Methanolysis Of Ammonia Borane Research Articles

Methanolysis of ammonia borane catalyzed by NiO–CuO heterostructured nanosheets: cooperation of visible light and oxygen vacancy

Methanolysis of ammonia borane catalyzed by NiO–CuO heterostructured nanosheets: cooperation of visible light and oxygen vacancy

Built‐in Electric Field in Yolk Shell CuO‐Co3O4@Co3O4 with Modulated Interfacial Charge to Facilitate Hydrogen Production from Ammonia Borane Methanolysis Under Visible Light

AbstractDeveloping highly efficient and low‐cost catalysts is an endless challenge in the field of producing H2 from ammonia borane (AB). Herein, the manufacture of yolk‐shell CuO‐Co3O4@Co3O4 nanocomposites are reported by using Cu2O@CuO as a template, in which CuO‐Co3O4 is encapsulated into the Co3O4 hollow nanocubes. Due to the unique morphology and built‐in electric field (BIEF) induced by the CuO‐Co3O4 interface, the CuO‐Co3O4@Co3O4 nanocomposites display remarkable catalytic activity in AB methanolysis. The turnover frequency (TOF) is 24.8 min‐1 in the absence of light and significantly increases to 33.9 min‐1 when exposed to visible light. The experimental and theoretical calculations demonstrate that charge migration from CuO to Co3O4 results in the formation of dual active sites (Cu and Co sites) in charge of adsorption and activation of CH3OH and AB, respectively. Visible light‐induced acceleration is likely caused by type‐II heterojunction, which allows a large number of photogenerated electrons to accumulate in the CuO conduction band. This effectively activates the adsorbed CH3OH on the Cu site, rendering it easier to break the O−H bond. A plausible reaction mechanism involved the activation of the O−H bond of CH3OH, as the RDS is proposed according to the FT‐IR and kinetic isotope effect (KIE) experiments. This work offers an avenue to rationally design high‐performance yolk‐shell catalyst for rapid hydrogen production from AB methanolysis reaction under visible light.

High performance catalyst for metal catalysis coupled with photocatalysis and its catalytic ammonia borane methanolysis for hydrogen production

In the study, the influence and mechanisms of metal and non-metal dopants on the photochemical properties of the semiconductor catalyst g-C3N4 are investigated. The results reveal that doping Ni, Ru, and B on g-C3N4 results in significant alterations to the energy band structure, the band gap value decreases to 0.78 eV (Ru@g-C3N4), 0.69 eV (Ni@g-C3N4), 0.5 eV (RuB@B-g-C3N4), and 0.1 eV (NiB@B-g-C3N4) from the original value of 1.139 eV. The doping of metal and non-metal atoms can significantly enhance the light absorption capability and photothermal conversion efficiency of B-g-C3N4. The mechanism of ammonia borane (AB) dehydrogenation follows the stepwise dehydrogenation principle. AB molecules adsorb onto the active metal centers, and with the assistance of the catalytic sites, CH3OH molecules activate and attack the B–N bond in AB molecules, leading to the initial breakage of the B–N bond, the interaction between O atoms in CH3OH and N atoms in AB continues, forming NH3BH2(OCH3). Interactions between H(B) and H(O) result in the production of H2, the energy barrier for this reaction is 34.14 kcal/mol. Compared to dark conditions, RuB@B-g-C3N4 exhibits higher catalytic activity under light irradiation, the reaction time from 9′20″ reduce to 8′. This shows that there is a synergistic effect between photocatalytic AB methanolysis and conventional metal catalyzed AB methanolysis in the RuB@B-g-C3N4 catalytic system. The study provides the novel way for the development of dual-function catalysts combining metal catalysis and photocatalysis through Ru and B modification of g-C3N4.

