The development of efficient catalysts for the selective hydrogenation of dimethyl oxalate (DMO) to high-value oxygenates is of great industrial importance. This study presents a systematic investigation into the promotional effect of gallium (Ga) on Cu/SiO2 catalysts for tailoring product selectivity in DMO hydrogenation. A series of GaxCu30/SiO2 catalysts with varying Ga loadings (x = 0.5, 1, 3 wt%) were synthesized via the ammonia evaporation method. With a moderate Ga doping of 0.5 wt%, the Ga0.5Cu30/SiO2 catalyst achieved an exceptional ethylene glycol (EG) yield of 74 %, which is three times higher than its Ga-free counterpart (23 %). Further increases in Ga loading to 1 and 3 wt% redirected the reaction pathway, steering the selectivity towards ethanol (ET, 81 %) and 2-methoxyethanol (MT, 54 %), respectively. Characterization by N2O titration, XRD, XPS, in situ FT-IR and H2-TPR revealed that Ga incorporation fine-tunes the synergy between metallic Cu0 (for H2 dissociation) and Cu+ sites (for C=O bond polarization). Concurrently, the generated surface acid sites facilitate subsequent dehydration and hydrogenolysis steps. Consequently, the catalytic performance is directly correlated with the evolution of Cu valence states and surface acidity. This work provides a rational strategy for designing multifunctional catalysts for the selective synthesis of target chemicals from DMO.

The selective conversion of syngas to C4+ long-chain alcohols holds significant industrial and scientific interest, but challenges in product selectivity and process efficiency remain. Here, we report a precisely catalytic strategy for C4+ alcohol synthesis with a selectivity of 80% at 17% CO conversion. The reaction channel involves: (i) the development Cs2O-Co2C-Co catalysts, capable of catalyzing CO hydrogenation to long-chain oxygenates/olefins; and (ii) complete conversion to C4+ alcohols is subsequently achieved on the single-Rh-site and Cu-ZrO2 interfaces by integrated cooperative catalysis. A comprehensive catalyst design and compatibility assessment of each catalytic module ensures optimal combinations, meanwhile effectively eliminates costly separation steps, and reduces CO2 selectivity down to 1%. The developed process achieves ultra-high carbon-efficiency (>95%) and improves oxygen-efficiency, effectively overcoming the key limitations of current syngas conversion technologies and thus representing a competitive and sustainable solution for producing high-value long-chain alcohols with a minimal carbon footprint.

The direct synthesis of high-value-added long-chain primary alcohols (LPAs, C6+OH) from syngas (CO + H2) is highly attractive. However, low selectivity of targeted products is generally obtained due to competitive dissociative and non-dissociative CO adsorption, as well as uncontrollable chain growth that causes a complex reaction network. Herein, we report that Na-driven Co2C-Co dual active sites could be engineered by loading the Na promoter onto an activated carbon supported Co-based catalyst, achieving total alcohol selectivity of ca. 46% with a remarkable LPAs fraction higher than 65%, which represents the first report of high LPA selectivity in literature. Comprehensive characterizations and experiments indicated that electron-rich state of Co2C-Co sites was generated through Na promotion, which enhances the surface basicity of the catalyst and favors chain propagation. Moreover, Na promotes the dissociation of CO to form *C species, facilitating the transformation of metallic Co into Co2C and leading to the formation of Na-driven Co2C-Co active sites that are closely associated with CO insertion. Density functional theory calculations show that Na significantly also promotes C-C coupling while inhibiting hydrogenation and promoting CO insertion, which is deemed to be the intrinsic mechanism behind the high LPAs selectivity. This work elucidates a dual role of Na in constructing active sites and modulating surface reaction energetics, providing a design paradigm to break the LPAs selectivity barrier in syngas conversion.

