Rational design and synthesis of superior electrocatalysts for ethanol oxidation is crucial to practical applications of direct ethanol fuel cells. Here, we report that the construction of Pd-Zn dual ...sites with well exposure and uniformity can significantly improve the efficiency of ethanol electro-oxidation. Through synthetic method control, Pd-Zn dual sites on intermetallic PdZn nanoparticles, Pd-Pd sites on Pd nanoparticles and individual Pd sites are respectively obtained on the same N-doped carbon coated ZnO support. Compared with Pd-Pd sites and individual Pd sites, Pd-Zn dual sites display much higher activity for ethanol electro-oxidation, exceeding that of commercial Pd/C by a factor of ~24. Further computational studies disclose that Pd-Zn dual sites promote the adsorption of ethanol and hydroxide ion to optimize the electro-oxidation pathway with dramatically reduced energy barriers, leading to the superior activity. This work provides valuable clues for developing high-performance ethanol electro-oxidation catalysts for fuel cells.
The oxidation of hydrocarbons to produce high value-added compounds (ketones or alcohols) using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and ...economic views. Herein, we successfully synthesized cobalt single atom site catalysts (Co SACs) with high metal loading of 23.58 wt.% supported on carbon nitride (CN), which showed excellent catalytic properties for oxidation of ethylbenzene in air. Moreover, Co SACs show a much higher turn-over frequency (19.6 h
−1
) than other reported non-noble catalysts under the same condition. Comparatively, the as-obtained nanosized or homogenous Co catalysts are inert to this reaction. Co SACs also exhibit high selectivity (97%) and stability (unchanged after five runs) in this reaction. DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water, which result in the robust catalytic performance for this reaction.
Oxygen-involved electrochemical reactions are crucial for plenty of energy conversion techniques. Herein, we rationally designed a carbon-based Mn–N2C2 bifunctional electrocatalyst. It exhibits a ...half-wave potential of 0.915 V versus reversible hydrogen electrode for oxygen reduction reaction (ORR), and the overpotential is 350 mV at 10 mA cm–2 during oxygen evolution reaction (OER) in alkaline condition. Furthermore, by means of operando X-ray absorption fine structure measurements, we reveal that the bond-length-extended Mn2+–N2C2 atomic interface sites act as active centers during the ORR process, while the bond-length-shortened high-valence Mn4+–N2C2 moieties serve as the catalytic sites for OER, which is consistent with the density functional theory results. The atomic and electronic synergistic effects for the isolated Mn sites and the carbon support play a critical role to promote the oxygen-involved catalytic performance, by regulating the reaction free energy of intermediate adsorption. Our results give an atomic interface strategy for nonprecious bifunctional single-atom electrocatalysts.
Single‐atomic‐site (SAS) catalysts, a new frontier of catalysts, always show extremely high atom efficiency and unexpected catalytic properties. Herein, a pyrolyzing coordinated polymer (PCP) ...strategy is developed, which is facile and widely applicable in the synthesis of a series of SAS catalysts including SAS‐Fe, SAS‐Ni, SAS‐Cu, SAS‐Zn, SAS‐Ru, SAS‐Rh, SAS‐Pd, SAS‐Pt, and SAS‐Ir. The as‐obtained SAS catalysts can be easily synthesized at gram scale and the metal loading of SAS‐Fe catalysts achieves a record value of 30 wt%, which meets the requirement of practical applications. Moreover, it is discovered that SAS‐Fe catalysts show unprecedented catalytic performance for epoxidation of styrene using O2 as the only oxidant (yield: 64%; selectivity: 89%), while Fe nanoparticles and ironporphyrin are inactive. This discovery is believed to pave the way for exploiting the unparalleled properties of SAS catalysts and promoting their industrial applications.
A facile and general pyrolyzing coordinated polymer (PCP) strategy is developed to synthesize single‐atomic‐site (SAS) catalysts. This PCP strategy can be expended to synthesize a series of SAS catalysts including SAS‐Fe, SAS‐Ni, SAS‐Cu, SAS‐Zn, SAS‐Ru, SAS‐Rh, SAS‐Pd, SAS‐Pt, and SAS‐Ir. Moreover, SAS‐Fe shows excellent catalytic performance in the epoxidation of styrene using 1 atm O2 as the only oxidant.
The hydrosilylation reaction is one of the largest-scale application of homogeneous catalysis and is widely used to enable the commercial manufacture of silicon products. However, considerable issues ...including disposable platinum consumption, undesired side reactions and unacceptable catalyst residues still remain. Here, we synthesize a heterogeneous partially charged single-atom platinum supported on anatase TiO2 (Pt1 δ+/TiO2) catalyst via an electrostatic-induction ion exchange and two-dimensional confinement strategy, which can catalyze hydrosilylation reaction with almost complete conversion and produce exclusive adduct. Density functional theory calculations reveal that unexpected property of Pt1 δ+/TiO2 originates from atomic dispersion of active species and unique partially positive charge Ptδ+ electronic structure that conventional nanocatalysts do not possess. The fabrication of single-atom Pt1 δ+/TiO2 catalyst accomplishes a reasonable use of Pt through recycling and maximum atom-utilized efficiency, indicating the potential to achieve a green hydrosilylation industry.
