Network-Like Platinum Nanosheets Enabled by a Calorific-Effect-Induced-Fusion Strategy for Enhanced Catalytic Hydrogenation Performance

In this paper, we report the construction of network-like platinum (Pt) nanosheets based on Pt/reduced graphite oxide (Pt/rGO) hybrids by delicately utilizing a calorific-effect-induced-fusion strategy. The tiny Pt species first catalyzed the H2-O2 combination reaction. The released heat triggered the combustion of the rGO substrate under the assistance of the Pt species catalysis, which induced the fusion of the tiny Pt species into a network-like nanosheet structure. The loading amount and dispersity of Pt on rGO are found to be crucial for the successful construction of network-like Pt nanosheets. The as-prepared products present excellent catalytic hydrogenation activity and superior stability towards unsaturated bonds such as olefins and nitrobenzene. The styrene can be completely converted into phenylethane within 60 min. The turnover frequency (TOF) value of network-like Pt nanosheets is as high as 158.14 h−1, which is three times higher than that of the home-made Pt nanoparticles and among the highest value of the support-free bimetallic catalysts ever reported under similar conditions. Furthermore, the well dispersibility and excellent aggregation resistance of the network-like structure endows the catalyst with excellent recyclability. The decline of conversion could be hardly identified after five times recycling experiments.

Highly efficient catalytic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid with bimetallic Pt-Cu alloy nanoparticles catalyst

Bimetallic platinum-copper alloy nanoparticles is a highly active catalyst for the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) under base-free conditions, with a high turnover frequency up to 135...

Copper(II) tetrakis(pentafluorophenyl)porphyrin: Highly Active Copper-based Molecular Catalyst for Electrochemical CO2 Reduction

We report a highly active copper-based catalyst for electrochemical CO2 reduction. Electrochemical analysis revealed that the maximum turnover frequency for CO2 to CO conversion reached to 1,460,000 s-1 at an...

Electrocatalytic H2 evolution promoted by a bioinspired (N2S2)Ni(II) complex

We have investigated a bioinspired (N2S2)Ni(II) electrocatalyst that produces H2 from CF3CO2H with a turnover frequency (TOF) of ~1,250 s–1 at low acid concentration (<0.043 M) in MeCN. A mechanism...

Subsurface Oxygen Defects Electronically Interacting with Active Sites on In2O3 for Enhanced Photothermocatalytic CO2 Reduction

Oxygen defects play an important role in many catalytic reactions. Increasing surface oxygen defects can be done through reduction treatment. However, excessive reduction blocks electron channels and deactivates the catalyst surface due to electron-trapped effects by subsurface oxygen defects. How to effectively extract electrons from subsurface oxygen defects which cannot directly interact with reactants is challenging and remains elusive. Herein, we report a metallic In-embedded In2O3 nanoflake catalyst over which the turnover frequency of CO2 reduction into CO increases by a factor of 866 (7615 h-1) and 376 (2990 h-1) at same light intensity and reaction temperature, respectively, compared to In2O3. Under electron-delocalization effect of O-In-(O)Vo-In-In structural units at the interface, the electrons in the subsurface oxygen defects are extracted and gather at surface active sites. This improves the electronic coupling with CO2 and stabilizes COOH intermediate. The study opens up new insights for exquisite electronic manipulation of oxygen defects.

Analysis of Preferred Mechanisms of CO Oxidation with Atomically Dispersed Pt1/TiO2 Using the Energetic Span Model

This work examines the mechanisms of low-temperature CO oxidation with atomically dispersed Pt on rutile TiO2 (110) using density functional theory and the energetic span model (ESM). Of the 13 distinct pathways spanning Eley-Rideal (ER), termolecular ER (TER), Langmuir-Hinshelwood(LH), Mars-Van Krevelen (MvK) mechanisms as well as their combinations, TER with CO-assisted CO2 desorption yields the highest turnover frequency (TOF). However, this pathway is ruled out because Pt is dynamically unstable in an intermediate state in the TER cycle, determined in a prior ab initio molecular dynamics study by our group. We instead find that a previously neglected pathway – the ER mechanism – is the most plausible CO oxidation route based on agreement with experimental TOFs and turnover-determining states. The preferred mechanism is sensitive to temperature, with LH becoming more favorable than ER and TER above 750 K. By comparing TOFs for Pt1/TiO2 with prior mechanistic studies of various oxide-supported atomically dispersed catalysts in the literature, we also attempt to identify the most viable metal and support materials for CO oxidation.

Co/Ba/La2O3 catalyst for ammonia synthesis under mild reaction conditions

Ruthenium catalysts may allow realization of renewable energy–based ammonia synthesis processes using mild reaction conditions (<400 °C, <10 MPa). However, ruthenium is relatively rare and therefore expensive. Here, we report a Co nanoparticle catalyst loaded on a basic Ba/La2O3 support and pre-reduced at 700 °C (Co/Ba/La2O3_700red) that showed higher ammonia synthesis activity at 350 °C and 1.0–3.0 MPa than two benchmark Ru catalysts, Cs+/Ru/MgO and Ru/CeO2. The synthesis rate of the catalyst at 350 °C and 1.0 MPa (19.3 mmol h−1g−1) was 8.0 times that of Co/Ba/La2O3_500red and 6.9 times that of Co/La2O3_700red. The catalyst showed activity at temperatures down to 200 °C. High-temperature reduction induced formation of a BaO-La2O3 nano-fraction around the Co nanoparticles, which increased turnover frequency, inhibited Co nanoparticle sintering, and suppressed ammonia poisoning. These strategies may also be appliable to nickel catalysts.

Carbon-Doping as Efficient Strategy for Improving Photocatalytic Activity of Polysilicon Supported Pd in Hydrogen Evolution from Formic Acid

Interest in cost-effective materials pushes researchers to the inexpensive and abundant semiconductors to use photons’ energy for generating electrons and holes required for photocatalytic transformations. At the same time, polysilicon is one of the economic semiconductors with a disadvantage of high bandgap which could be solved by carbon-doping. We employed this strategy to the synthesis of carbon-doped polysilicon by a new approach starting from citric acid and methyltrimethoxysilane. The nanocomposite obtained was utterly characterized, and compared with bare polysilicon; increased UV–Vis absorbance and shift to higher wavelengths were the most notable characteristics of the synthesized catalyst. The carbon-doped polysilicon was modified with Pd nanoparticles to obtain a new heterogeneous photocatalyst for the formic acid degradation. The decomposition of formic acid was photocatalyzed by the obtained nanocomposite with a hydrogen production turnover frequency of up to 690 h−1. Moreover, it was demonstrated that the catalyst is stable and recyclable.