Visible-light-induced electron density enrichment of the active sites in the core-satellite structured CuWO4@NiO for fast hydrogen generation from ammonia borane methanolysis

Catalytic dehydrogenation of ammonia borane (AB) is an integrated technology for producing hydrogen with promising applications in mobile fuel cells. However, its commercial prospect is significantly hampered by the high expenditure of precious metal catalysts. Herein, a low-cost and efficient Z-schemed core-satellite structured CuWO4@NiO nanocomposite catalyst was developed for the methanolysis of AB for fast hydrogen production. The experimental and theoretical calculation results revealed charge transfer between CuWO4 (core) and NiO (satellite), thus creating active Ni and Cu sites for the adsorption and activation of methanol and AB, respectively. When the CuWO4@NiO catalyst was irradiated with visible light, numerous photogenerated electrons were accumulated in the conduction band of NiO of CuWO4@NiO by virtue of the special Z-scheme heterojunction, resulting in the electron density enrichment of Ni sites. The electron-enriched Ni sites effectively activated the adsorbed methanol, thus making the O–H bond cleavage easier, which was identified as the rate-determining step in AB methanolysis using kinetic isotope effect experiments. Based on the special electronic and energy band structures, our CuWO4@NiO catalyst exhibited outstanding catalytic activity with a turnover frequency of 26.5 min−1 in AB methanolysis, surpassing most noble-metal-free catalysts reported in the literature. Our findings show that visible light can be applied as a useful tool to optimize the electronic states of both active sites of catalysts and adsorbed reactants. This study provides insight into the design of more efficient catalytic systems toward AB methanolysis for fast hydrogen evolution.

Amino-functionalized CuFe2O4 supported Pd nanoparticles as magnetically catalyst for H2 production from methanolysis of ammonia borane and hydrogenation of nitro aromatics

Small and equally distributed Pd nanoparticles (NPs) are tightly anchored on the surface of magnetic and amino (–NH2) functionalized CuFe2O4 to obtain magnetically separable CuFe2O4–NH2@Pd catalyst with core-shell structure. Compared to the inherent catalytic activity of CuFe2O4, the catalytic performance of CuFe2O4–NH2@Pd for dehydrogenation of ammonia-borane (AB) and concurrent hydrogenation of different nitro aromatics by H2 generated from AB methanolysis can be boosted more effectively than that of CuFe2O4@Pd, which is the control catalyst and is prepared by loading Pd NPs on pristine CuFe2O4. As electron donating groups, the –NH2 groups covalently bonded to the surface of CuFe2O4 play vital roles in stabilizing Pd NPs, providing strong metal-support interaction and rendering enhanced catalytic activity. However, we find that the catalytic performance of CuFe2O4, CuFe2O4@Pd and CuFe2O4–NH2@Pd for the hydrogenation reduction of mercapto-substituted nitro aromatics (p-nitrothiophenol, p-NTP) is far inferior to that for the reduction of nitroarenes that do not contain a sulfur substituent. Therefore, it is quite essential to research and develop the new-type catalysts with more excellent catalytic performance.

Rattle-structured CuO/Co3O4@C microspheres, a potent bifunctional catalyst for hydrogen production from ammonia borane hydrolysis and methanolysis

Engineering and fabricating cost-effective and high-performing bifunctional catalysts for ammonia borane (AB) hydrolysis and methanolysis is paramount for their commercial availability. A series of rattle-structured CuO/Co3O4@C microsphere bifunctional catalysts for AB hydrolysis and methanolysis were produced using a simple hard template etching approach. The CuO/Co3O4@C-4 (4 refers to designed the mole ratio of Cu/Co) exhibits the best activity with TOF of 18.8 and 26.8 molH2·molcat-1·min−1 for AB hydrolysis and methanolysis, respectively. It is discovered that the excellent performance is mainly attributed to its unique rattle structure and the synergetic effect between Co3O4 and CuO. Kinetic isotope effect (KIE) experiments and infrared spectroscopy were applied to investigate AB hydrolysis and methanolysis reaction mechanisms. A suggested mechanism for AB methanolysis on rattle-structured CuO/Co3O4@C-4 is proposed based on the experiment results. This work could provide useful guidance for the construction of high-performance bifunctional catalysts for AB hydrolysis and methanolysis for hydrogen production.

