C-H Activation Research Articles

Dual Pt atoms stabilized by an optimized coordination environment for propane dehydrogenation

Tailoring atomically dispersed catalysts by various methods has been the subject of intense current research in heterogeneous catalysis. In this work, the structural stability and propane dehydrogenation performance of Pt-TiO2 catalysts with single, dual, and triple Pt atoms doped on the reduced TiO2 surface have been examined. Experimental results indicate the atomically dispersed Pt is thermally very stable and shows exceptionally high activity (TOFpropane = 4.93 s−1) and selectivity (∼98.5 %) for the dehydrogenation reaction. The recently developed machine-learning-based SSW-NN method is then employed to explore the global potential energy surface of the atomically dispersed Pt atom-doped TiO2, which suggests that the single and dual Pt atoms can be tightly held by the vacancies created on the reduced transition-metal oxide, as confirmed by DFT + U calculated energetics. After that, advanced characterization techniques are used in conjunction with microkinetic analysis to establish the quantitative structure–activity relationships. It is found that the dual-Pt-atom structure with two Pt atoms embedded in adjacent Ti and O vacancies is the only active ensemble that dramatically promotes the CH bond activation and hydrogen recombination, as compared to single Pt atoms accommodated by either Ti or O vacancies. These results provide new and direct evidence in support of the idea that specific function can be imparted to specific active sites by tuning their coordination environments, which makes it possible to tailor the catalytic properties of metal oxides to a particular reaction such as propane dehydrogenation.

Ligand effect on Ru-centered species toward methane activation.

Ligands have been known to profoundly affect the chemical transformations of methane, yet significant challenges remain in shedding light on the underlying mechanisms. Here, we demonstrate that the conversion of methane can be regulated by Ru centered cations with a series of ligands (C, CH, CNH, CHCNH). Gas-phase experiments complemented by theoretical dynamic analysis were performed to explore the essences and principles governing the ligand effect. In contrast to the inert Ru+, [RuC]+, and [RuCNH]+ toward CH4, the dehydrogenation dominates the reaction of ligand-regulated systems [RuCH]+/CH4 and [RuCHCNH]+/CH4. In active cases, CH acts as active sites, and regulates the activation of CH4 assisted by the "seemingly inert" CNH ligand.

Engineering surface lattice hydroxyl groups toward highly efficient photocatalytic methane coupling.

Nb3O7(OH) containing abundant surface lattice hydroxyl groups, combining with loaded Au nanoparticles as the cocatalyst, was employed as a photocatalyst enabling highly efficient photocatalytic CH4 coupling to C2H6 under mild conditions. In situ spectroscopy technique revealed that the surface lattice hydroxyl groups play a vital role in promoting the activation of CH4 to produce the methoxy intermediates, contributing to significantly enhanced catalytic performance for CH4 conversion.

A triazole-based covalent organic framework as a photocatalyst toward visible-light-driven CO2 reduction to CH4.

Solar-light driven reduction of CO2 to CH4 is a complex process involving multiple electron and proton transfer processes with various intermediates. Therefore, achieving high CH4 activity and selectivity remains a significant challenge. Covalent organic frameworks (COFs) represent an emerging class of photoactive semiconductors with molecular level structural tunability, modular band gaps, and high charge carrier generation and transport within the network. Here, we developed a new heterocyclic triazole ring containing COF, TFPB-TRZ, through the condensation reaction between 1,3,5-tris(4-formylphenyl)benzene (TFPB) and 3,5-diamino-1,2,4-triazole (TRZ). The TFPB-TRZ COF with multiple heteroatoms shows suitable visible light absorption, high CO2 uptake capability and an appropriate band diagram for CO2 photoreduction. Photocatalysis results reveal a maximum CO2 to CH4 conversion of 2.34 mmol g-1 with a rate of 128 μmol g-1 h-1 and high selectivity (∼99%) using 1-benzyl-1,4-dihydronicotinamide (BNAH) and triethylamine (TEA) as sacrificial agents. Under similar reaction conditions in the presence of direct sunlight, the TFPB-TRZ COF displays a maximum CH4 yield of 493 μmol g-1 with a rate of 61.62 μmol g-1 h-1, suggesting the robustness and light-harvesting ability of the COF photocatalyst. A femtosecond transient absorption (TA) spectroscopy study shows fast decay of excited state absorption (ESA) in the COF compared to the TFPB building unit due to efficient electron transfer to the catalytic site in the framework. The mechanism of CO2 reduction to CH4 is studied by DFT-based theoretical calculation, which is further supported by an in situ diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) study. The DFT results reveal that the lone pair of electrons on nitrogen heteroatoms present in the triazole ring of the TRZ moiety help in the stabilization of the CO intermediate during CO2 to CH4 conversion. Overall, this work demonstrates the use of a metal-free, recyclable COF-based photocatalytic system for solar energy storage by CO2 reduction.

