Explore the vast range of titles available.

Replacement of Hg with non-toxic Au based catalysts for industrial hydrochlorination of acetylene to vinyl chloride is urgently required. However Au catalysts suffer from progressive deactivation caused by auto-reduction of Au(I) and Au(III) active sites and irreversible aggregation of Au(0) inactive sites. Here we show from synchrotron X-ray absorption, STEM imaging and DFT modelling that the availability of ceria(110) surface renders Au(0)/Au(I) as active pairs. Thus, Au(0) is directly involved in the catalysis. Owing to the strong mediating properties of Ce(IV)/Ce(III) with one electron complementary redox coupling reactions, the ceria promotion to Au catalysts gives enhanced activity and stability. Total pre-reduction of Au species to inactive Au nanoparticles of Au/CeO 2 &AC when placed in a C 2 H 2 /HCl stream can also rapidly rejuvenate. This is dramatically achieved by re-dispersing the Au particles to Au(0) atoms and oxidising to Au(I) entities, whereas Au/AC does not recover from the deactivation. Despite the extensive efforts to stabilize Au catalysts for industrial hydrochlorination of acetylene to vinyl chloride the deactivation is not overcome yet. Here, the authors demonstrate that the ceria promotion to Au catalysts affords enhanced activity and stability via formation of Au(0)/Au(I) as new active pairs.

The electrocatalytic reduction of CO 2 to CO is slowed by the energy cost of the hydrogenation step that yields adsorbed *COOH intermediate. Here, we report a hydrogen radical (H•)-transfer mechanism that aids this hydrogenation step, enabled by constructing Ni-partnered hetero-diatomic pairs, and thereby greatly enhancing CO 2 -to-CO conversion kinetics. The partner metal to the Ni (denoted as M) catalyzes the Volmer step of the water/proton reduction to generate adsorbed *H, turning to H•, which reduces CO 2 to carboxyl radicals (•COOH). The Ni partner then subsequently adsorbs the •COOH in an exothermic reaction, negating the usual high energy-penalty for the electrochemical hydrogenation of CO 2 . Tuning the H adsorption strength of the M site (with Cd, Pt, or Pd) allows for the optimization of H• formation, culminating in a markedly improved CO 2 reduction rate toward CO production, offering 97.1% faradaic efficiency (FE) in aqueous electrolyte and up to 100.0% FE in an ionic liquid solution. Commercially viable catalytic CO 2 electroreduction to CO would enable many green technologies, yet it is impeded by the initial hydrogenation step of CO 2 . Here, the authors report Ni-Cd dual atom catalysts with complementary properties of favorable adsorption of CO 2 and H to overcome this barrier.

We present a new composite catalyst system of highly defective graphene quantum dots (HDGQDs)-doped 1T/2H-MoS 2 for efficient hydrogen evolution reactions (HER). The high electrocatalytic activity, represented by an overpotential of 136.9 mV and a Tafel slope of 57.1 mV/decade, is due to improved conductivity, a larger number of active sites in 1T-MoS 2 compared to that in 2H-MoS 2 , and additional defects introduced by HDGQDs. High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were used to characterize both the 1T/2H-MoS 2 and GQDs components while Fourier-transform infrared spectroscopy (FTIR) was employed to identify the functional groups on the edge and defect sites in the HDGQDs. The morphology of the composite catalyst was also examined by field emission scanning electron microscopy (FESEM). All experimental data demonstrated that each component contributes unique advantages that synergistically lead to the significantly improved electrocatalytic activity for HER in the composite catalyst system.