A step‐growth strategy to grow vertical porous aromatic framework nanosheets on graphene oxide: Hybrid material‐confined Co for ammonia borane methanolysis

AbstractThe rational synthesis of a two‐dimensional (2D) porous aromatic framework (PAF) with a controllable growth direction remains a challenge to overcome the limitation of traditional stacked 2D materials. Herein, a step‐growth strategy is developed to fabricate a vertically oriented nitrogen‐rich porous aromatic framework on graphene oxide (V‐PAF‐GO) using monolayer benzidine‐functionalized GO (BZ‐GO) as a molecular pillar. Then, the confined Co nanoparticle (NP) catalysts are synthesized by encapsulating ultra‐small Co into the slit pores of V‐PAF‐GO. Due to the high nitrogen content, large specific surface area, and adequate slit pores, the optimized vertical nanocomposites V‐PAF‐GO provide abundant anchoring sites for metal NPs, leading to ultrafine Co NPs (1.4 nm). The resultant Co/V‐PAF‐GO catalyst shows an extraordinary catalytic activity for ammonia borane (AB) methanolysis, yielding a turnover frequency value of 47.6 min−1 at 25°C, comparable to the most effective non‐noble‐metal catalysts ever reported for AB methanolysis. Experimental and density functional theory studies demonstrate that the electron‐donating effect of N species of PAF positively corresponds to the low barrier in methanol molecule activation, and the cleavage of the O–H bond in CH3OH has been proven to be the rate‐determining step for AB methanolysis. This work presents a versatile step‐growth strategy to prepare a vertically oriented PAF on GO to solve the stacking problem of 2D materials, which will be used to fabricate other novel 2D or 2D–2D materials with controllable orientation for various applications.

Non‐precious Metal Cu‐Ni Alloy Nanoparticles Supported on Porous Boron Nitride Fibers as Catalysts for Dehydrogenation from Methanolysis of Ammonia‐Borane**

AbstractDehydrogenation from methanolysis of ammonia borane is a promising strategy for the development of sustainable hydrogen energy. Developing an effective and inexpensive catalyst is essential. In our study, a series of Cu−Ni nanoparticles, in the form of alloy, are supported onto porous boron nitride fibers by impregnation reduction. Cu and Ni synergistically interact through the alloys, Cu0.9Ni0.1/p‐BN demonstrates excellent catalytic effect with high turnover frequency (27.1 min−1) and low activation energy (27.8 kJ/mol) at 298 K. Kinetics indicates that the catalyst concentration follows the quasi‐primary reaction. Moreover, the pores of the p‐BN supporter prevent agglomeration of the metal particles while limiting their size, as well as providing protection to the particles. After passing 8 cycles, the catalyst does not suffer from severe poisoning effects. This work greatly enriches the non‐precious metal catalyst system and plays a very meaningful role in the study of dehydrogenation from methanolysis of AB.

Preparation of carbon-supported NiCo alloy nanoparticles and evaluation of their catalytic activity in the methanolysis of ammonia borane

The present work reported the development of carbon-supported bimetallic NiCo nanoparticles for H2 production in the methanolysis of AB for electricity generation from fuel cells. It was investigated by powder X-ray diffraction (P-XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. The catalytic properties of the Ni0.19Co0.81/C catalyst were carefully evaluated in terms of catalytic performance, such as different temperatures, metal [NiCo] loadings, substrate [AB] concentrations, and recyclability in 10 runs. The resulting N0.19Co0.81/C catalyst exhibits good catalytic activity with a high initial TOF of 136.65 min−1 and activation energy of 33.38 kJ mol−1 for AB methanolysis. Moreover, in the recyclability test, the Ni0.19Co0.81/C catalyst maintained 95 % of its initial activity with 100 % conversion after ten runs.