Asymmetric Cu-N-La Species Enabling Atomic-Level Donor-Acceptor Structure and Favored Reaction Thermodynamics for Selective CO2 Photoreduction to CH4.

Photocatalytic CO2 reduction into ideal hydrocarbon fuels, such as CH4 , is a sluggish kinetic process involving adsorption of multiple intermediates and multi-electron steps. Achieving high CH4 activity and selectivity therefore remains a great challenge, which largely depends on the efficiency of photogenerated charge separation and transfer as well as the intermediate energy levels in CO2 reduction. Herein, we construct La and Cu dual-atom anchored carbon nitride (LaCu/CN), with La-N4 and Cu-N3 coordination bonds connected by Cu-N-La bridges. The asymmetric Cu-N-La species enables the establishment of an atomic-level donor-acceptor structure, which allows the migration of electrons from La atoms to the reactive Cu atom sites. Simultaneously, intermediates during CO2 reduction on LaCu/CN demonstrate thermodynamically more favorable process for CH4 formation based on theoretical calculations. Eventually, LaCu/CN exhibits a high selectivity (91.6 %) for CH4 formation with a yield of 125.8 μmol g-1 , over ten times of that for pristine CN. This work presents a strategy for designing multi-functional dual-atom based photocatalysts.

Asymmetric Cu−N−La Species Enabling Atomic‐Level Donor‐Acceptor Structure and Favored Reaction Thermodynamics for Selective CO2 Photoreduction to CH4

AbstractPhotocatalytic CO2 reduction into ideal hydrocarbon fuels, such as CH4, is a sluggish kinetic process involving adsorption of multiple intermediates and multi‐electron steps. Achieving high CH4 activity and selectivity therefore remains a great challenge, which largely depends on the efficiency of photogenerated charge separation and transfer as well as the intermediate energy levels in CO2 reduction. Herein, we construct La and Cu dual‐atom anchored carbon nitride (LaCu/CN), with La‐N4 and Cu‐N3 coordination bonds connected by Cu−N−La bridges. The asymmetric Cu−N−La species enables the establishment of an atomic‐level donor‐acceptor structure, which allows the migration of electrons from La atoms to the reactive Cu atom sites. Simultaneously, intermediates during CO2 reduction on LaCu/CN demonstrate thermodynamically more favorable process for CH4 formation based on theoretical calculations. Eventually, LaCu/CN exhibits a high selectivity (91.6 %) for CH4 formation with a yield of 125.8 μmol g−1, over ten times of that for pristine CN. This work presents a strategy for designing multi‐functional dual‐atom based photocatalysts.

Selective catalytic reduction of NOX with CH4 over In/SSZ-13 zeolites: The enhancement of high-temperature catalytic activity by Ce modification

The selective catalytic reduction of nitrogen oxides by methane (CH4/NOX-SCR) is a potential technique for the abatement of the NOX emissions from lean-burn GDI engines, due to the excellent thermal stability of CH4. This work focuses on the promotion of In/SSZ-13 catalysts by Ce modification for the CH4/NOX-SCR performance at high temperatures. A series of In/SSZ-13 and Ce-In/SSZ-13 catalysts were prepared using the wetness impregnation method. The effects of Ce modification on the catalytic performance were analysed in detail using the scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectrum and temperature-programmed desorption/reduction techniques. The results show that the Ce modification significantly enhances the high-temperature activity of the In/SSZ-13 catalysts for the NOX-SCR reaction, especially for the 5 wt% Ce-15 wt% In/SSZ-13 sample which has more than 75% NOX conversion at 390–700 °C. In addition, the Ce modification enhances the water vapor tolerance of the catalyst sample. The Ce modification increases not only the concentration of surface chemisorption oxygen species, but also the relative amount of InO+ species which serve as the main active sites for CH4 activation. Furthermore, the incorporation of Ce into In/SSZ-13 greatly promotes NOX adsorption on the catalyst surface. Most importantly, the Ce modification makes In species well-dispersed on the catalyst surface and thus suppresses the formation of bulk In2O3 species which are more active for the CH4 non-selective oxidation. The combination of all these effects results in the Ce-In/SSZ-13 samples with the superior catalytic activity.

