With increasing concerns for global warming, the solar‐driven photocatalytic reduction of CO2 into chemical fuels like methanol is a propitious route to enrich energy supplies, with concomitant reduction of the abundant CO2 stockpiles. Herein, a novel single atom‐confinement and a strategy are reported toward single ruthenium atoms dispersion over porous carbon nitride surface. Ruthenium single atom character is well confirmed by EXAFS absorption spectrometric analysis unveiling the cationic coordination environment for the single‐atomic‐site ruthenium center, that is formed by Ru‐N/C intercalation in the first coordination shell, attaining synergism in N–Ru–N connection and interfacial carrier transfer. From time resolved fluorescence decay spectra, the average carrier lifetime of the RuSA–mC3N4 system is found to be higher compared to m‐C3N4; the fact uncovering the crucial role of single Ru atoms in promoting photocatalytic reaction system. A high yield of methanol (1500 µmol g‐1 cat. after 6 h of the reaction) using water as an electron donor and the reusability of the developed catalyst without any significant change in the efficiency represent the superior aspects for its potential application in real industrial technologies.
In this work, we report a robust Ru phosphide (RuP) catalyst, which exhibits high propylene selectivity for propane dehydrogenation, whereas monometallic Ru nanoparticles (NPs) result in cracking. X-ray photoelectron spectroscopy, synchrotron X-ray absorption spectroscopy, transmission CO-IR of the reduced catalyst, and high-angle annular dark-field scanning transmission electron microscopy are used to identify the surface structure of NPs with different P/Ru atomic ratios, changing from Ru to Ru2P to RuP with increasing P loading. In addition to improving the olefin selectivity, increasing the P/Ru ratio leads to higher turnover rates and lowers the deactivation rate. P is thought to act as a structural promoter to reduce the Ru ensemble size, decreasing the hydrogenolysis rate. In addition, increasing the P/Ru ratio leads to a decrease in the energy of the Ru valence orbitals, which are suggested to weaken metal-adsorbate bond energies and reactant surface coverages.
the extensive use of fossil fuels not only causes severe environmental issues but also compromises efforts to attain a sustainable energy future. [1,2] This has made researchers to investigate cost-effective and non-polluting alternatives to produce energy in a greener manner, through such systems as photovoltaic cells, electrolyzers, and fuel cells. Among them, fuel cells have attracted great attention over the past few years. [1] These devices can convert the chemical energy in fuels such as hydrogen, alcohols, organic acids, and hydrazine into electricity, with high efficiency and minimal greenhouse gas emissions. Among the fuels used in fuel cells, hydrazine is of particular interest for the following three reasons: 1) It produces only N 2 and H 2 O and it does not release the greenhouse gas CO 2 or other harmful byproducts as fossil fuels do; 2) Hydrazine is relatively easy to store and transport with existing infrastructures, as it is liquid at room temperature; and 3) Direct hydrazine fuel cells (DHFCs) have a large theoretical cell voltage (+1.61 V) and higher energy/power density than many other fuel cells (e.g., compared with H 2 /O 2 fuel cell, which is considered one of the best fuel cells). [1] However, Single-atom catalysts (SACs) have aroused great attention due to their high atom efficiency and unprecedented catalytic properties. A remaining challenge is to anchor the single atoms individually on support materials via strong interactions. Herein, single atom Co sites have been developedon functionalized graphene by taking advantage of the strong interaction between Co 2+ ions and the nitrile group of cyanographene. The potential of the material, which is named G(CN)Co, as a SAC is demonstrated using the electrocatalytic hydrazine oxidation reaction (HzOR). The material exhibits excellent catalytic activity for HzOR, driving the reaction with low overpotential and high current density while remaining stable during long reaction times. Thus, this material can be a promising alternative to conventional noble metal-based catalysts that are currently widely used in HzOR-based fuel cells. Density functional theory calculations of the reaction mechanism over the material reveal that the Co(II) sites on G(CN)Co can efficiently interact with hydrazine molecules and promote the NH bond-dissociation steps involved in the HzOR.
Industrial low-temperature methane combustion catalyst Pd/Al 2 O 3 suffers from H 2 O-induced deactivation. It is imperative to design Pd catalysts free from this deactivation and with high atomic efficiency. Using a small-pore zeolite SSZ-13 as support, herein we report well-defined Pd catalysts with dominant active species as finely dispersed Pd cations, uniform PdO particles embedded inside the zeolite framework, or PdO particles decorating the zeolite external surface. Through detailed reaction kinetics and spectroscopic and microscopic studies, we show that finely dispersed sites are much less active than PdO nanoparticles. We further demonstrate that H 2 O-induced deactivation can be readily circumvented by using zeolite supports with high Si/Al ratios. Finally, we provide a few rational catalyst design suggestions for methane oxidation based on the new knowledge learned in this study.
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