Plasmonic Au@Pd Nanoparticles Supported on a Basic Metal–Organic Framework: Synergic Boosting of H₂ Production from Formic Acid

We report synergistic catalysis of plasmonic Au@Pd nanoparticles supported on titanium-doped zirconium-based amine-functionalized metal–organic frameworks (MOFs) (UiO-66­(Zr_{100–<i>x</i>}Ti_<i>x</i>)) for boosting room-temperature hydrogen production from formic acid (HCOOH) under visible light irradiation. Our results revealed that the electronically promoted Pd sites by the localized surface plasmon resonance (LSPR) effect of Au as well as doping of amine functionality in the MOFs with titanium ions play crucial roles in achieving exceptional catalytic performance. Remarkably, a high H₂ production rate of 42000 mL h^–1 g^–1 (Pd) with high a turnover frequency (TOF) of 200 h^–1 based on Pd was obtained under visible light irradiation. Kinetic isotope effect (KIE) measurements demonstrated that dissociations of O–H and C–H bonds of formic acid, which are two important steps for hydrogen production from HCOOH, are individually facilitated by the assistance of amine groups within MOFs and active electron-rich Pd sites induced by the LSPR effect under visible light irradiation

Non-Noble-Metal Nanoparticle Supported on Metal–Organic Framework as an Efficient and Durable Catalyst for Promoting H₂ Production from Ammonia Borane under Visible Light Irradiation

In this work, we propose a straightforward method to enhance the catalytic activity of AB dehydrogenation by using non-noble-metal nanoparticle supported on chromium-based metal–organic framework (MIL-101). It was demonstrated to be effective for hydrogen generation from ammonia borane under assistance of visible light irradiation as a noble-metal-free catalyst. The catalytic activity of metal nanoparticles supported on MIL-101 under visible light irradiation is remarkably higher than that without light irradiation. The TOFs of Cu/MIL-101, Co/MIL-101, and Ni/MIL-101 are 1693, 1571, and 3238 h^–1, respectively. The enhanced activity of catalysts can be primarily attributed to the cooperative promoting effects from both non-noble-metal nanoparticles and photoactive metal–organic framework in activating the ammonia borane molecule and strong ability in the photocatalytic production of hydroxyl radicals, superoxide anions, and electron-rich non-noble-metal nanoparticle. This work sheds light on the exploration of active non-noble metals supported on photoactive porous materials for achieving high catalytic activity of various redox reactions under visible light irradiation

Efficient Catalytic Combustion of Cyclohexane over PdAg/Fe₂O₃ Catalysts under Low-Temperature Conditions: Establishing the Degradation Mechanism Using PTR-TOF-MS and <i>in Situ</i> DRIFTS

Cyclohexane, a typical volatile organic compound (VOC), poses high risks to the environment and humans. Herein, synthesized PdAg/Fe2O3 catalysts exhibited exceptional catalytic performance for cyclohexane combustion at lower temperatures (50% mineralization temperature (T50) of 199 °C, 90% mineralization temperature (T90) of 315 °C) than Pd/Fe2O3 (T50 of 262 °C, T90 of 335 °C) and Fe2O3 (T50 of 305 °C, T90 of 360 °C). In addition, PdAg/Fe2O3 displayed enhanced stability by alloying Ag with Pd. The redox and acidity of the PdAg/Fe2O3 were studied by XPS, H2-TPR, and NH3-TPD. In situ diffuse reflectance infrared Fourier transform spectroscopy and proton-transfer-reaction time-of-flight mass spectrometry were applied to identify the intermediates formed on the catalyst surface and in the tail gas during oxidation, respectively. Results suggested that loading PdAg onto Fe2O3 significantly enhanced the adsorption and activation of oxygen and cyclohexane, oxidative dehydrogenation of cyclohexane to benzene, and catalytic cracking of cyclohexane to olefins at low temperatures. This in-depth study will benefit the design and application of efficient catalysts for the effective combustion of VOCs at low temperatures

Synthesis of Ultralong Copper Nanowires for High-Performance Transparent Electrodes

Cu nanowires hold great promise for the fabrication of low-cost transparent electrodes. However, their current synthesis is mainly performed in aqueous media with poor nanowire dispersibility. We report herein the novel synthesis of ultralong single-crystalline Cu nanowires with excellent dispersibility, providing an excellent candidate material for high-performance transparent electrode fabrication

Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances

Heavily doped semiconductors have recently emerged as a remarkable class of plasmonic alternative to conventional noble metals; however, controlled manipulation of their surface plasmon bands toward short wavelengths, especially in the visible light spectrum, still remains a challenge. Here we demonstrate that hydrogen doped given MoO₃ and WO₃ via a facile H-spillover approach, namely, hydrogen bronzes, exhibit strong localized surface plasmon resonances in the visible light region. Through variation of their stoichiometric compositions, tunable plasmon resonances could be observed in a wide range, which hinge upon the reduction temperatures, metal species, the nature and the size of metal oxide supports in the synthetic H₂ reduction process as well as oxidation treatment in the postsynthetic process. Density functional theory calculations unravel that the intercalation of hydrogen atoms into the given host structures yields appreciable delocalized electrons, enabling their plasmonic properties. The plasmonic hybrids show potentials in heterogeneous catalysis, in which visible light irradiation enhanced catalytic performance toward <i>p</i>-nitrophenol reduction relative to dark condition. Our findings provide direct evidence for achieving plasmon resonances in hydrogen doped metal oxide semiconductors, and may allow large-scale applications with low-price and earth-abundant elements

Hierarchical Nanostructured WO₃ with Biomimetic Proton Channels and Mixed Ionic-Electronic Conductivity for Electrochemical Energy Storage

Protein channels in biologic systems can effectively transport ions such as proton (H⁺), sodium (Na⁺), and calcium (Ca⁺) ions. However, none of such channels is able to conduct electrons. Inspired by the biologic proton channels, we report a novel hierarchical nanostructured hydrous hexagonal WO₃ (<i>h</i>-WO₃) which can conduct both protons and electrons. This mixed protonic–electronic conductor (MPEC) can be synthesized by a facile single-step hydrothermal reaction at low temperature, which results in a three-dimensional nanostructure self-assembled from <i>h</i>-WO₃ nanorods. Such a unique <i>h</i>-WO₃ contains biomimetic proton channels where single-file water chains embedded within the electron-conducting matrix, which is critical for fast electrokinetics. The mixed conductivities, high redox capacitance, and structural robustness afford the <i>h</i>-WO₃ with unprecedented electrochemical performance, including high capacitance, fast charge/discharge capability, and very long cycling life (>50 000 cycles without capacitance decay), thus providing a new platform for a broad range of applications