Gas-Phase Electrochemical Conversion of Methane on Boron-Doped Diamond Gas Diffusion Anodes

Methane as the primary component of natural gas is used as fuel for energy supply and serves as a major feedstock for the chemical industry to produce hydrogen. In addition, renewable methane is becoming available via thermochemical, photo- or electrochemical, and biogenic routes. It remains a challenge, however, to efficiently activate the C-H bond of methane while keeping the reaction kinetics under control to form value added products (hydrocarbons or alcohols) and avoid complete oxidation to CO2 [1]. A promising way to selectively activate the C-H bond of methane is to utilize reactive oxygen species (ROS) [2]. ROS play a major role in the partial electrochemical oxidation of water to produce hydrogen peroxide with boron-doped diamond (BDD) anodes [3]. However, little is known about the role of ROS towards CH4 activation under electrochemical conditions. The goal of our work is to achieve control over product selectivity in the gas-phase electrochemical conversion of methane towards methanol or C2+ products [4, 5]. We also aim to explore the role of water in the methane conversion mechanism using in-situ electrochemical FT-IR spectroscopy.Experimentally, we use a BDD coated mesh as gas-diffusion anode electrode in a zero-gap gas-phase electrolyzer. The anode side of the cell is fed with humidified or dry CH4 (or He for control experiments) and humidified He or H2O are fed to the cathode side (to keep the Nafion 117 membrane humidified). The electro-oxidation of water is paired with hydrogen evolution.. The scheme of the membrane electrode assembly is shown on Fig. 1. A.In this talk, we discuss the effects of water content, gas flow rate and methane pressure on product selectivity. We observe the formation of CO2 and CO along with O2 when humidified CH4 is fed to the anode side of the electrolyzer (and H2O is fed to the cathode). CO2 and CO originate from the oxidation of CH4, as confirmed by control experiment with only He fed to the anode (Fig. 1. B). This suggests that ROS, generated at the BDD electrode by water partial oxidation, can oxidize methane. However, O2 is still the major product even in the presence of CH4 and both conversion and selectivity are low. The missing Faradaic efficiency (Fig. 1. C) can be related to non-detected CH4 oxidation products – for this, we are currently deploying additional analytical techniques besides gas-chromatography, e.g., IR, NMR, and HPLC, to detect minor products in both gas and liquid phases.When running experiments with humidified CH4 gas feed on the anode and humidified He gas feed on the cathode, we observe that the CO to CO2 ratio increases. This indicates that the selectivity changes significantly while the cell (and the membrane) dries out. Hence, we propose that the product selectivity can be controlled by tuning the humidity level.Finally, in experiments with dry CH4 gas fed to the anode and H2O recirculated to the cathode, we observe that both the increase of the CH4 gas flow rate (from 10 to 20 cm3 min-1) and pressure (atmospheric, +1 and +2 bar) lead to a consistent increase of the CO2 and CO formation yield. Hence, controlling CH4 gas flow rate and pressure provides further opportunity to control the conversion and selectivity.The results achieved so far motivate us to further investigate the joint effect of the above parameters by using a membrane capable to operate under dry conditions, in a system with improved H2O management.

Effect of Pd/Pt decoration on MoSSe monolayer for CH4 signature through surface adsorption mechanism

Considering the current breakthrough in gas sensor technology, we have examined impact of CH4 in the vicinity of pristine MoSSe and Pd/Pt decorated MoSSe monolayers using first principles approach. The negative formation energies confirm structural stability of considered monolayers. The pristine MoSSe monolayer is semiconductor having 1.52 eV direct band gap. This value decreases in the presence of Pd/Pt adatom. Further, adsorption strength of CH4 to monolayers is validated by sensing parameters such as adsorption energy, recovery time, charge transfer and work function. Though we found maximum adsorption energies of − 0.674 and − 0.636 eV for adsorption on Se site of Pd/Pt decorated MoSSe monolayers, the overall sensing response also reveals high sensitivity for Se surface. However, both sites S and Se are favorable for CH4 adsorption. When CH4 is activated on Pd/Pt decorated monolayers, band gaps vary with marginal alterations and transform to direct type. Moreover, optical dielectric response alters strongly in the visible region after activation of CH4 on to Pd/Pt decorated MoSSe monolayers. This result identifies sensitivity response in the presence of methane which may detect CH4 gas easily in visible region. Generally, these interesting results of methane sensing study provoke Pd/Pt decorated MoSSe monolayers to be good sensing nano-device.

