Ping Song

High‐Performance Oxygen Reduction Electrocatalysts based on Cheap Carbon Black, Nitrogen, and Trace Iron

A real optimal Fe content: For N and Fe co-doped carbon electrocatalysts for oxygen reduction reactions (ORRs) it is found that there is a real optimal trace Fe content (Peak II), which has never been observed before. The real optimal electrocatalyst shows superior high activity for ORR and possesses the best price/performance ratio ever.

A Class of High Performance Metal-Free Oxygen Reduction Electrocatalysts based on Cheap Carbon Blacks

For the goal of practical industrial development of fuel cells, cheap, sustainable and high performance electrocatalysts for oxygen reduction reactions (ORR) which rival those based on platinum (Pt) and other rare materials are highly desirable. In this work, we report a class of cheap and high-performance metal-free oxygen reduction electrocatalysts obtained by co-doping carbon blacks with nitrogen and fluorine (CB-NF).The CB-NF electrocatalysts are highly active and exhibit long-term operation stability and tolerance to poisons during oxygen reduction process in alkaline medium. The alkaline direct methanol fuel cell with the best CB-NF as cathode (3u2005mg/cm2) outperforms the one with commercial platinum-based cathode (3u2005mg Pt/cm2). To the best of our knowledge, these are among the most efficient non-Pt based electrocatalysts. Since carbon blacks are 10,000 times cheaper than Pt, these CB-NF electrocatalysts possess the best price/performance ratio for ORR, and are the most promising alternatives to Pt-based ones to date.

Recent Advances in Heteroatom-Doped Metal-Free Electrocatalysts for Highly Efficient Oxygen Reduction Reaction

AbstractHeteroatom-doped metal-free electrocatalysts for oxygen reduction reaction (ORR) represent one of the most prominent families of electrocatalysts for fuel cells. While nitrogen (N)-doped carbon electrocatalysts toward ORR have experienced great progress throughout the past decades and yielded promising material concepts, also other heteroatom-doped catalysts have gained the researchers’ tremendous interest recently. Boron (B)-doping on carbon has been extensively studied, and due to the contrary electronic properties between N and B, a synergetic effect between the codoped N and B on carbon has been found for ORR. The carbons doped with sulfur (S), phosphorus (P), silicon (Si), and halogen (fluorine (F), chlorine (Cl), bromine (Br), iodine (I)) have also been studied as metal-free electrocatalysts for ORR in both experimental and theoretical ways. It has been known that the difference in electronegativity and size between the heteroatoms (N, B, S, P, Si, Cl, Br, I) and carbon can polarize adjacent carbon atoms to facilitate the oxygen reduction process. Especially, our research group reported the first F-doped or N,F-codoped carbon black as highly efficient ORR electrocatalysts which possess one of the best price/performance ratio ever. In this feature article, we review the recent research progress in the development of heteroatom-doped carbon-based metal-free electrocatalysts for ORR.n Graphical AbstractHeteroatom-doped metal-free electrocatalysts for oxygen reduction reaction represent one of the most prominent families of electrocatalysts that are used in fuel cells. In this feature article, we review the recent research progress in the development of heteroatom-doped carbon-based metal-free electrocatalysts for ORR.

High performance platinum single atom electrocatalyst for oxygen reduction reaction

For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680u2009mWu2009cm−2 at 80u2009°C with a low platinum loading of 0.09u2009mgPt cm−2, corresponding to a platinum utilization of 0.13u2009gPt kW−1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

Superresolution fluorescence mapping of single-nanoparticle catalysts reveals spatiotemporal variations in surface reactivity

Significance Here we use time-lapsed superresolution mapping of single-molecule catalysis events on individual nanoparticle surface to observe time-varying changes in the spatial distribution of catalysis events on Sb-doped TiO2 nanorods and Au triangle nanoplates. The ability to measure both the spatial- and time-resolved activity of different types of active sites on single-nanoparticle surface leads to a more comprehensive understanding of reactivity patterns and may enable the design of new and more productive heterogeneous catalysts. For the practical application of nanocatalysts, it is desirable to understand the spatiotemporal fluctuations of nanocatalytic activity at the single-nanoparticle level. Here we use time-lapsed superresolution mapping of single-molecule catalysis events on individual nanoparticles to observe time-varying changes in the spatial distribution of catalysis events on Sb-doped TiO2 nanorods and Au triangle nanoplates. Compared with the active sites on well-defined surface facets, the defects of the nanoparticle catalysts possess higher intrinsic reactivity but lower stability. Corners and ends are more reactive but also less stable than flat surfaces. Averaged over time, the most stable sites dominate the total apparent activity of single nanocatalysts. However, the active sites with higher intrinsic activity but lower stability show activity at earlier time points before deactivating. Unexpectedly, some active sites are found to recover their activity (“self-healing”) after deactivation, which is probably due to desorption of the adsorbate. Our superresolution measurement of different types of active catalytic sites, over both space and time, leads to a more comprehensive understanding of reactivity patterns and may enable the design of new and more productive heterogeneous catalysts.

