Cu In Catalyst Research Articles

Promoted stability of Cu/ZnO/Al2O3 catalysts formethanol production from CO2 hydrogenation by La modification

Deactivation of Cu/ZnO/Al2O3 catalysts in CO2 hydrogenation to methanol reaction is one of the main reasons limiting their application. We synthesized a series of La modified Cu/ZnO/Al2O3 catalysts by adding different contents of La to improve the stability. In the 100 h short-term stability test at 200 °C under 3 MPa with a GHSV of 12000 mL/(g·h), the unmodified Cu/ZnO/Al2O3 catalysts degraded obviously over 100 h. In sharp contrast, the stability was significantly promoted by the addition of La. The best activity was achieved with 5% La added samples (4% CO2 conversion and 85% methanol selectivity),which also showed impressive stability over 1000 h except about 17% deactivation during the initial 190−220 h. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results revealed that the addition of 5% La improved the dispersion of Cu and Zn, inhibited the sintering of Cu, stabilized the Cu0/+ species and retarded oxidation of Cu in catalysts, which attributed to the high stability of the catalysts.

Evolution of Cu-In Catalyst Nanoparticles under Hydrogen Plasma Treatment and Silicon Nanowire Growth Conditions.

We report silicon nanowire (SiNW) growth with a novel Cu-In bimetallic catalyst using a plasma-enhanced chemical vapor deposition (PECVD) method. We study the structure of the catalyst nanoparticles (NPs) throughout a two-step process that includes a hydrogen plasma pre-treatment at 200 °C and the SiNW growth itself in a hydrogen-silane plasma at 420 °C. We show that the H2-plasma induces a coalescence of the Cu-rich cores of as-deposited thermally evaporated NPs that does not occur when the same annealing is applied without plasma. The SiNW growth process at 420 °C induces a phase transformation of the catalyst cores to Cu7In3; while a hydrogen plasma treatment at 420 °C without silane can lead to the formation of the Cu11In9 phase. In situ transmission electron microscopy experiments show that the SiNWs synthesis with Cu-In bimetallic catalyst NPs follows an essentially vapor-solid-solid process. By adjusting the catalyst composition, we manage to obtain small-diameter SiNWs-below 10 nm-among which we observe the metastable hexagonal diamond phase of Si, which is predicted to have a direct bandgap.

Modulation of the Coordination Environment of Copper for Stable CO2 Electroreduction with Tunable Selectivity

Manipulating the product selectivity of an electrochemical CO2 reduction reaction (CO2RR) is challenging due to the unclear and uncontrollable active sites. Here, we report stable CO2RR operation with tunable product selectivity over a family of molecule-modulated copper catalysts. The coordination environment of Cu in catalysts is modulated by an imidazole-based molecule via different synthetic routes. Various carbonaceous products ranging from carbon monoxide, methane, and ethylene were selectively produced via, respectively, tuning the coordination environment of copper atoms from Cu-N, Cu-C, and Cu-Cu. Density functional theory (DFT) calculations reveal that the Cu-N sites weaken the adsorption energy of the *CO intermediate, which is beneficial for CO desorption. The Cu-C and Cu-Cu sites, respectively, facilitate the formation of *OCOH and *(CO)2 intermediates, favoring the CH4 and C2H4 pathways. This work provides a stable and simple model system for studying the influence of coordination elements on the product selectivity of CO2RR.

Elucidating the structure evolution and reaction mechanism of the Cu-In bimetallic catalysts during CO2RR

In-based bimetallic catalysts show great potential to reduce CO2 electrochemically. However, the nature of active sites and reaction mechanisms are not fully understood. This study systematically investigates the role of Cu in the Cu-In bimetallic catalysts during the reaction. The partial current densities of formate and CO show a linear correlation with increased Cu content. CuIn3 shows a total current density of 6.40 mA cm−2 and the highest Faradic efficiency for C1 products of 99.3% at −0.7 V vs RHE. A series of characterizations reveal that the Cu1+ species dope into the In(OH)3 lattice for the Cu-In catalysts, while small CuO nanoparticles also form on the surface of catalyst with high Cu contents. The CuO and Cu1+ species are reduced to metallic Cu0, leading to the formation of the Cu0-In(OH)3 interfacial sites. Adding Cu is found to facilitate the adsorption of CO2 and shift the rate-determining step for formate production.