On the Mechanism Underlying the Distinct Activities of Rutile-Type Metal Oxides Toward Methane Activation

We report herein a density functional theory study on the C–H bond activation of CH4 over several rutile-type metal oxide catalysts, namely IrO2(110), TiO2(110), and β-MnO2(110) surfaces. We find that CH4 is strongly chemisorbed on the IrO2(110) surface, which distorts the CH4 geometry. Together with a strong thermodynamic driving force derived from the formation of Ir–CH3 bond, the H–CH3 bond activation proceeds with a negative barrier. In contrast, a weakly chemisorbed CH4 molecule on the TiO2(110) surface cannot proceed to the C–H bond cleavage due to a high activation barrier and a low thermodynamic driving force. The reaction on the β-MnO2(110) surface, on the other hand, is found to begin with a weak CH4 physisorption, followed by the C–H bond scission with a low activation barrier. However, here, the formation of •CH3 radical is more preferred than the Mn–CH3 bond formation, most possibly due to the electrophilic nature of MnO that suitably renders the catalyst as a perfect electron acceptor for the H-atom abstraction of CH4. With such low barrier and stability of the •CH3 formation, we suggest β-MnO2(110) as a potential catalyst that is good not only for the H–CH3 bond activation but also for the methanol formation.

Band structure engineering of Pd, Rh, Cu-Modified SrMoO4 for enhanced activity and selectivity in photocatalytic CO2 reduction to CH4

Photocatalytic CO2 reduction holds promise as a strategy to mitigate the energy crisis and greenhouse effects. However, devising cost-effective photocatalysts capable of efficiently and selectively converting CO2 to CH4 remains challenging. This study presents the synthesis of Pd, Rh, and Cu-modified SrMoO4 photocatalysts via a one-step solvothermal method. Our findings demonstrate increased CH4 activity and controlled selectivity through the modification with Pd, Rh, or Cu ions. It was determined that Pd, Rh, or Cu ions modified the SrMoO4 surface as -O-Pd-O-, -O-Rh-O-, or -O-Cu–O- species, increasing the adsorption sites and active regions on the catalyst surface. Moreover, these introduced -O-Pd-O-, -O-Rh-O-, or -O-Cu–O- species' energy level enhances visible light absorption and photogenerated charge carrier separation, and regulates the band structure for better alignment with water oxidation potential. This leads to greater water oxidation half-reaction efficiency and increased H+ generation in photocatalytic CO2 reduction. Consequently, more protons (H+) participate in CO2 photocatalytic reduction, thus promoting CH4 production and selectivity. These insights may guide the design of highly-selective photocatalysts for effective CO2 photoreduction through bandgap engineering strategies.

Single-Atom Ru Alloyed with Ni Nanoparticles Boosts CO2 Methanation.

Designing catalysts to proceed with catalytic reactions along the desired reaction pathways, e.g., CO2 methanation, has received much attention but remains a huge challenge. This work reports one Ru1Ni single-atom alloy (SAA) catalyst (Ru1Ni/SiO2) prepared via a galvanic replacement reaction between RuCl3 and Ni nanoparticles (NPs) derived from the reduction of Ni phyllosilicate (Ni-ph). Ru1Ni/SiO2 achieved much improved selectivity toward hydrogenation of CO2 to CH4 and catalytic activity (Turnover frequency (TOF) value: 40.00×10-3s-1), much higher than those of Ni/SiO2 (TOF value: 4.40×10-3s-1) and most reported Ni-based catalysts (TOF value: 1.03×10-3-11.00×10-3s-1). Experimental studies verify that Ru single atoms are anchored onto the Ni NPs surface via the Ru1-Ni coordination accompanied by electron transfer from Ru1 to Ni. Both in situ experiments and theoretical calculations confirm that the interface sites of Ru1Ni-SAA are the intrinsic active sites, which promote the direct dissociation of CO2 and lower the energy barrier for the hydrogenation of CO* intermediate, thereby directing and enhancing the CO2 hydrogenation to CH4.

Operando induced strong metal-support interaction of Rh/CeO2 catalyst in dry reforming of methane

Strong metal-support interaction (SMSI) is an important concept in heterogeneous catalysis that has a profound effect on the structure and activity of the supported metal catalyst. However, the catalyst with an uncontrolled SMSI state significantly prevents the accessibility of metal surface to reactants by encapsulation process which inevitably limits their practical application. Herein, we demonstrate that under the reaction condition of dry reforming of methane (DRM), the occurrence of SMSI (CO2-SMSI) can be operando induced between Rh and CeO2 which significantly improves the catalytic activity in DRM reaction. Detailed study has revealed that the formation of suitable Rhδ+/Rh0 species in CO2-SMSI is critical in improving CH4 activation, while the presence of permeable encapsulation layer is helpful to provide more active sites. This discovery provides a new approach to overcome the limitation of classical SMSI catalyst in DRM reaction.