Single-molecule chemical reaction reveals molecular reaction kinetics and dynamics

Understanding the microscopic elementary process of chemical reactions, especially in condensed phase, is highly desirable for improvement of efficiencies in industrial chemical processes. Here we show an approach to gaining new insights into elementary reactions in condensed phase by combining quantum chemical calculations with a single-molecule analysis. Elementary chemical reactions in liquid-phase, revealed from quantum chemical calculations, are studied by tracking the fluorescence of single dye molecules undergoing a reversible redox process. Statistical analyses of single-molecule trajectories reveal molecular reaction kinetics and dynamics of elementary reactions. The reactivity dynamic fluctuations of single molecules are evidenced and probably arise from either or both of the low-frequency approach of the molecule to the internal surface of the SiO2 nanosphere or the molecule diffusion-induced memory effect. This new approach could be applied to other chemical reactions in liquid phase to gain more insight into their molecular reaction kinetics and the dynamics of elementary steps.

Catalytic properties of graphitic and pyridinic nitrogen doped on carbon black for oxygen reduction reaction

Pure graphitic nitrogen (G-N) was doped on carbon black by Hummers method and a following heat treatment was used to transform the G-N to pyridinic (P)-N. An oxygen reduction reaction (ORR) study showed that the G-N site doped on carbon gave a two-electron ORR with H 2 O 2 as the main product, while the P-N site gave the four-electron process of ORR and decreased the production of H 2 O 2 . The results help the understanding and design of doped N-based ORR electrocatalysts.

Theoretical Study of Resorufin Reduction Mechanism by NaBH4

In the current work, the whole reduction mechanism of resorufin by sodium borohydride (NaBH4) has been investigated completely using quantum chemical theory for the first time. The possible pathways for each step were considered as much as possible. The calculated results reveal that the reduction mechanism for resorufin undergoes a nucleophilic addition with BH4(-), a synchronous proton abstraction from a carbon (C) atom, a protonation in a nitrogen (N) atom, and then a final hydrolysis process to obtain final reduced product dihydroresorufin. Interestingly, it was found that the protonation of N atom could induce a reduced product molecule with a Λ-type structure rather than a planar one, and the large alteration in geometry will induce different optical properties, such as fluorescent or nonfluorescent. More importantly, countercation Na(+) and solvation effect of H2O play important roles in reducing the activation energy in elementary steps, and their stabilization effect has been confirmed by NBO analysis. The detailed theoretical investigation for the reduction reaction of resorufin by NaBH4 will support some guidance for the similar reduction reaction for organic compounds like aldehydes and ketones.

A Bifunctional Highly Efficient FeNx/C Electrocatalyst

Herein, a type of Fe, N-codoped carbon electrocatalyst (FeNx /C, Fe-N-BCNT#BP) containing bamboo carbon nanotubes and displaying bifunctional high catalytic efficiency for both oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR) is reported. It shows high electrocatalytic activity and stability for both the ORR process with onset potential of 1.03 VRHE in alkaline and the CO2RR to CO with high faradic efficiency up to 90% and selectivity of about 100% at low overpotential of 0.49 V. For CO2RR to CO, it is revealed that Fe3 C is active but the activity of FeNx centers is lower than that of C-N-based centers, contrary with that observed for ORR. Due to its low cost and high electrocatalytic performance for these two reduction reactions, the obtained catalyst is very promising for extensive application in future. The revealed huge activity difference of the same types of active sites for different reactions can efficiently guide the synthesis of advanced materials with multifunction.

Ultrahigh pressure synthesis of highly efficient FeNx/C electrocatalysts for the oxygen reduction reaction

Ultrahigh pressure (UHP) was employed for the first time as a green method for the synthesis of highly efficient Fe, N co-doped carbon-based (FeNx/C) electrocatalysts for the oxygen reduction reaction (ORR). Compared with traditional pyrolysis under atmospheric conditions, the synthesis of FeNx/C catalysts under UHP could be done efficiently with much less consumption of time, energy and chemicals. The observed highly efficient synthesis and high ORR activity of such catalysts could be due to the fast heating system (12xa0°C per second) under UHP, which leads to highly efficient doping of heteroatoms on carbon with much less consumption of chemicals and energy; the UHP-induced high graphitization degree of the carbon support and the selective formation of highly active sites of pyridinic N and Fe–Nx for the ORR also contribute in part to the high ORR catalytic activity of the catalyst. The work presented here paves a new way for the green, environmentally friendly synthesis of heteroatom-doped highly efficient catalysts for energy or chemical processes.