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Nickel‐iron based hydr(oxy)oxides have been well recognized as one of the best oxygen‐evolving catalysts in alkaline water electrolysis. A crucial problem, however, is that iron leakage during prolonged operation would lead to the oxygen evolution reaction (OER) deactivation over time, especially under large current densities. Here, the NiFe‐based Prussian blue analogue (PBA) is designed as a structure‐flexible precursor for navigating an electrochemical self‐reconstruction (ECSR) with Fe cation compensation to fabricate a highly active hydr(oxy)oxide (NiFeOxHy) catalyst stabilized with NiFe synergic active sites. The generated NiFeOxHy catalyst exhibits the low overpotentials of 302 and 313 mV required to afford large current densities of 500 and 1000 mA cm−2, respectively. Moreover, its robust stability over 500 h at 500 mA cm−2 stands out among the NiFe‐based OER catalysts reported previously. Various in/ex situ studies indicate that the Fe fixation by dynamic reconstruction process can reinforce the Fe‐activated effect on the OER amenable to the industrial‐level large current conditions against the Fe leakage. This work opens up a feasible strategy to design highly active and durable catalysts via thermodynamically self‐adaptive reconstruction engineering. [ABSTRACT FROM AUTHOR]

A robust and highly active homogeneous chiral nickel–phosphine complex for the asymmetric hydrogenation of aliphatic γ‐ and δ‐ketoacids has been discovered. The hydrogenation could proceed smoothly in the presence of 0.0133 mol% catalyst loading (S/C=7500). The coordination chemistry and catalytic behavior of Ni(OTf)2 with (S,S)‐Ph‐BPE were explored by 1H NMR and HRMS. The mechanistic studies revealed that a proton promoted the activation of the substrate C=O bond and controlled the stereoselectivity through hydrogen bonds. A series of chiral γ‐ and δ‐alkyl substituted lactones were obtained in high yields with excellent enantioselectivities (up to 98 % yield and 99 % ee). In addition, this catalytic system also demonstrated that levulinic acid produced from a biomass feedstock was converted into chiral γ‐valerolactone without loss of ee value. [ABSTRACT FROM AUTHOR]

A robust and highly active homogeneous chiral nickel–phosphine complex for the asymmetric hydrogenation of aliphatic γ‐ and δ‐ketoacids has been discovered. The hydrogenation could proceed smoothly in the presence of 0.0133 mol% catalyst loading (S/C=7500). The coordination chemistry and catalytic behavior of Ni(OTf)2 with (S,S)‐Ph‐BPE were explored by 1H NMR and HRMS. The mechanistic studies revealed that a proton promoted the activation of the substrate C=O bond and controlled the stereoselectivity through hydrogen bonds. A series of chiral γ‐ and δ‐alkyl substituted lactones were obtained in high yields with excellent enantioselectivities (up to 98 % yield and 99 % ee). In addition, this catalytic system also demonstrated that levulinic acid produced from a biomass feedstock was converted into chiral γ‐valerolactone without loss of ee value. [ABSTRACT FROM AUTHOR]

CeO2 nanorods (CeO2-nrs), CeO2 nanocubes (CeO2-ncs) and CeO2 nanopolyhedrons (CeO2-nps) were prepared by hydrothermal method and then NiO crystallites were deposited on these supports by precipitation-deposition, respectively. The physic-chemical properties of Ni/CeO2 catalysts were characterized and performances for carbon dioxide methanation reaction were tested. The Ni/CeO2-nrs sample shows well metal dispersion and high concentration of oxygen vacancy, which leads to the high catalytic activity for CO2 methanation. Especially at 300 °C, the CO2 conversion could reach 60%. Further analysis reveals that the content of oxygen vacancy has a positive correlation with the surface area of catalyst. The largest surface area results in the most of oxygen vacancy on the Ni/CeO2-nrs catalyst, and then a large amount of CO2 could be activated at low temperatures. Meanwhile, large surface area facilitates the dispersion of active metals, and improves the degree of H2 activation. The combined effect results in the promotion of catalytic activity for CO2 methanation at low temperatures. CeO2 nanorods (CeO2-nrs), CeO2 nanocubes (CeO2-ncs) and CeO2 nanopolyhedrons (CeO2-nps) supported Ni catalysts were prepared. These catalysts ware tested for CO2 methanation and further characterized by BET, XPS, TEM, H2-TPR and TPD. The results showed that the content of oxygen vacancy has positive correlation with the specific surface area of catalyst. [ABSTRACT FROM AUTHOR]