Highly effective and stable hydrogenation of dimethyl adipate (DMA) to 1,6-hexanediol (1,6-HDO) over nonnoble metal-based catalysts under relatively mild reaction conditions was quite attractive, yet challenging. Herein, a series of Cu-based catalysts with tunable acid-base sites were developed for the hydrogenation of DMA to 1,6-HDO. Among them, the CuMgAl hydrotalcite-derived Cu-35Mg45AlO catalyst was proven to be the most effective catalyst. Under relatively mild reaction conditions (190 degrees C and 5 MPa), DMA conversion of 99.0% with 1,6-HDO selectivity of 97.6% was achieved. Moreover, negligible deactivation was observed over a long-term (432 h) stability test. Characterization results revealed that the spatial segregation of the hydrotalcite structure and the interaction between Cu species and MgAl2O4 spinel are responsible for the highly dispersed and stable Cu species. The synergistic mechanism of Cu-0, Cu+, and weak acidic sites was proposed to play a crucial role in DMA hydrogenation, and the promotional role of acid and base sites was also disclosed.

Cu-based catalysts are extensively employed in dimethyl oxalate (DMO) hydrogenation, but it is rather challenging to obtain methyl glycolate (MG) over traditional Cu-based catalysts with high selectivity at high DMO conversion. Herein, the physicochemical properties of the typical Cu/SiO2 catalyst and its corresponding catalytic performance toward DMO hydrogenation were tuned by surface modification with a biological template (histidine). On the premise of near-total conversion of DMO, the MG selectivity substantially increased from 15.7 % to 82.9 % when the typical Cu/SiO2 catalyst was modified by 7 wt% histidine, which was fairly impressive among the reported results up to now. Furthermore, comprehensive characterization and kinetic study disclosed the underlying mechanism. After thermal treatment, histidine retains its skeleton framework (imidazole), the emerging Cu-N interaction weakened the Cu-silica interaction, leading to the reduction in percentage of Cu+ and increase in electron density on the Cu/SiO2 catalyst. As a result, the adsorption and activation ability toward MG were obviously suppressed, which was proved as the critical step for selective hydrogenation of DMO toward MG.

Heterogeneous single-metal-site catalysts frequently encounter issues related to the poor stability of their coordination structures, hindering their industrial applications. Synthesizing bimetallic single-metal-site catalysts with two closely connected single sites may realize the full potential of single-site catalysts. Herein, we present a "top-down" dispersion process to prepare bimetallic single-metal-site catalysts from Pd-Ag alloy nanoparticles induced by CO and CH3I mixture, with the unique binuclear complex structure of Pd1-Ag1 established as PdI2(CO)-I2-AgI by combined characterization. The Pd1-Ag1/activated carbon (AC) catalyst showed a three times increase in conversion for acetylene dialkoxycarbonylation compared to Pd1/AC, owing to the promotive effect of the single-Ag-site via the binuclear complex configuration. Moreover, Pd1-Ag1/AC showed 98% selectivity for 1,4-unsaturated dicarboxylic acid esters over ten cycles without apparent decay, with the activated adsorption amount of acetylene doubled and the reduction of active Pd1 & ouml;+ species partially inhibited. According to density functional theory calculations, the Pd1-Ag1/AC catalyst exhibited a substantially lower reaction energy barrier of 0.45 eV for the rate-determining step compared with that of the Pd1/AC catalyst (1.06 eV). This study provides insight into the preparation and synergetic catalysis of bimetallic single-metal-site catalysts. Published by Elsevier B.V. All rights reserved.