Perforated nitrogen-rich graphene-like carbon nanolayers supported Cu-In catalyst for boosting CO2 electroreduction to CO

The combination of a powerful CO2-enriching carrier and robust active component provides a new idea for the construction of efficient catalysts for electrocatalytic CO2 reduction. Herein, novel perforated nitrogen-rich graphene-like carbon nanolayers (PNGC) are prepared from biomass derivatives, which promotes the oriented deposition of In-doped Cu2(OH)3(NO3) nanosheet patches. A robust Cu-In/PNGC composite catalyst is then obtained via simple in-situ electrochemical reduction. Unsurprisingly, Cu-In/PNGC exhibits a CO Faradaic efficiency (FECO) of 91.3% and a remarkable CO partial current density (jCO) of 136.4 mA cm−2 at a moderate overpotential of 0.59 V for electrocatalytic CO2 reduction reaction (CO2RR). DFT calculations and experimental studies indicate that the strong carrier effect of PNGC makes PNGC carried Cu-In nanosheets improved the adsorption capacity of CO2 gas, reconfigured electronic structure, and reduced free energy of key intermediate formation, thereby the CO2 activation and conversion are promoted.

3D Cu/In nanocones by morphological and interface engineering design in achieving a high current density for electroreduction of CO2 to syngas under elevated pressure

Syngas produced electrochemically from carbon dioxide electroreduction is quite appealing. To develop the process on a large scale, it would be essential to use selective and cheap electrodes, and to get high production rate with low energy consumptions. Cu-In catalysts are one of the most intriguing in this context because of their inexpensive cost, high Faradaic efficiency in CO (FECO), and excellent stability. However, because of the low current densities demonstrated in aqueous electrolytes, productivities have been rather low up to date. This paper shows that the morphological and interface engineering of 3D Cu/In nanocones designed by facile electrodeposition can perform very well for electrochemical carbon dioxide reduction to syngas. Under 1 atm of CO2 pressure and − 0.6 V to − 1.1 V versus RHE, the current density can reach − 20 mA cm−2 with a FE of 100%. Besides, an increase in CO2 pressure as high as 9.5 bars has increased the content of CO2, which enabled CO partial current density (jCO) to achieve −229.88 mA cm−2, a new record in neutral pH electrolyte for most of the Cu-based electrodes. It proves 3D Cu/In NCs could be the most efficient catalyst for CO2RR in syngas production to the best of our knowledge.

Copper-indium hydroxides derived electrocatalysts with tunable compositions for electrochemical CO2 reduction

Bimetallic Cu-In hybrid electrocatalysts are promising noble metal-free catalysts for selective electrochemical CO2 reduction reaction (ECO2RR). Most reports show Cu-In catalysts are selective towards CO evolution. However, few show similarly high selectivity towards formate. Herein we fabricated composition tunable Cu-In hydroxides (CuxIny-OH) by the hydrothermal method and studied their composition effect on electrochemical CO2 reduction in detail. We found that the selectivity of CO2 reduction products shifted from CO to formate when the content of In increased in the CuxIny-OH electrocatalysts. The Cu rich electrocatalyst mostly produced CO, which could achieve a Faradaic efficiency (FE) to 75.8% at −0.59 V vs. RHE (Cu76In24 based electrocatalysts). In comparison, the In rich electrocatalysts selectively produced formate, which possessed the FE of formate up to 85% at −1.01 V vs. RHE. Our work systematically illustrates the composition effect on hybrid catalysts, and provides insights into the design of highly selective catalysts for ECO2RR.

