and 22.91 mA mg−1, respectively. Meanwhile, the MA (666.23 mA mg−1) and specific activity (SA, 2.51 mA cm−2) of the constructed Pt71Co29 LNFs for methanol oxidation reaction (MOR) are superior than those of Pt48Co52 NDs (213.91 mA mg−1, 1.99 mA cm−2), Pt79Co21 NDs (210.09 mA mg−1, 1.12 mA cm−2) and Pt black (57.03 mA mg−1, 0.25 mA cm−2). Also, the Pt71Co29 LNFs catalyst exhibited the best durable ability relative to the references. This work demonstrates that the developed strategy provides a facile platform for synthesis of high-performance, low-cost and robust catalysts in practical catalysis, energy storage and conversion.
Solar‐driven transfer hydrogenation of unsaturated bonds has received considerable attention in the research area of sustainable organic synthesis; however, water, the ultimate green source of ...hydrogen, has rarely been investigated due to the high barrier associated with splitting of water molecules. We report a carbon‐nitride‐supported palladium single‐atom heterogeneous catalyst with unparalleled performance in photocatalytic water‐donating transfer hydrogenation compared to its nanoparticle counterparts. Isotopic‐labeling experiments and operando nuclear magnetic resonance measurements confirm the direct hydrogenation mechanism using in situ‐generated protons from water splitting under visible‐light irradiation. Density functional theory calculations attribute the high activity to lower barriers for hydrogenation, facilitated desorption of ethylbenzene, and facile hydrogen replenishment from water on the atomic palladium sites.
Photocatalytic water‐donating transfer hydrogenation can be achieved over a palladium single‐atom catalyst supported on mesoporous carbon nitride, in which hydrogen protons generated from photocatalytic water splitting are sequentially added to various unsaturated bonds. In‐depth characterization confirms the direct hydrogenation mechanism and links the outstanding performance to reduced barriers for hydrogenation and accelerated proton supply from water.
Semiconductor photocatalysts are hardly employed for overall water splitting beyond 700 nm, which is due to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts ...are known to overcome this limitation through interband transitions for creating electron–hole pairs; however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Black tungsten nitride is now employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red‐light irradiation for tungsten nitride. This work represents the first red‐light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization.
Black tungsten nitride can be employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red‐light irradiation for tungsten nitride. CB=conduction band.
The electron-phonon coupling (EPC) in a material is at the frontier of the fundamental research, underlying many quantum behaviors. van der Waals heterostructures (vdWHs) provide an ideal platform to ...reveal the intrinsic interaction between their electrons and phonons. In particular, the flexible van der Waals stacking of different atomic crystals leads to multiple opportunities to engineer the interlayer phonon modes for EPC. Here, in hBN/WS
vdWH, we report the strong cross-dimensional coupling between the layer-breathing phonons well extended over tens to hundreds of layer thick vdWH and the electrons localized within the few-layer WS
constituent. The strength of such cross-dimensional EPC can be well reproduced by a microscopic picture through the mediation by the interfacial coupling and also the interlayer bond polarizability model in vdWHs. The study on cross-dimensional EPC paves the way to manipulate the interaction between electrons and phonons in various vdWHs by interfacial engineering for possible interesting physical phenomena.
PDF