Designing high-performance thermal catalysts with stable catalytic sites is an important challenge. Conventional wisdom holds that strong metal-support interactions can benefit the catalyst performance, but there is a knowledge gap in generalizing this effect across different metals. Here, we have successfully developed a generalizable strong metal-support interaction strategy guided by Tammann temperatures of materials, enabling functional oxide encapsulation of transition metal nanocatalysts. As an illustrative example, Co@BaAl 2 O 4 core@shell is synthesized and tracked in real-time through in-situ microscopy and spectroscopy, revealing an unconventional strong metal-support interaction encapsulation mechanism. Notably, Co@BaAl 2 O 4 exhibits exceptional activity relative to previously reported core@shell catalysts, displaying excellent long-term stability during high-temperature chemical reactions and overcoming the durability and reusability limitations of conventional supported catalysts. This pioneering design and widely applicable approach has been validated to guide the encapsulation of various transition metal nanoparticles for environmental tolerance functionalities, offering great potential to advance energy, catalysis, and environmental fields. The authors report a synthetic strategy to create core@shell catalysts using strong metal-support interactions and low-Tammann-temperature compounds. The resulting materials are highly stable and may be useful in industrial applications.

Well dispersible and stable single atom catalysts (SACs) with hydrophilic features are highly desirable for selective hydrogenation reactions in hydrophilic solvents towards important chemicals and pharmaceutical intermediates. A general strategy is reported for the fabrication of hydrophilic SACs by cation‐exchange approach. The cation‐exchange between metal ions (M = Ni, Fe, Co, Cu) and Na+ ions introduced in the skeleton of metal oxide (TiO2 or ZrO2) nanoshells plays the key role in forming M1/TiO2 and M1/ZrO2 SACs, which efficiently prevents the aggregation of the exchanged metal ions. The as‐obtained SACs are highly dispersible and stable in hydrophilic solvents including alcohol and water, which greatly facilitates the catalysis reaction in alcohol. The Ni1/TiO2 SACs have been successfully utilized as catalysts for the selective C=C hydrogenation of cinnamaldehyde to produce phenylpropanal with 98% conversion, over 90% selectivity, good recyclability, and a turnover frequency (TOF) of 102 h−1, overwhelming most reported catalysts including noble metal catalysts. A universal “cation‐exchange” strategy has been presented for the preparation of single‐atom catalysts (SACs) on various metal oxides with hydrophilic features. The Ni1/TiO2 SACs have demonstrated excellent catalytic performance for the selective hydrogenation of C=C in cinnamaldehyde to produce phenylpropanal in isopropanol, with high conversion and selectivity, good recyclability, and a turnover frequency (TOF) of up to 102 h−1.

The development of a safe and affordable redox flow battery technology is important for storing intermittent renewable energy. Here, we design a stable aqueous organic iron-cerium redox flow battery based on the inexpensive metal iron and the abundant rare earth metal cerium, enabled by the universal complexing agent diethylenetriamine pentaacetic acid. Molecular dynamics simulations are employed to screen for carboxyl-containing ligands with different electron donating capacities, revealing that diethylenetriamine pentaacetic acid is an effective candidate to chelate iron and cerium in the negolyte and posolyte, respectively, as verified by experimental characterization. The complexing agent enhances the redox characteristics of iron and cerium and reduces osmotic water migration between the negative and positive chambers by allowing the same ligand in both electrolytes. Our iron-cerium redox flow battery achieves an energy efficiency of 87.7% at 40 mA cm −2 and 80.6% at 100 mA cm −2 , while retaining 95.3% of its initial capacity and maintaining around 86.3% energy efficiency after 500 cycles under neutral environments (100% of state-of-charge). The capacity is still preserved after 1779 cycles even when cycled at high-rates (80 mA·cm −2 , 70% of state-of-charge). Efficient and durable energy storage is vital for renewable integration. Here, the authors design an aqueous iron-cerium redox flow battery using a universal complexing agent that enhances stability and efficiency, achieving long cycle life and high performance in neutral conditions.

We report an unconventional effect of synchrotron X-ray irradiation in which Co–O bonds in thermally annealed (Y, Co)-codoped CeO 2 nanocrystal samples were formed due to, instead of broken by, X-ray irradiation. Our experimental data indicate that escaping oxygen atoms from X-ray-broken Ce–O bonds may be captured by Co dopant atoms to form additional Co–O bonds. Consequently, the Co dopant atoms were pumped by X-rays from the energetically-favored thermally-stable Co-O4 square-planar structure to the metastable octahedral Co-O6 environment, practically a reversal of thermal annealing effects in (Y, Co)-codoped CeO 2 nanocrystals. The band gap of doped CeO 2 with Co dopant in the Co-O6 structure was previously found to be 1.61 eV higher than that with Co in the Co-O4 environment. Therefore, X-ray irradiation can work with thermal annealing in opposing directions to fine tune and optimize the band gap of the material for specific technological applications.