Pseudo‐Para‐Substituted [2.2]Paracyclophanes for Hole Transport in Perovskite Solar Cells

Abstract2,2′,7,7′‐Tetrakis(N,N‐di‐p‐methoxyphenylamine)−9,9′‐spirobifluorene (spiro‐OMeTAD) is the prevalent hole transport layer in perovskite solar cells (PSCs) with regular device architecture. Yet, its spirobifluorene core and multistep synthesis make it rather expensive. For the further technological success of PSCs, novel scalable and inexpensive alternative hole transport layers are needed. Herein, a study of the structure‐property relations of pseudo‐para‐substituted [2.2]paracyclophanes is presented. Eight different hole transport materials are synthesized via double CH activation, eliminating metal‐containing substituents for cross‐coupling reactions. The ionization potentials (IPs) of the disubstituted paracyclophanes (DiPCPs) are examined by photoelectron spectroscopy in air, cyclic voltammetry and theoretical calculations. Through variation of donor groups and π‐linkers, IPs that span a range from 5.14 to 5.86 eV are achieved, demonstrating high customizability. From the eight novel materials, five showed good solubility and are implemented into PSCs. The solar cells with a hole transport layer of undoped 4,16‐di(4‐(2‐thienyl)‐N,N‐bis(4‐methoxyphenyl)aniline)[2.2]paracyclophane (DiPCP‐2) exhibit a power conversion efficiency of 12.7% ± 0.4%. The facile synthesis of DiPCP‐2 enables an estimated cost reduction by two thirds compared to spiro‐OMeTAD.

Insight into role of surface Sr‐sites in Sr/LOC‐HL catalyst for promoting low‐temperature oxidative coupling of methane

AbstractA series of Sr‐modified hedgehog‐like La2O2CO3 (Sr/LOC‐HL) catalysts were synthesized by the two‐step methods of coordination polymer induced formation and incipient wetness impregnation. Sr/LOC‐HL catalysts show the uniform nanorod morphology with width of 180 nm. The strong interaction between SrOx species and La2O2CO3 boosts the formation of active oxygen species for enhancing CH4 activation at low temperature. Sr/LOC‐HL catalysts show excellent catalytic performances for oxidative coupling of methane into C2+ hydrocarbons at low temperature (<500°C), and the selectivity is strongly dependent on the strong surface basic sites induced by the SrOLa bond. The Sr10/LOC‐HL catalyst exhibits the best catalytic performance and stability for OCM reaction at low temperature, that is, its CH4 conversion, C2+ selectivity, and yield at 450°C is 20.3%, 69.1%, and 13.2%, respectively; and its catalytic activity maintains stable during 3000 min. Insight into role of surface Sr‐sites would further improve catalytic performance at low temperature.

Upgrading renewable biogas into syngas via bi-reforming over high-entropy spinel-type catalysts derived from layered double hydroxides

The bi-reforming of biogas is of great significance for the consumption of greenhouse gases and the generation of valuable syngas. In this study, porous high-entropy spinel-type HE-MgAlO (up to quinary metals: Ni, Co, Zn, Ga, Mn,) catalysts derived from layered double hydroxide were prepared by the one-step co-precipitation method. The catalysts were characterized comprehensively via XRD, XRF, H2-TPR, CO2-TPD, XPS, SEM, HR-TEM, STEM-EDS, CH4-TPSR/CO2-TPO, TG-DSC, Raman, and so on. Compared to the monometallic Ni/MgAlO and binary NiCo/MgAlO catalysts, the HE-MgAlO catalyst exhibits higher initial CH4 (∼98 %) and CO2 (∼55 %) conversion and high stability up to 100 h under certain reaction conditions. The homogeneously-dispersed and electronically-enriched Ni sites, the oxophilic property and medium-strong basic sites of HE-MgAlO catalyst, lead to efficient activation of CH4 and CO2 (H2O), respectively, and high catalytic activity ultimately. The generation of reactive O* from CO2 (H2O) over oxophilic and medium-strong alkaline sites of HE-MgAlO catalyst prompts the rapid removal of coke precursors, leads to satisfying coke-resistant behavior. The spinel structure and strong metal-support interaction in HE-MgAlO catalyst enhances the thermal stability and results in satisfying anti-sintering performance.