Dramatic acceleration by visible light and mechanism of AuPd@ZIF-8-catalyzed ammonia borane methanolysis for efficient hydrogen production

The novel nanomaterials AuxPdy@ZIF-8 catalyze H2-producing ammonia borane methanolysis; the reaction is considerably boosted by visible-light irradiation and ZIF-8 surpassing other supports. KIE studies and DFT calculations delineate the mechanism.

Methanolysis of ammonia borane catalyzed by magnetically isolable RHODIUM(0) nanoparticles

This article reports the preparation and employment of rhodium (0) nanoparticles (Rh0NPs) on the surface of magnetite nanospheres, denoted as Rh0@Fe3O4, as magnetically isolable nanocatalyst in the methanolysis of ammonia borane (MAB). The monodispersed Fe3O4 nanospheres are fabricated by a simple technique and used as nanosupport for Rh0NPs which are well stabilized and homogeneously distributed on the surface of nanospheres with a mean particle size of 2.8 ± 0.5 nm. The as-synthesized Rh0@Fe3O4 has a remarkable TOF value of 184 min−1 in the MAB to produce H2 gas in RT. Most of all, Rh0@Fe3O4 nanocatalyst can be reused, evolving 3.0 mol of H2 gas for a mole of AB, keeping 100% of its initial activity even in the fourth reuse of MAB at 25 °C. Recovery of the Rh0@Fe3O4 nanocatalyst can be accomplished by simply approaching an external magnet, which eliminates many laborious catalyst removal steps in catalytic reactions. Reported are the outcomes of kinetic investigation, done by altering the concentration of substrate and catalyst together with temperature. Kinetic studies reveal that the catalytic MAB shows dependence on the concentration of reactants and temperature.

Smart Hydrogen Atoms in Heterocyclic Cations of 1,2,4-Triazolium-Type Poly(ionic liquid)s.

ConspectusDiscovering and constructing molecular functionality platforms for materials chemistry innovation has been a persistent target in the fields of chemistry, materials, and engineering. Around this task, basic scientific questions can be asked, novel functional materials can be synthesized, and efficient system functionality can be established. Poly(ionic liquid)s (PILs) have attracted growing interest far beyond polymer science and are now considered an interdisciplinary crossing point between multiple research areas due to their designable chemical structure, intriguing physicochemical properties, and broad and diverse applications. Recently, we discovered that 1,2,4-triazolium-type PILs show enhanced performance profiles, which are due to stronger and more abundant supramolecular interactions ranging from hydrogen bonding to metal coordination, when compared with structurally similar imidazolium counterparts. This phenomenon in our view can be related to the smart hydrogen atoms (SHAs), that is, any proton that binds to the carbon in the N-heterocyclic cations of 1,2,4-triazolium-type PILs. The replacement of one carbon by an electron-withdrawing nitrogen atom in the broadly studied heterocyclic imidazolium ring will further polarize the C-H bond (especially for C5-H) of the resultant 1,2,4-triazolium cation and establish new chemical tools for materials design. For instance, the H-bond-donating strength of the SHA, as well as its Bro̷nsted acidity, is increased. Furthermore, polycarbene complexes can be readily formed even in the presence of weak or medium bases, which is by contrast rather challenging for imidazolium-type PILs. The combination of SHAs with the intrinsic features of heterocyclic cation-functionalized PILs (e.g., N-coordination capability and polymeric multibinding effects) enables new phenomena and therefore innovative materials applications.In this Account, recent progress on SHAs is presented. SHA-related applications in several research branches are highlighted together with the corresponding materials design at size scales ranging from nano- to micro- and macroscopic levels. At a nanoscopic level, it is possible to manipulate the interior and outer shapes and surface properties of PIL nanocolloids by adjusting the hydrogen bonds (H-bonds) between SHAs and water. Owing to the interplay of polycarbene structure, N-coordination, and the polymer multidentate binding of 1,2,4-triazolium-type PILs, metal clusters with controllable size at sub-nanometer scale were successfully synthesized and stabilized, which exhibited record-high catalytic performance in H2 generation via methanolysis of ammonia borane. At the microscopic level, SHAs are found to efficiently catalyze single crystal formation of structurally complex organics. Free protons in situ released from the SHAs serve as organocatalysts to activate formation of C-N bonds at room temperature in a series of imine-linked crystalline porous organics, such as organic cages, macrocycles and covalent organic frameworks; meanwhile the concurrent "salting-out" effect of PILs as polymers in solution accelerated the crystallization rate of product molecules by at least 1 order of magnitude. At the macroscopic scale, by finely regulating the supramolecular interactions of SHAs, a series of functional supramolecular porous polyelectrolyte membranes (SPPMs) with switchable pores and gradient cross-sectional structures were manufactured. These membranes demonstrate impressive figures of merit, ranging from chiral separation and proton recognition to switchable optical properties and real-time chemical reaction monitoring. Although the concept of SHAs is in the incipient stage of development, our successful examples of applications portend bright prospects for materials chemistry innovation.