Single‐atom catalysts (SACs), featuring highly uniform active sites, tunable coordination environments, and synergistic effects with support, have emerged as one of the most efficient catalysts for various reactions, particularly for electrochemical CO2 reduction (ECR). However, the scalability of SACs is restricted due to the limited choice of available support and problems that emerge when preparing SACs by thermal deposition. Here, an in situ reconstruction method for preparing SACs is developed with a variety of atomic sites, including nickel, cadmium, cobalt, and magnesium. Driven by electricity, different oxygen‐containing metal precursors, such as MOF‐74 and metal oxides, are directly atomized onto nitrogen‐doped carbon (NC) supports, yielding SACs with variable metal active sites and coordination structures. The electrochemical force facilitates the in situ generation of bonds between the metal and the supports without the need for additional complex steps. A series of MNxOy (M denotes metal) SACs on NC have been synthesized and utilized for ECR. Among these, NiNxOy SACs using Ni‐MOF‐74 as a metal precursor exhibit excellent ECR performance. This universal and general SAC synthesis strategy at room temperature is simpler than most reported synthesis methods to date, providing practical guidance for the design of the next generation of high‐performance SACs. A simple and versatile ambient condition method capable of accommodating a wide range of metals and supports for single‐atom catalyst preparation via operando bond formation driven by electricity is reported. The as‐obtained Ni single atoms using Ni‐MOF‐74 as a precursor exhibit remarkable activity for electrocatalytic CO2 reduction to yield CO.

We report the experimental observation of and theoretical explanation for the reduction of dopant ions and enhancement of magnetic properties in Ce-doped TiO 2 diluted magnetic semiconductors from UV-light irradiation. Substantial increase in Ce 3+ concentration and creation of oxygen vacancy defects in the sample due to UV-light irradiation was observed by X-ray and optical methods. Magnetic measurements demonstrate a combination of paramagnetism and ferromagnetism up to room temperatures in all samples. The magnetization of both paramagnetic and ferromagnetic components was observed to be dramatically enhanced in the irradiated sample. First-principle theoretical calculations show that valence holes created by UV irradiation can substantially lower the formation energy of oxygen vacancies. While the electron spin densities for defect states near oxygen vacancies in pure TiO 2 are in antiferromagnetic orientation, they are in ferromagnetic orientations in Ce-doped TiO 2 . Therefore, the ferromagnetically-oriented spin densities near oxygen vacancies created by UV irradiation are the most probable cause for the experimentally observed enhancement of magnetism in the irradiated Ce-doped TiO 2 .

Ultraviolet (UV) light irradiation on CeO 2 nanocrystals catalysts has been observed to largely increase the material’s catalytic activity and reactive surface area. As revealed by x-ray absorption near edge structure (XANES) analysis, the concentration of subvalent Ce 3+ ions in the irradiated ceria samples progressively increases with the UV-light exposure time. The increase of Ce 3+ concentration as a result of UV irradiation was also confirmed by the UV-vis diffuse reflectance and photoluminescence spectra that indicate substantially increased concentration of oxygen vacancy defects in irradiated samples. First-principle formation-energy calculation for oxygen vacancy defects revealed a valence-hole-dominated mechanism for the irradiation-induced reduction of CeO 2 consistent with the experimental results. Based on a Mars-van Krevelen mechanism for ceria catalyzed oxidation processes, as the Ce 3+ concentration is increased by UV-light irradiation, an increased number of reactive oxygen atoms will be captured from gas-phase O 2 by the surface Ce 3+ ions, and therefore leads to the observed catalytic activity enhancement. The unique annealing-free defect engineering method using UV-light irradiation provides an ultraconvenient approach for activity improvement in nanocrystal ceria for a wide variety of catalytic applications.