Alkyne bridge engineering of donor-π-acceptor polymers for efficient CO2 reduction to CH4 and C2H4 under visible light illumination

Developing a conjugated polymer (CPs) for the formation of multi electron products or even C2 products from CO2 while simultaneously suppressing the 2-electron product (CO) is crucial for the efficient utilization of solar power. Herein, we investigated the donor-π-acceptor (D-π-A) CPs using cyclotriphosphonitrile, benzene and alkyne groups as the donor part, acceptor section and π-bridge structure, respectively. The photoinduced carrier separation and reduction capability of CPs can be well regulated by changing the number of π-bridges between the D and A units. Among them, three π-bridges (TTB-PCT) exhibit excellent CO2 reduction to CH4 (17.20 mmol g−1) or C2H4 (0.72 mmol g−1) activity under visible light illumination, which was obviously higher than two π-bridges (DTB-PCT) and four π-bridges (TTTB-PCT). TTB-PCT also exhibits excellent cycling stability (50 h). This research exhibits an innovative approach to exploit efficient metal-free CPs for photo-conversion CO2 into multi-electron products driven by visible light.

DFT studies on the reaction mechanism of Ru(II)-catalyzed the C[sbnd]H activation of aromatic amide and alkylation of non-active olefins

Density functional theory were performed to investigate the ruthenium-catalyzed CH activation of aromatic amides and alkylation of 1-hexene. Our findings indicate that the plausible catalytic cycles encompass CH activation, 1-hexene insertion, protonation, catalyst recovery, and the final product formation. Our calculations confirm that the [SbF6]− fragment remains positioned between ligand p-cymene and reactant aromatic amide(1a). Given that the reactant 1-hexene(2a) presents two potential reaction sites, a detailed discussion of the reaction branching point, resulting in two distinct products, is provided. The modified energy span model deduced that the turnover frequency (TOF) determining transition state (TDTS) and intermediate (TDI) correspond to the CC coupling transition states (TS5a or TS5b) and initial point, respectively. Considering the concentration effect of reactant 2a, the calculated apparent free-energy barriers for these two reaction pathways are 30.3 and 31.9 kcal mol−1. This difference offers a rational explanation for the observed experimental product ratio.

Iridium complexes of acridine-based PNP-type pincer ligands: Synthesis, structure and reactivity

Acridine-based PNP-type pincer ligands (AcrPNP) have previously been used for the construction of a small number of Ru(II), Mn(I), Rh(III) and Ir(III) complexes, with most attention being given to the catalytically-active ruthenium complexes. In the present work, we significantly expand the scope of known AcrPNP complexes by introducing a series of new Ir(I) and Ir(III) complexes. These were synthesized from two AcrPNP ligands differing in their P-substituents (iPr vs Ph), in conjunction with various Ir(I)-olefin precursors, through different sequences of reactions that include intramolecular CH activations and additions of H2 and NaBEt3H. The new iridium complexes, with their observed structures and reactivities, reflect the unique properties of the acridine-based PNP ligands, i.e., their inherent structural flexibility and ability to support both metal-centered reactivity (CH and HH oxidative addition) and ligand-centered reactivity (hydride- and H2-induced dearomatization).

Strong metal-support interactions between Pt and CeO2 for efficient methanol decomposition

Methanol decomposition is one of the most favorable chemical processes to alleviate the limitation of hydrogen storge and transportation. However, the different requirements of metal active sites for the activation of CH and OH bonds as well as strong adsorption of *CO intermediates limit the qualitative improvement of H2 generation for methanol decomposition. Herein, the Pt nanoparticles supported on nanorods of CeO2 with abundant oxygen defects (Pt/NR-CeO2-PD), prepared by photo-assisted deposition method, significantly boosted the H2 generation from methanol decomposition with an extremely high turnover frequency (TOF) of 84,225 h−1 and a large turnover number (TON) of 15,020,776 (200 h) at 300 °C. Mechanism investigations suggested that such superior catalytic performance was derived from the strong metal-support interaction of Pt/NR-CeO2-PD, in which the abundant oxygen defect of NR-CeO2 and high electronic density of Pt contributed to the efficient activation of OH and CH bonds, respectively. In addition, the down-shifting of d-band center of Pt further promoted the desorption of *CO intermediates. These findings may guide the design of new catalytic systems via construction of active sites for methanol decomposition.