Formation of Irida-β-ketoimines and PCNamine-Ir(III) Complexes by Reacting Irida-β-diketones with Aliphatic Diamines: Catalytic Activity in Hydrogen Release by Methanolysis of H3N-BH3.

Aliphatic diamines [(H2N(CH2)nNHR) (a-d) n = 2: R = H (a), R = CH3 (b), R = C2H5 (c), n = 3, R = H (d) or rac-2-(aminomethyl)piperidine (e)] react with [IrH(Cl){(PPh2(o-C6H4CO))2H}] in THF to afford ketoimine complexes [IrH(Cl){(PPh2(o-C6H4CO))(PPh2(o-C6H4CN(CH2)nNHR))H}] (2a-2d) or [IrH(Cl){(PPh2(o-C6H4CO))(PPh2(o-C6H4CNCH2(C5H9NH)))H}] (2e), containing a bridging N-H···O hydrogen bond and a dangling amine. Complex 2e consists of an almost equimolar mixture of two diastereomers. In protic solvents, the dangling amine in complexes 2 displaces chloride to afford cationic acyl-iminium compounds, [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH(CH2)nNHR))]X (3a-3d, X = Cl) or [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CNHCH2(C5H9NH)))]Cl (3e) and (4a-4b, X = ClO4), with new hemilabile terdentate PCNamine ligands adopting a facial disposition. Complexes 3 contain the corresponding phosphorus atom trans to hydride and the amine fragment trans to acyl, while complexes 4 contain the amine trans to hydride. 3b and 4b consist of 80:20 and 95:5 mixtures of diastereomers, respectively, while 3e contains a 65:35 mixture. In the presence of KOH, intermediate cationic acyl-iminium complexes 3 transform into neutral acyl-imine [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CN(CH2)nNHR))] derivatives (5) with retention of the stereochemistry. Single-crystal X-ray diffraction analysis was performed on 2a, [3a]Cl, [3b]Cl, [4a]ClO4, and 5b. Complexes 2, 3, and 5 catalyze the methanolysis of ammonia-borane under air to release hydrogen. The highest activity is observed for ketoimine complexes 2.

Modulation the electronic structure of hollow structured CuO-NiCo2O4 nanosphere for enhanced catalytic activity towards methanolysis of ammonia borane