In this study, few-layer graphene was directly fabricated on a SiO2/Si substrate through the rapid thermal annealing of Ni films with low carbon content (C:Ni) deposited by reactivedirect current magnetron sputtering (DCMS). XPS, XRD and TEM results confirmed that carbon atoms were doped into the Ni lattice and there are no carbon clusters embedded in the films. The study investigated various parameters and factors affecting graphene preparation, including the carbon content in the Ni film, the thickness of the Ni film, the annealing temperature, the heating rate, and other relevant factors. Raman spectroscopy revealed that few-layer graphene occurs on the surface of the C:Ni film, with I-2D/I-G ratio greater than 1 and I-D/I-G less than 0.2, indicating the excellent quality of the graphene. Raman mapping images confirmed that the monolayer graphene covered approximately 90 % of the 10 x 10 mu m(2) area on the surface. Furthermore, it was observed that the low carbon content of the Ni film facilitated the preparation of few-layer graphene. High temperatures were found to enhance carbon diffusion, which has a great impact on the layer number and quality of graphene. The synthesis of graphene can be attributed to metal-induced crystallization and carbon diffusion mechanisms. The experimental findings are expected to greatly advance the synthesis of graphene and broaden its potential applications in various fields.

Promotional effects of oxygen vacancies of spinel catalysts in CO2 hydrogenation are reported in early works, but the mechanistic origins remain elusive. Here, CoAl2O4 spinels with varying numbers of oxygen vacancies are deliberately designed by a sol-gel method and different post-treatments. By combining catalytic testing, advanced electron microscopic and spectroscopic characterizations, and computational studies, the unusual oxygen vacancy-dependent catalytic behaviors are rationalized. Our work reveals that i) perfect spinel crystals possessing least oxygen vacancies can effectively constrain the Co2+ species at working conditions that are less active but selective to CO; and ii) vacancy-rich spinels promote both H-2 and CO2 activations and COOH* formation, explaining the higher hydrogenation activity, but overwhelming vacancies cause Co2+ reduction and promote direct CO2 * dissociation to CO* and deep hydrogenation to CH4. These molecular-level understandings reinforce the idea of proper design of oxygen vacancies to achieve activity-selectivity balance.

The spin-forbidden O(3P2) + CO(X1Σ+, v) channel formed from the photodissociation of CO2 in the low energy band centered at 148 nm is investigated by using the time-sliced velocity-mapped ion imaging technique. The vibrational-resolved images of the O(3P2) photoproducts measured in the photolysis wavelength range of 144.62-150.45 nm are analyzed to give the total kinetic energy releases (TKER) spectra, CO(X1Σ+) vibrational state distributions, and anisotropy parameters (β). The TKER spectra reveal the formation of correlated CO(X1Σ+) with well resolved v = 0-10 (or 11) vibrational bands. Several high vibrational bands that were observed in the low TKER region for each studied photolysis wavelength exhibit a bimodal structure. The CO(X1Σ+, v) vibrational distributions all present inverted characteristics, and the most populated vibrational state changes from a low vibrational state to a relatively higher vibrational state with a change in the photolysis wavelength from 150.45 to 144.62 nm. However, the vibrational-state specific β-values for different photolysis wavelengths present a similar variation trend. The measured β-values show a significant bulge at the higher vibrational levels, in addition to the overall slow decreasing trend. The observed bimodal structures with mutational β-values for the high vibrational excited state CO(1Σ+) photoproducts suggest the existence of more than one nonadiabatic pathway with different anisotropies in the formation of O(3P2) + CO(X1Σ+, v) photoproducts across the low energy band.