Discovering indium as hydrogen production booster for a Cu/SiO2 catalyst in steam reforming of methanol

We report on the use of In as an effective H2 production promoter in a Cu/SiO2 catalyst for the steam reforming of methanol. To date, In promotion has been limited to noble metals because of its tendency to “bury” other metals thus compromising the catalytic activity. Here, we prepared a silica-supported Cu-In catalyst via a urea-assisted co-precipitation method that showed a higher H2 productivity compared to the monometallic catalyst and a remarkable H2/CO2 molar ratio of almost 3 at 220 °C. Through XPS, XRPD and HRTEM-EDX along with H2- and CO-TPR, H2O-TPD, and N2O titrations, supported by computational modeling, we attributed such superior performances to an easier H2O activation due to improved electronic properties of the Cu phase, that is, its lower oxidation state via electron density transfer from the InOx buffer phase as a 1D “necklace” structures crucially mediating the interaction of small Cu nanoparticles (2.6 nm) and silica.

Catalytic hydrogenolysis of lignin in ethanol/isopropanol over an activated carbon supported nickel-copper catalyst

Lignin is the renewable and abundant source of aromatics on earth, and the depolymerization of lignin provides significant potential for producing valuable monophenols. In this work, catalytic hydrogenolysis of organosolv poplar lignin (OPL) in ethanol/isopropanol solvent over monometallic and bimetallic nonprecious catalysts was investigated. Ni/C and a series of NiCu/C catalyst with different Cu loadings were prepared and applied for depolymerization of OPL. The highest yield of phenolic monomers was 63.4 wt% achieved over the Ni10Cu5/C catalyst at 270 °C without external H2. The introduction of Cu in catalysts further promoted the hydrogen donor process of ethanol/isopropanol solvent and facilitated the cleavage of lignin linkages, resulting in the decreased molecular weight of bio-oil. The possible lignin dimer type structures, such as diphenylethane (β-1) type, phenylcoumaran (β-5) type, and pinoresinol (β-β) type structures, were proposed and identified by MALDI-TOF MS, giving a better understanding of the NiCu/C catalyzed lignin depolymerization.

Progress on Selective Catalytic Ammonia Oxidation (NH3‐SCO) over Cu−Containing Zeolite‐Based Catalysts

AbstractThe selective catalytic oxidation of ammonia into nitrogen and water vapor (NH3‐SCO) has proven to be the most efficient technique for the removal of NH3 from the oxygen‐containing diesel exhausts. Until now, two reviews over investigated catalysts have been published in 2015–2016 (Jabłońska et al., RCS. Adv. 2015; Appl. Catal. B: Environ. 2016). Among various NH3‐SCO catalysts, Cu‐ and/or Fe‐containing zeolites are considered as promising candidates due to their benign nature, NH3 storage capacity, very high NH3 conversion and N2 selectivity. The present review focusses only on the Cu‐containing zeolites (mainly on chabazite (CHA): SSZ‐13, SAPO‐34) catalysts) applied in NH3‐SCO starting from 2015. The synthesis/preparation methods and the state of Cu in catalysts on the activity and selectivity are highlighted. The advantages of the understanding of the reaction mechanism are reviewed. Finally, an outlook is given together with expected inspirations for future research directions in developing zeolite‐based catalysts.

Copper-Indium Binary Catalyst on a Gas Diffusion Electrode for High-Performance CO2 Electrochemical Reduction with Record CO Production Efficiency.

Cu-In metallic hybrid is a promising non-noble catalyst for selective electrochemical CO2 reduction (eCO2R) to CO, but the lack of direct assembly with a gas diffusion electrode (GDE) limits the further development of eCO2R to CO with both high Faradaic efficiency (FE) and high current density. In this study, an in situ electrochemical spontaneous precipitation (ESP) method was applied for the first time to prepare GDE-combined Cu-In electrocatalysts. The optimum Cu-In catalyst consists of a nanoscale "core-shell" structure of polycrystalline CuxO covered by the amorphous In(OH)3 interface. Higher than 90% FE of CO production has been achieved. With the synergy of a GDE flow cell and 1 M KOH catholyte, a current density of ∼200 mA cm-2 was reached at -1.17 V (reversible hydrogen electrode), which enabled a CO yield efficiency record of 3.05 mg min-1(CO2/15 mL min-1 with a 2 cm2 electrode). The ratios between CO and H2 produced can be effectively modulated via fine-tuning ESP conditions demonstrating possibility of generating CO or syngas with tuneable ratios. The present study provides a simple approach for constructing novel catalytic interfaces with dual active centers for eCO2R and other emerging electrochemical catalysis research.