Rational construction of cost-efficient catalysts with high activity and durability for hydrogen production from ammonia borane (AB) methanolysis is highly desirable but remains a substantial challenge. In this work, we constructed a series of non-noble-metal based hollow CuO-NiCo2O4 nanospheres composite, in which the CuO-NiCo2O4-0.8 nanospheres exhibit robust catalytic activity with a high turnover frequency (TOF) of 23.2 molH2 molcat.−1 min−1 towards AB methanolysis. Systemic experimental and computational studies reveal the promotion of activity results from the synergistic effect between CuO and NiCo2O4. It is revealed the combination of CuO with NiCo2O4 caused the electrons migration among Cu, Ni and Co sites and the change of d-band centers of catalyst, thus enhancing the adsorption process of CH3OH and AB molecules on catalyst and subsequently promoting the catalytic activity. Moreover, the Co center in CuO-NiCo2O4 composite is recognized as active sites by DFT calculations. Mechanistically, the rate determining step is the dissociation of OH bond in CH3OH, which is confirmed by kinetic isotopic effect experiment. A plausible mechanism of methanolytic dehydrogenation of AB on CuO-NiCo2O4 was proposed based on experiment and DFT calculations. These findings should shed light on the rational construction of cost-efficient catalysts with high performance for hydrogen production from AB methanolysis.

Interfacial charge transfer induced dual-active-sites of heterostructured Cu0.8Ni0.2WO4 nanoparticles in ammonia borane methanolysis for fast hydrogen production

Ammonia borane (AB) methanolysis can be applied as an integrated technology for the storage and production of hydrogen with high efficiency and safety. However, the commercial applications of AB methanolysis are restricted by the high costs of noble metal–based catalysts. In this study, a series of cheap CuxNi1−xWO4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) catalysts have been designed for AB methanolysis. Among them, heterostructured Cu0.8Ni0.2WO4 exhibits the highest turnover frequency (TOF) of 59.0 molhydrogen min−1 molcat−1, which is among the most active noble metal–free catalysts. The catalytic activity of the catalysts is well maintained after eight catalytic cycles. It is experimentally and theoretically demonstrated that electron transfer occurs on the CuWO4/NiWO4 interface in Cu0.8Ni0.2WO4 nanoparticles, leading to the formation of dual active sites on the surface of heterostructured Cu0.8Ni0.2WO4. More importantly, it is discovered that the dual active sites, namely, Cu and Ni sites, account for the adsorption and activation of AB and CH3OH, respectively, which can cooperate together to boost the catalytic activity in a significant way. The plausible mechanism for AB methanolysis has also been proposed and the scission of O-H bond is identified to be the rate-determining step. The findings in this study could serve as guidance for the creation of novel catalysts with excellent performance and low cost in AB methanolysis.

Review on Hydrogen Production from Catalytic Ammonia Borane Methanolysis: Advances and Perspectives

Review on Hydrogen Production from Catalytic Ammonia Borane Methanolysis: Advances and Perspectives

Methanolysis of ammonia borane using binder‐free hierarchical Co@Ni metal‐organic framework nanocolumn arrays catalyst for hydrogen generation

Ammonia borane (AB) is a potential material for chemical hydrogen storage because of its outstanding stability, high hydrogen density, and the development of highly effective hierarchical catalysts for AB hydrolysis. Herein, the hierarchical Co@Ni metal-organic framework (MOF) nanocolumn arrays (NCAs) on nickel foam (NF) were fabricated through a simple hydrothermal reaction, and the prepared catalysts were characterized using different techniques. The hierarchical Co@Ni-MOFNCA/NF acts as a catalyst for AB methanolysis for hydrogen production. The catalysts exhibited outstanding performance towards AB methanolysis with the TOF of TOF of 20.54 mol H2 mol catalyst−1 min−1. As a result, the activation energy of the Co@Ni-MOF NCA catalyst is 39.72 kJ mol−1 which is compared with some commercial solid support materials such as Al2O3 and AC. Additionally, the effects of nanocatalyst loading and temperatures were studied for the Co@Ni-MOF NCA catalyst. Further, a complete investigation proposes that the outstanding catalytic performance of the Co@Ni-MOF NCA catalyst could be attributed to the synergy between Co and Ni-MOF NCA.

