Metal‐containing nanoparticles (M‐NPs) in metal/nitrogen‐doped carbon (M‐N‐C) catalysts have been considered hostile to the acidic oxygen reduction reaction (ORR). The relation between M‐NPs and the ...active sites of metal coordinated with nitrogen (MNx) is hard to establish in acid medium owing to the poor stability of M‐NPs. Herein, we develop a strategy to successfully construct a new FeCo‐N‐C catalyst containing highly active M‐NPs and MN4 composite sites (M/FeCo‐SAs‐N‐C). Enhanced catalytic activity and stability of M/FeCo‐SAs‐N‐C is shown experimentally. Calculations reveal that there is a strong interaction between M‐NPs and FeN4 sites, which can favor ORR by activating the O−O bond, thus facilitating a direct 4 e− process. Those findings firstly shed light on the highly active M‐NPs and FeN4 composite sites for catalyzing acid oxygen reduction reaction, and the relevant reaction mechanism is suggested.
Highly active metal‐containing nanoparticles and FeN4 composite sites have been constructed. Experiment and calculation results reveal the enormous potential for activating the O−O bond and promoting the direct 4 e− dissociation pathway in the acidic oxygen reduction reaction (ORR), which could fundamentally improve ORR activity and inhibit the formation of reactive oxygen species.
Driven by the persisting poor understanding of the sluggish kinetics of the hydrogen evolution reaction (HER) on Pt in alkaline media, a direct correlation of the interfacial water structure and ...activity is still yet to be established. Herein, using Pt and Pt–Ni nanoparticles we first demonstrate a strong dependence of the proton donor structure on the HER activity and pH. The structure of the first layer changes from the proton acceptors to the donors with increasing pH. In the base, the reactivity of the interfacial water varied its structure, and the activation energies of water dissociation increased in the sequence: the dangling O−H bonds < the trihedrally coordinated water < the tetrahedrally coordinated water. Moreover, optimizing the adsorption of H and OH intermediates can re‐orientate the interfacial water molecules with their H atoms pointing towards the electrode surface, thereby enhancing the kinetics of HER. Our results clarified the dynamic role of the water structure at the electrode–electrolyte interface during HER and the design of highly efficient HER catalysts.
On nickel–platinum alloy nanoparticles under alkaline conditions, the reactivity of interfacial water varies with its structure and the order of water dissociation. The inclusion of nickel re‐orientates interfacial water molecules with their hydrogen atoms pointing towards the electrode surface, thereby enhancing the kinetics of the hydrogen evolution reaction (HER).
The performance of nanomaterials in electrochemical energy conversion (fuel cells) and storage (secondary batteries) strongly depends on the nature of their surfaces. Designing the structure of ...electrode materials is the key approach to achieving better performance. Metal or metal oxide nanocrystals (NCs) with high-energy surfaces and open surface structures have attained significant attention in the past decade since such features possess intrinsically exceptional properties. However, they are thermodynamically metastable, resulting in a huge challenge in their shape-controlled synthesis. The tuning of material structure, design, and performance on the nanoscale for electrochemical energy conversion and storage has attracted extended attention over the past few years. In this Account, recent progress made in shape-controlled synthesis of nanomaterials with high-energy surfaces and open surface structures using both electrochemical methods and surfactant-based wet chemical route are reviewed. In fuel cells, the most important catalytic materials are Pt and Pd and their NCs with high-energy surfaces of convex or concave morphology. These exhibit remarkable activity toward electrooxidation of small organic molecules, such as formic acid, methanol, and ethanol and so on. In practical applications, the successful synthesis of Pt NCs with high-energy surfaces of small sizes (sub-10 nm) realized a superior high mass activity. The electrocatalytic performances have been further boosted by synergetic effects in bimetallic systems, either through surface decoration using foreign metal atoms or by alloying in which the high-index facet structure is preserved and the electronic structure of the NCs is altered. The intrinsic relationship of high electrocatalytic performance dependent on open structure and high-energy surface is also valid for (metal) oxide nanomaterials used in Li ion batteries (LIB). It is essential for the anode nanomaterials to have optimized structures to keep them more stable during the charge/discharge processes for reducing damaging volume expansion via intercalation and subsequent reduced battery lifetime. In the case of cathodes, tuning the surface structure of nanomaterials should be one of the most beneficial strategies to enhance the capacity and rate performance. In addition, metal oxides with unique defective structure of high catalytic activity and carbon materials of porous structure for facilitating fast Li+ diffusion paths and efficiently trapping polysulfide are most important approached and employed in Li–O2 battery and Li–S battery, respectively. In summary, significant progress has already been made in the electrocatalytic field, and likely emerging techniques based on NCs enclosed with high-energy surfaces and high-index facets could provide a promising platform to investigate the surface structure–catalytic functionality at nanoscale, thus shedding light on the rational design of practical catalysts with high activity, selectivity, and durability for energy conversion and storage.
Abstract
Single‐atom Pt and bimetallic Pt
3
Co are considered the most promising oxygen reduction reaction (ORR) catalysts, with a much lower price than pure Pt. The combination of single‐atom Pt and ...bimetallic Pt
3
Co in a highly active nanomaterial, however, is challenging and vulnerable to agglomeration under realistic reaction conditions, leading to a rapid fall in the ORR. Here, a sustainable quasi‐Pt‐allotrope catalyst, composed of hollow Pt
3
Co (H‐PtCo) alloy cores and N‐doped carbon anchoring single atom Pt shells (Pt
1
N‐C), is constructed. This unique nanoarchitecture enables the inner and exterior spaces to be easily accessible, exposing an extra‐high active surface area and active sites for the penetration of both aqueous and organic electrolytes. Moreover, the novel Pt
1
N‐C shells not only effectively protect the H‐PtCo cores from agglomeration but also increase the efficiency of the ORR in virtue of the isolated Pt atoms. Thus, the H‐PtCo@Pt
1
N‐C catalyst exhibits stable ORR without any fade over a prolonged 10 000 cycle test at 0.9 V in HClO
4
solution. Furthermore, this material can offer efficient and stable ORR activities in various organic electrolytes, indicating its great potential for next‐generation lithium–air batteries as well.