Selective hydrogenation of acetic acid to ethanol on Cu-In catalyst supported by SBA-15

The supported copper based catalysts could be potential candidate for the selective catalytic hydrogenation of acetic acid to produce ethanol instead of noble metals. In this work, a series of highly efficient bimetallic Cu-In/SBA-15 catalysts were designed and prepared via the deposition-precipitation method. Detailed characterizations were carried out to investigate the textural properties, dispersion and chemical state of the metals, the interactions between copper and indium species, the adsorption and activation of acetic acid on the catalysts surface. The results clearly demonstrated the coexistence of Cu-In alloy and metallic Cu under the reductive reaction atmosphere. The strong synergistic effect inside Cu-In alloy not only accelerated the dissociation of acetic acid to acetate, but also hindered the combination of acetyl and ethoxy species to form ethyl acetate, thus promoting the catalytic hydrogenation performance significantly. It was also found that the concentration of adsorbed H atoms on catalysts was one of the indispensable factors affecting the ethanol selectivity, which was positively correlated to the exposed Cu surface area and H2 partial pressure. The optimal catalytic hydrogenation activity was obtained for 9Cu1In/SBA-15 under the reaction conditions of 2.5 MPa and 623 K, the conversion of acetic acid and selectivity of ethanol reached 99.1% and 90.9%, respectively. These results might provide an inspiration in the rational design of novel copper based catalysts for carboxylic acid hydrogenation.

Electrochemical training of nanoporous Cu-In catalysts for efficient CO2-to-CO conversion and high durability

Electrochemical carbon dioxide (CO2) reduction into valuable chemicals is usually implemented at high overpotential, and most bimetallic catalysts suffer from the dramatic evolution of surface composition especially in case of long-term operation. In this work, as a proof-of-concept experiment, one effective protocol is first identified to drive the positive evolution of surface contents on nanoporous Cu-In by electrochemical training in KHCO3 electrolyte. Interestingly, superior performances including high selectivity for CO production and robust reliability are realized. Thus, Faradaic efficiency can approach the maximum of 91% at −0.95 V (vs. RHE), and an excellent durability can be simultaneously testified by no detectable performance decay for 7 h in operation. More importantly, current investigation paves a new road for designing bimetallic electrocatalysts with high selectivity and long-term durability.

Dimethyl carbonate production via the oxidative carbonylation of methanol over Cu/SiO 2 catalysts prepared via molecular precursor grafting and chemical vapor deposition approaches

The influence of catalyst synthesis method and Cu source on the activity and selectivity of Cu/SiO 2 catalysts for the gas-phase oxidative carbonylation of methanol to dimethyl carbonate (DMC) is reported. [CuOSi(O t Bu) 3] 4, [CuO t Bu] 4, and CuCl were used as precursors to produce highly dispersed silica-supported copper. XANES and EXAFS characterization prior to reaction (but after thermal treatment under He) showed that Cu in the catalysts prepared with CuCl and [CuOSi(O t Bu) 3] 4 was present primarily as isolated Cu(I) species, whereas [CuO t Bu] 4 produced 1-nm Cu particles. During the catalytic reaction, the Cu in catalysts prepared from CuCl and [CuOSi(O t Bu) 3] 4 formed highly dispersed CuO moieties, whereas the Cu in catalysts prepared from [CuO t Bu] 4 formed a cuprous oxide layer over a Cu(0) core. For comparison, poorly dispersed Cu on silica was prepared via traditional incipient wetness impregnation with Cu(NO 3) 2. It was found that activity for DMC formation increased with increasing Cu dispersion. The selectivity for DMC formation (relative to CO) decreased with decreasing Cu dispersion when the original state of the Cu was Cu(0) directly preceding reaction conditions.