Development of single-site catalysts supported by ultrathin two-dimensional (2D) porous matrix with ultrahigh surface area is highly desired but also challenging. Here we report a cocoon silk ...chemistry strategy to synthesize isolated metal single-site catalysts embedded in ultrathin 2D porous N-doped carbon nanosheets (M-ISA/CNS, M = Fe, Co, Ni). X-ray absorption fine structure analysis and spherical aberration correction electron microscopy demonstrate an atomic dispersion of metal atoms on N-doped carbon matrix. In particular, the Co-ISA/CNS exhibit ultrahigh specific surface area (2105 m
g
) and high activity for C-H bond activation in the direct catalytic oxidation of benzene to phenol with hydrogen peroxide at room temperature, while the Co species in the form of phthalocyanine and metal nanoparticle show a negligible activity. Density functional theory calculations discover that the generated O = Co = O center intermediates on the single Co sites are responsible for the high activity of benzene oxidation to phenol.
Noble metals play a momentous role in heterogeneous catalysis but still face a huge challenge in selectivity control. Herein, we report isolating contiguous Pt atoms and forming Pt-Zn intermetallic ...nanoparticles as an effective strategy to optimize the selectivity of Pt catalysts. Contiguous Pt atoms are isolated into single atoms and Pt-Zn intermetallic nanoparticles are formed which are supported on hollow nitrogen-doped carbon nanotubes (PtZn/HNCNT), as confirmed by aberration-corrected high-resolution transmission electron microscopy and X-ray absorption spectrometry measurements. Interestingly, this PtZn/HNCNT catalyst promotes the hydrogenation of 4-nitrophenylacetylene to 4-aminophenylacetylene with a much higher conversion ( > 99%) and selectivity (99%) than the comparison samples with Pt isolated-single-atomic-sites (Pt/HNCNT) and Pt nanoparticles (Pt/CN). Further density functional theory (DFT) calculations disclose that the positive Zn atoms assist the adsorption of nitro group and Pt-Zn intermetallic nanoparticles facilitate the hydrogenation on nitro group kinetically.
Oxygen vacancy (O
v
) as well as O
v
migration in metal oxide are of great importance in structural evolution of active center in single-atom catalysts (SACs). Here, the interplay between invasive ...single Pt atom and native O
v
in SA-Pt/rutile TiO
2
(110) surface, as well as their synergetic effect on water dissociation are investigated by density functional theory (DFT) calculations. We show that importing Pt atom as Pt-ads, Pt
2c
, Pt
5c
and Pt
6c
modes could decelerate the O
v
migration effectively, especially in Pt
6c
mode. Under oxygen-rich conditions, Pt
6c
substitution could make oxygen O
v
formation easier, but migration harder. On Pt
6c
/Ti
1−
y
O
2−
x
1
(110) surface, as a bimetal center, Pt
4c
-Ti
5c
concave could not make water dissociation process easier; however, the O
2c
closed to Pt become a good proton acceptor to make water dissociation on Ti
5c
-O
2c
more convenient with the aid of topmost Ti
5c
.
Tuning the selectivity of metal catalysts is of paramount importance yet a great challenge. A new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is ...reported. A certain amount of Co atoms is introduced into Ru catalysts to compress the Ru lattice, as confirmed by aberration‐corrected high‐resolution transmission electron microscopy (HRTEM) and X‐ray absorption fine structure (XAFS) measurements. We discover that the lattice strain of Ru catalysts can greatly affect their selectivity, and Ru with 3 % lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4‐nitrostyrene to 4‐aminostyrene compared to pristine Ru (99 % vs. 66 %). Theoretical studies confirm that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group. This study provides a new guideline for designing metal catalysts with high selectivity.
Taking the strain: Introducing Co atoms into a Ru catalyst compressed the Ru lattice strain, thus further affecting catalytic selectivity for hydrogenation of 4‐nitrostyrene to 4‐aminostyrene. Theoretical studies reveal that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group.
Abstract The aim of this study was to develop and validate predictive models for assessing the risk of death in patients with acute diquat (DQ) poisoning using innovative machine learning techniques. ...Additionally, predictive models were evaluated through the application of SHapley Additive ExPlanations (SHAP). A total of 201 consecutive patients from the emergency departments of the First Hospital and Shengjing Hospital of China Medical University admitted for deliberate oral intake of DQ from February 2018 to August 2023 were analysed. The initial clinical data of the patients with acute DQ poisoning were collected. Machine learning methods such as logistic regression, random forest, support vector machine (SVM), and gradient boosting were applied to build the prediction models. The whole sample was split into a training set and a test set at a ratio of 8:2. The performances of these models were assessed in terms of discrimination, calibration, and clinical decision curve analysis (DCA). We also used the SHAP interpretation tool to provide an intuitive explanation of the risk of death in patients with DQ poisoning. Logistic regression, random forest, SVM, and gradient boosting models were established, and the areas under the receiver operating characteristic curves (AUCs) were 0.91, 0.98, 0.96 and 0.94, respectively. The net benefits were similar across all four models. The four machine learning models can be reliable tools for predicting death risk in patients with acute DQ poisoning. Their combination with SHAP provides explanations for individualized risk prediction, increasing the model transparency.
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