High Recyclability Magnetic Iron Oxide‐Supported Ruthenium Nanocatalyst for H2 Release from Ammonia‐Borane Solvolysis

AbstractWe report the high capacity of recycling of a technologically simple, easily recoverable, Ru@Fe3O4 magnetic nanocatalyst, efficient in the release of H2 from ammonia‐borane (AB) solvolysis, using H2O or methanol at room temperature (25 °C). The initially oxidized Ru small nanoparticles (2–4 nm) are well‐dispersed on an iron oxide support (i. e. super paramagnetic iron oxide of spinel structure, SPIO, as aggregates of 20 nm to a few μm). As nanocatalyst, this composite achieved short‐time (<10 min) AB full hydrolysis (3 equiv. H2, no NH3, [AB]=0.1 mol L−1) with a turnover frequency (TOF) of ca 20 min−1 (86 min−1 at 50 °C). The post‐catalysis characterization of the composite showed the formation of well‐defined crystalline hcp Ru(0) dispersed on the SPIO. The activity for full H2 release from AB is conserved over ten cycles, which is among the most effective recycling processes reported to date (a magnetic recycling is achieved in <2 min). Pleasingly, an even superior activity was found in the more challenging AB methanolysis, with a TOF up to ca 30 min−1 for full H2 release, achieved in a recycling process repeated over 8 cycles.

Ammonia borane methanolysis for hydrogen evolution on Cu3Mo2O9/NiMoO4 hollow microspheres

Catalytic methanolysis of ammonia borane (AB) is an integrated hydrogen storage-production technology with bright prospects; the development of robust and cheap catalysts is crucial for its wide applications. In this study, we developed heterostructured Cu3Mo2O9/NiMoO4 hollow spheres comprised of nanoplatelets as catalysts for AB methanolysis. The Cu3Mo2O9/NiMoO4 catalyst with the optimal Cu/Ni ratio exhibited robust reactivity with a turnover frequency (TOF) of 62.1 molhydrogen min−1 molcat−1, which is superior to other precious-metal-free catalysts ever reported in the literature. Based on the theoretical calculation results, it was found that the d band center of the heterostructured Cu3Mo2O9/NiMoO4 catalysts exhibited an up shift compared to those of single Cu3Mo2O9 and NiMoO4, which was favorable for the chemisorption of the reactants. In addition, it was revealed that the active Ni and Cu sites in Cu3Mo2O9/NiMoO4 catalysts were responsible for the adsorption and activation of CH3OH and AB, respectively. The rate-determining step of AB methanolysis over Cu3Mo2O9/NiMoO4 catalyst was identified, and a possible reaction mechanism was proposed. This study may provide a deeper understanding of the adsorption and activation behaviors of methanol and AB, cooperative roles of different active sites on the heterostructured catalyst, as well as the reaction mechanism, conducive to the rational design of inexpensive and high-performing catalysts for AB methanolysis for hydrogen production.

Modulating the Acidic Properties of Mesoporous Mox–Ni0.8Cu0.2O Nanowires for Enhanced Catalytic Performance toward the Methanolysis of Ammonia Borane for Hydrogen Production

Rational construction of inexpensive, highly efficient, and stable catalysts for ammonia borane (AB) methanolysis is in high demand but still remains a great challenge. In this work, we have successfully fabricated uniform Mox-Ni0.8Cu0.2O nanowires using a simple hydrothermal method followed by a post-calcination treatment and flexibly modulated the acidity of their surface by changing the amount of Mo introduced into Ni0.8Cu0.2O. The Mo0.1-Ni0.8Cu0.2O catalyst displayed strong catalytic activity toward AB methanolysis with an ultrahigh turnover frequency of 46.9 molH2 molcat.-1 min-1, which is even higher than some noble metal catalysts. In this work, an equation regarding the relationship between the quantity of moderated acid sites of catalysts and its corresponding activity toward AB methanolysis was first determined. A plausible mechanism for AB methanolysis catalyzed by Mox-Ni0.8Cu0.2O was proposed, and the benefits of the introduction of MoO3 to Ni0.8Cu0.2O for enhancing the catalytic performance were also discussed. These findings can form a basis for the rational construction of inexpensive catalysts with robust performance toward AB methanolysis for hydrogen production.