Deep insight into electrochemical reconstruction aids in the decoding of electrocatalytic mechanisms and the development of design principles for advanced catalysts. Despite recent achievements, research concerning cathodic reconstruction is still lacking compared to the anodic variety. This work captures the electroreductive reconstruction dynamics over bimetal Ni–Mo sulfide by various in/ex situ techniques, and whereby cathodic reconstruction is steered with ion regulation to achieve a heterogeneous Ni–Mo–Fe ternary metal hydroxysulfide (NMFSOH) as a robust hydrogen‐evolving catalyst that is competent in industrial‐level water electrolysis. The thermodynamically adaptive heterosynergism in the resultant NMFSOH catalyst can coordinate water dissociation and hydrogenation for the alkaline hydrogen evolution reaction even at high current densities. A flow‐type alkaline water electrolyzer with dual NMFSOH electrodes affords an electricity consumption of 3.99 kW h Nm−3 and an electricity‐to‐hydrogen efficiency of 88.7%, manifesting its competitive cost‐effectiveness toward practical applications. This study showcases ion‐regulatory reconstruction as an effective strategy to construct high‐performance electrocatalysts. [ABSTRACT FROM AUTHOR]

Thermocatalytic decomposition of methane is proposed to be an economical and green method to produce CO x -free hydrogen and carbon nanomaterials. In this work, the catalytic performance of Ni–Mn–Ru/Al 2 O 3 catalyst under different reaction parameters (such as, pre-reduction temperature, reaction temperature, space velocity, etc.) were investigated to obtain optimum reaction conditions. The catalysts were characterized by N 2 adsorption/desorption, X-ray diffraction, inductively coupled plasma optical emission spectrometer and hydrogen temperature programmed reduction. For the 60 wt% Ni-5 wt% Mn-10 wt% Ru/Al 2 O 3 catalyst using Ru(NO)(NO 3) x (OH) y (x + y = 3) as Ru precursor, the methane conversion rate obtained is high as 93.76% under optimum reaction conditions (reduction at 700 °C for 1 h, reaction at 750 °C, GSHV = 36,000 mL/g cat h). Carbon nanomaterials formed during the process of methane thermocatalytic decomposition were characterized by scanning electron microscopy, thermal gravimetric analyzer and Raman spectroscopy. Carbon nanofibers were formed over all the Ni–Mn–Ru/Al 2 O 3 catalysts. • Performance of Ni–Mn–Ru/Al 2 O 3 catalyst for TCD of CH 4 was studied. • The CH 4 conversion rate was 93.76% under optimum reaction conditions. • Carbon nanofibers were formed on all Ni–Mn–Ru/Al 2 O 3 catalysts. [ABSTRACT FROM AUTHOR]

Catalyst samples for CH 4 decomposition were prepared from red mud (RM) by an acid-leaching neutralization precipitation approach. Water-washing the resultant precipitates multiple times, followed by drying at 105 °C and calcination at 500 °C, resulted in a threshold of residual Na 2 O, equivalent to 96% Na 2 O removal. Drying the precipitate at a higher temperature of 200 °C, followed by repeated water washing, provided a deeper Na 2 O removal of 99% and made the resultant samples more active for the targeted reaction. Subsequently, four catalyst samples with a simulated red mud composition and NaOH contents from 0 to 0.3 wt% were prepared and the catalytic test results revealed that the Na 2 O remaining in the RM-derived catalysts did not only inhibit their activation in CH 4 but also lower their maximal activities for CH 4 decomposition. Finally, two catalysts with the same simulated red mud composition and their Na impregnated respectively on Fe 2 O 3 and a mixture support of Al 2 O 3 -SiO 2 -TiO 2 were prepared and tested to explore the effect of Na distribution on the activation behavior of RM-derived catalysts for CH 4 decomposition. The activity testing results showed that it was the Na residual dispersed on iron oxides in the RM-derived samples to significantly inhibit the activation of CH 4 decomposition. • Na 2 O in the RM-derived catalysts inhibited the activities for CH 4 decomposition. • An approach was provided to realize the deeper Na 2 O removal of 99% in Red Mud. • The Na dispersed on Fe 2 O 3 played an inhibiting role in the activation of catalysts. [ABSTRACT FROM AUTHOR]