Understanding vacuum ultraviolet photodissociation dynamics of Carbonyl sulfide (OCS) is of considerable importance in the study of atmospheric chemistry. Yet, photodissociation dynamics of the CS(X1Σ+) + O(3Pj=2,1,0) channels following excitation to the 21Σ+(ν1',1,0) state has not been clearly understood so far. Here, we investigate the O(3Pj=2,1,0) elimination dissociation processes in the resonance-state selective photodissociation of OCS between 147.24 and 156.48 nm by using the time-sliced velocity-mapped ion imaging technique. The total kinetic energy release spectra are found to exhibit highly structured profiles, indicative of the formation of a broad range of vibrational states of CS(1Σ+). The fitted CS(1Σ+) vibrational state distributions differ for the three 3Pj spin-orbit states, but a general trend of the inverted characteristics is observed. Additionally, the wavelength-dependent behaviors are also observed in the vibrational populations for CS(1Σ+, v). The CS(X1Σ+, v = 0) has a significantly strong population at several shorter wavelengths, and the most populated CS(X1Σ+, v) is gradually transferred to a higher vibrational state with the decrease in the photolysis wavelength. The measured overall β-values for the three 3Pj spin-orbit channels slightly increase and then abruptly decrease as the photolysis wavelength increases, while the vibrational dependences of β-values show an irregularly decreasing trend with increasing CS(1Σ+) vibrational excitation at all studied photolysis wavelengths. The comparison of the experimental observations for this titled channel and the S(3Pj) channel reveals that two different intersystem crossing mechanisms may be involved in the formation of the CS(X1Σ+) + O(3Pj=2,1,0) photoproducts via the 21Σ+ state.

Tactile technologies that can identify human body features are valuable in clinical diagnosis and human-machine interactions. Previously, cutting-edge tactile platforms have been able to identify structured non-living objects; however, identification of human body features remains challenging mainly because of the irregular contour and heterogeneous spatial distribution of softness. Here, freestanding and scalable tactile platforms of force-softness bimodal sensor arrays are developed, enabling tactile gloves to identify body features using machine-learning methods. The bimodal sensors are engineered by adding a protrusion on a piezoresistive pressure sensor, endowing the resistance signals with combined information of pressure and the softness of samples. The simple design enables 112 bimodal sensors to be integrated into a thin, conformal, and stretchable tactile glove, allowing the tactile information to be digitalized while hand skills are performed on the human body. The tactile glove shows high accuracy (98%) in identifying four body features of a real person, and four organ models (healthy and pathological) inside an abdominal simulator, demonstrating identification of body features of the bimodal tactile platforms and showing their potential use in future healthcare and robotics.

Vacuum ultraviolet photodissociation dynamics of N2O+h nu -> N-2(X-1 Sigma(+)(g))+O(S-1(0)) in the short wavelength tail of D-1 Sigma(+) band has been investigated using the time-sliced velocity-mapped ion imaging technique by probing the images of the O(S-1(0)) photoproducts at a set of photolysis wavelengths including 121.47 nm, 122.17 nm, 123.25 nm and 123.95 nm. The product total kinetic energy release distributions, vibrational state distributions of the N-2(X-1 Sigma(+)(g)) photofragments and angular anisotropy parameters have been obtained by analyzing the raw O(S-1(0)) images. It is noted that additional vibrationally excited photoproducts (3 <= v <= 8) with a Boltzmann-like feature start to appear except the non-statistical component as the photolysis wavelength decreases to 123.25 nm, and the corresponding populations become more pronounced with decreasing of the photolysis wavelength. Furthermore, the vibrational state specific anisotropy parameter fi at each photolysis wavelength exhibits a drastic fluctuation near beta=1.75 at v<8, and decreases to a minimum as the vibrational quantum number further increases. While the overall anisotropy parameter beta for the N-2(X-1 Sigma(+)(g))+O(S-1(0)) channel presents a roughly monotonical increase from 1.63 at 121.47 nm to 1.95 at 123.95 nm. The experimental observations suggest that there is at least one fast nonadiabatic pathway from initially prepared D-1 Sigma(+) state to the dissociative state with bent geometry dominating to generate the additional vibrational structures at high photoexcitation energies.