Star performance: The shape and surface structure of star‐shaped gold nanoparticles (NPs) bounded by (331) and vicinal high‐index facets, now synthesized for the first time, can be tuned by varying ...the water content in the deep eutetic solvent. The results confirm that star‐shaped Au NPs exhibit superior activity for electrocatalytic reduction of H2O2. The ability to tune the shape offers insight into structure–functionality relationships.
Purpose The purpose of this study was to appraise the retear rate and clinical outcomes of platelet-rich plasma use in patients undergoing arthroscopic full-thickness rotator cuff repair. Methods We ...searched the Cochrane Library, PubMed, and EMBASE databases for randomized controlled trials comparing the outcomes of arthroscopic rotator cuff surgery with or without the use of platelet-rich plasma. Methodological quality was assessed by the Detsky quality scale. When there was no high heterogeneity, we used a fixed-effects model. Dichotomous variables were presented as risk ratios (RRs) with 95% confidence intervals (CIs), and continuous data were measured as mean differences with 95% CIs. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system was used to assess the quality of evidence for each individual outcome. Results Eight randomized controlled trials were included, with the sample size ranging from 28 to 88. Overall methodological quality was high. Fixed-effects analysis showed that differences were not significant between the 2 groups in retear rate (RR, 0.94; 95% CI, 0.70 to 1.25; P = .66), Constant score (mean difference, 1.12; 95% CI, −1.38 to 3.61; P = .38), and University of California at Los Angeles (UCLA) score (mean difference, −0.68; 95% CI, −2.00 to 0.65; P = .32). The strength of GRADE evidence was categorized respectively as low for retear, moderate for Constant score, and low for UCLA shoulder score. Conclusions Our meta-analysis does not support the use of platelet-rich plasma in the arthroscopic repair of full-thickness rotator cuff tears over repairs without platelet-rich plasma because of similar retear rates and clinical outcomes. Level of Evidence Level II, meta-analysis of Level I and II randomized controlled trials.
The effects of interactions of Pt nanoparticles with hybrid supports on reactivity towards ethanol oxidation in alkaline solution are investigated. Studies involve catalysts with identical Pt ...nanoparticles on six hybrid supports containing carbon powder and transition metal oxides (TiO2, ZrO2, SnO2, CeO2, MoO3 and WO3). In situ X-ray absorption spectroscopy (XAS) results evidence that metal-support interactions produce changes in the Pt 5d band vacancy, which appears to determine the catalytic activity. The highest and lowest activities are observed for Pt nanoparticles on hybrid supports containing TiO2 and CeO2, respectively. Further studies are presented for these two catalysts. In situ FTIR reflection spectroscopy measurements, taken using both multi-stepped FTIR spectroscopy (MS-FTIR) and single potential alteration FTIR spectroscopy (SPA-FTIR), evidence that the main product of ethanol oxidation is acetate, although signals attributed to carbonate and CO2 indicate some differences in CO2 production. Fuel cell performances of these catalysts, tested in a 4.5 cm2 single cell at different temperatures (40–90 °C) show good agreement with data obtained by electrochemical techniques. Results of this comprehensive study point out the possibility of compensating a reduction of noble metal load with an increase in activity promoted by interactions between metallic nanoparticles and a support.
•Pt nanoparticles on hybrid C-MOx supports have different EOR activities.•Metal-support interactions affect the Pt 5d vacancy.•EOR activity in alkaline solution follows the Pt 5d band vacancy.•Acetate is the main oxidation product but CO2 selectivity changes with support.•Fuel cell performances are in agreement with electrochemical and FTIR results.
Platinum (Pt) nanocatalysts as the best catalysts for direct methanol fuel cell (DMFC) still face a huge challenge such as high cost, low utilization rate, activity and stability to be improved. ...Adjusting the surface structure of Pt nanoparticles (NPs) to achieve high-index facets with more active sites is an effective method to resolve the problems. Furthermore, the controlled synthesis of high-index faceted Pt (HIF-Pt) nanocatalysts directly on carbon paper, which is an important component of membrane electrode, can greatly promote the practical application of HIF-Pt nanocatalysts in DMFC. Herein, the HIF-Pt nanocatalysts supported on carbon paper (HIF-Pt/CP) were realized by developing an electrochemically controlled synthesis method. The fishbone-like and concave cube shaped Pt NPs surrounded by some high-index facets such as (200), (220), and (311), were achieved by adjusting the frequency and treatment time of applied potential. Hence, these HIF-Pt/CPs exhibit excellent activity and stability towards methanol electrooxidation during both cyclic voltammetry characterization and potentiostatic test. Especially, the specific activities and mass activities of HIF-Pt/CP-1 Hz reached 3.78 mA·cm
−2
and 1.53 A·mg
−1
, which were 6.5 and 2.78 times higher than those of commercial Pt/C, respectively. And the direct growth of HIF-Pt NPs on carbon paper effectively improves the stability of the catalyst layer which shows great potential in the practical application in DMFC.
Graphical Abstract
•There is a debate about how to assess long-term adverse outcome of older patients after elective noncardiac surgeries.•Frailty is an independent risk of one-year mortality after elective noncardiac ...surgeries.•Routine assessment of older individuals with frailty before surgery should be considered.
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