Here, we report an inexpensive nickel-phosphine complex that can catalyse neat levulinic acid (LA) to γ-valerolactone (GVL) without additive at 1 atm H2, and the catalyst can be reduced to 0.01 mol% at 30 atm. 5.8 kg LA was successfully converted to GVL in a yield of 94% with 0.1 mol% catalyst. DFT calculations and in situ APXPS indicate that L–Ni+–H species are the key active intermediates. [ABSTRACT FROM AUTHOR]

Chiral conjugated microporous polymers (CCMPs) containing amide groups were designed and synthesized by Sonogashira coupling polymerization. CCMPs are reported for the first time as heterogeneous asymmetric catalyst platforms for the stabilization of Pd with applications in asymmetric catalytic synthesis. Four Pd/CCMPs heterogeneous catalysts exhibited efficient catalytic activity (of up to 87% yield) and excellent enantioselectivity (of up to 97% enantiomeric excess value) in the asymmetric Henry reaction, with a wide range of substrates and easy recovery. The Pd/CCMPs composites could be easily recycled and maintained catalytic activity after 3 cycles of reactions. A rational catalytic cycle was proposed to further understand the role of Pd/CCMPs in the Henry reaction. This study greatly extends the application of CCMPs in heterogeneous asymmetric catalysis. [Display omitted] • Functionalized chiral conjugated microporous polymers (CCMPs) were synthesized. • The Pd/CCMPs are reported for the first time as heterogeneous asymmetric catalysts. • The Pd/CCMPs composites show efficient catalytic activity and enantioselectivity. • The prepared Pd/CCMPs composites showed a wide range of substrates and reusability. [ABSTRACT FROM AUTHOR]

High-density single-crystalline TiO 2 nanowires are successfully fabricated on a TiSi 2 layer using a new self-induced catalyst-free method by APCVD. The results show that the high aspect ratio nanowires with diameters of 20–50 nm and lengths of about 3 μm are obtained on a TiSi 2 layer at 720 °C. The length of TiO 2 nanowires increases with the preparation time until Ti is exhausted. The nanowires shape changes with the concentration of O 2 and temperature. When the temperature is above 720 °C or the flux of O 2 is over 6 sccm, the density and length of nanowires decrease under the combined effect of the increasing lateral surface diffusion and longitudinal growth. The formation of TiO 2 nanowires comes along with the consumption of TiSi 2 , TiO 2 nanowires grow along the [001] direction of the tetragonal rutile TiO 2 crystal from the bottom, with the tip being pushed upwards. The growth process is proposed which is consistent with our experiment results. [ABSTRACT FROM AUTHOR]

Reforming methane to produce syngas is a subject that generates considerable interest. The process requires catalysts that possess high-performance active sites to activate stable C–H bonds. Herein, we report a facile synthetic strategy to prepare Ni-based catalysts by complexation–impregnation (Ni-G/SiO2-C) and precipitation–impregnation (Ni-G/SiO2-P) methods using glycine as a complexing agent. The particle size of Ni in both types of catalysts is decreased by adding glycine in the preparation process. Nevertheless, the preparation methods and amount of glycine play a significant role in the particle size and distribution of Ni over the Ni-based catalysts. The smaller particle size and narrower distribution of Ni were obtained in the Ni-G/SiO2-P catalyst. The catalysts were comparatively tested for carbon-dioxide reforming of methane (CDR). Ni-G/SiO2-P showed better CDR performance than Ni-G/SiO2-C and Ni/SiO2 and increased stability because of the smaller particle size and narrower distribution of Ni. Moreover, a high-performance Ni-based catalyst was prepared by optimizing the amount of glycine added. An unobservable deactivation was obtained over Ni-G-2/SiO2-P and Ni-G-3/SiO2-P for CDR during TOS = 20 h. Thus, a new promising method is described for the preparation of Ni-based catalysts for CDR. [ABSTRACT FROM AUTHOR]