The catalytic hydrogenolysis of a typical model compound of mulching film waste, polyethylene, was investi-gated as a potential way to improve economic efficiency of mulching film recycling. Nickel-based heterogeneous catalysts are proposed for polyethylene hydrogenolysis to produce liquid hydrocarbons. Among catalysts sup-ported on various carriers, Ni/SiO2 catalyst shows the highest activity which may due to the interactions between nickel and silica with the formation of nickel phyllosilicate. As high as 81.18% total gasoline and diesel range hydrocarbon was obtained from the polyethylene hydrogenolysis at relatively mild condition of 280 ?, and 3 MPa cold hydrogen pressure. The result is comparable to what have been reported in previous studies using noble metal catalysts. The gasoline and diesel range hydrocarbon are n-alkanes with a distribution at a range of C-4-C-22. The gas products are primarily CH4 along with a small amount of C2H6 and C3H8. High yield of CH4 as much as 9.68% was observed for the cleavage of molecule occurs along the alkane chain.

A continuous flow system based on a micro-packed bed reactor was developed for hydrodechlorination, and the hydrogenation of chlorobenzene was selected as the model reaction. With the optimal reaction conditions, a conversion and selectivity of 100% were obtained.

A P-modified Co/SiO2 catalyst was reported for the first time in the selective hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) reaction and the synthesized Co8P/SiO2 exhibited 94.6% conversion of DMO and 88.1% selectivity to MG during a 300 h continuous test. The doping element of P in the catalyst was indispensable and played an important role in improving the catalytic performance of the Co/SiO2 catalyst.

The photodissociation of OCS is necessary to model the primary photochemical processes of OCS in the global cycling of sulfur and interstellar photochemistry. Here, by combining the time-sliced velocity-map ion imaging technique with the single vacuum ultraviolet photon ionization method, we have studied the CO(1Σ+, v) + S(1D2) photoproduct channel from the OCS photodissociation via the eight different vibrational resonances ( = 1-8) in the 21Σ+(, 1, 0) ← X1Σ+(0, 0, 0) band. From the measured S(1D2) images, the wavelength-dependent CO(1Σ+, v) vibrational state populations have been obtained in the wavelength range of 142.98-154.37 nm. The majority of the CO(1Σ+, v) photoproducts are shown to abruptly populate from low vibrational states to high vibrational states as the photolysis wavelength decreases from 152.38 to 148.92 nm. The anisotropy parameters (β) for the CO(1Σ+, v) + S(1D2) channel have also been determined from the images of the S(1D2) photoproducts. It is found that the vibrational state-specific β-values present a similar decreasing trend with increasing CO vibrational excitation for all the eight vibrational resonances of OCS*(21Σ+). These observations indicate that there is a possibility that more than one non-adiabatic dissociation pathways with different dissociation lifetimes are involved in the formation of CO(1Σ+) + S(1D2) photoproducts from the initial vibronic levels of the 21Σ+ state to the final dissociative state.

Brain–machine interfaces typically rely on electrophysiological signals to interpret and transmit neurological information. In biological systems, however, neurotransmitters are chemical-based interneuron messengers. This mismatch can potentially lead to incorrect interpretation of the transmitted neuron information. Here we report a chemically mediated artificial neuron that can receive and release the neurotransmitter dopamine. The artificial neuron detects dopamine using a carbon-based electrochemical sensor and then processes the sensory signals using a memristor with synaptic plasticity, before stimulating dopamine release through a heat-responsive hydrogel. The system responds to dopamine exocytosis from rat pheochromocytoma cells and also releases dopamine to activate pheochromocytoma cells, forming a chemical communication loop similar to interneurons. To illustrate the potential of this approach, we show that the artificial neuron can trigger the controllable movement of a mouse leg and robotic hand. An artificial neuron that detects dopamine using a carbon-based electrochemical sensor and then processes the sensory signals using a memristor with synaptic plasticity, before stimulating dopamine release via a heat-responsive hydrogel, can be used to trigger the controllable movement of a mouse leg and robotic hand.

A strategy of in situ depositing 2D COFs on heterogeneous catalysts was reported for the first time to suppress the agglomeration and sintering of the supported metal nanoparticles during hydrogenation processes. The COF-decorated nanocatalysts exhibited excellent stability in various hydrogenation reactions including the reduction of dimethyl oxalate (DMO), furfural, and other chemicals.