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Journal ArticleDOI

Zn Single Atom Catalyst for Highly Efficient Oxygen Reduction Reaction

Ping Song1, Mi Luo1, Xiaozhi Liu1, Wei Xing1, Weilin Xu1, Zheng Jiang1, Lin Gu1 
01 Jul 2017-Advanced Functional Materials (John Wiley & Sons, Ltd)-Vol. 27, Iss: 28, pp 1700802
TL;DR: In this article, a nitrogen-triggered Zn single atom catalyst was proposed for the oxygen reduction reaction process, demonstrating high catalytic activity and remarkable durability for the reaction process.
Abstract: The authors report first a new type of nitrogen-triggered Zn single atom catalyst, demonstrating high catalytic activity and remarkable durability for the oxygen reduction reaction process. Both X-ray absorption fine structure spectra and theoretical calculations suggest that the atomically dispersed Zn-N4 site is the main, as well as the most active, component with O adsorption as the rate-limiting step at a low overpotential of 1.70 V. This work opens a new field for the exploration of high-performance Pt-free electrochemical oxygen reduction catalysts for fuel cells.
Citations
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Journal ArticleDOI
TL;DR: A compositional encyclopedia of SACs is provided, celebrating the 10th anniversary of the introduction of this term, and examines the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis.
Abstract: Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

505 citations

Journal ArticleDOI
TL;DR: In this paper, a single-atom nanozyme (SAzyme) based on a zinc-based zeolitic-imidazolate-framework (ZIF-8)-derived carbon nanomaterial containing atomically dispersed zinc atoms was investigated.
Abstract: Single-atom catalysts (SACs), as homogeneous catalysts, have been widely explored for chemical catalysis. However, few studies focus on the applications of SACs in enzymatic catalysis. Herein, we report that a zinc-based zeolitic-imidazolate-framework (ZIF-8)-derived carbon nanomaterial containing atomically dispersed zinc atoms can serve as a highly efficient single-atom peroxidase mimic. To reveal its structure-activity relationship, the structural evolution of the single-atom nanozyme (SAzyme) was systematically investigated. Furthermore, the coordinatively unsaturated active zinc sites and catalytic mechanism of the SAzyme are disclosed using density functional theory (DFT) calculations. The SAzyme, with high therapeutic effect and biosafety, shows great promises for wound antibacterial applications.

477 citations

Journal ArticleDOI
TL;DR: A class of novel hollow porous carbons, featuring well dispersed dopants of nitrogen and single Zn atoms, have been fabricated, based on the templated growth of a hollow metal-organic framework precursor, followed by pyrolysis, which achieves efficient catalytic CO2 cycloaddition with epoxides.
Abstract: The development of efficient and low energy-consumption catalysts for CO2 conversion is desired, yet remains a great challenge. Herein, a class of novel hollow porous carbons (HPC), featuring well dispersed dopants of nitrogen and single Zn atoms, have been fabricated, based on the templated growth of a hollow metal-organic framework precursor, followed by pyrolysis. The optimized HPC-800 achieves efficient catalytic CO2 cycloaddition with epoxides, under light irradiation, at ambient temperature, by taking advantage of an ultrahigh loading of (11.3 wt %) single-atom Zn and uniform N active sites, high-efficiency photothermal conversion as well as the hierarchical pores in the carbon shell. As far as we know, this is the first report on the integration of the photothermal effect of carbon-based materials with single metal atoms for catalytic CO2 fixation.

445 citations

Journal ArticleDOI
TL;DR: In this paper, a competitive complexation strategy has been developed to construct a novel electrocatalyst with Zn-Co atomic pairs coordinated on N doped carbon support (Zn/CoN-C).
Abstract: A competitive complexation strategy has been developed to construct a novel electrocatalyst with Zn-Co atomic pairs coordinated on N doped carbon support (Zn/CoN-C). Such architecture offers enhanced binding ability of O2 , significantly elongates the O-O length (from 1.23 A to 1.42 A), and thus facilitates the cleavage of O-O bond, showing a theoretical overpotential of 0.335 V during ORR process. As a result, the Zn/CoN-C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions with a half-wave potential of 0.861 and 0.796 V respectively. The in situ XANES analysis suggests Co as the active center during the ORR. The assembled zinc-air battery with Zn/CoN-C as cathode catalyst presents a maximum power density of 230 mW cm-2 along with excellent operation durability. The excellent catalytic activity in acid is also verified by H2 /O2 fuel cell tests (peak power density of 705 mW cm-2 ).

414 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the stability of reaction intermediates of electrochemical processes on the basis of electronic structure calculations was analyzed and a detailed description of the free energy landscape of the electrochemical oxygen reduction reaction over Pt(111) as a function of applied bias was presented.
Abstract: We present a method for calculating the stability of reaction intermediates of electrochemical processes on the basis of electronic structure calculations. We used that method in combination with detailed density functional calculations to develop a detailed description of the free-energy landscape of the electrochemical oxygen reduction reaction over Pt(111) as a function of applied bias. This allowed us to identify the origin of the overpotential found for this reaction. Adsorbed oxygen and hydroxyl are found to be very stable intermediates at potentials close to equilibrium, and the calculated rate constant for the activated proton/electron transfer to adsorbed oxygen or hydroxyl can account quantitatively for the observed kinetics. On the basis of a database of calculated oxygen and hydroxyl adsorption energies, the trends in the oxygen reduction rate for a large number of different transition and noble metals can be accounted for. Alternative reaction mechanisms involving proton/electron transfer to ...

7,711 citations

Journal ArticleDOI
06 Feb 2009-Science
TL;DR: It is reported that vertically aligned nitrogen-containing carbon nanotubes (VA-NCNTs) can act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction in alkaline fuel cells.
Abstract: The large-scale practical application of fuel cells will be difficult to realize if the expensive platinum-based electrocatalysts for oxygen reduction reactions (ORRs) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, we report that vertically aligned nitrogen-containing carbon nanotubes (VA-NCNTs) can act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction in alkaline fuel cells. In air-saturated 0.1 molar potassium hydroxide, we observed a steady-state output potential of –80 millivolts and a current density of 4.1 milliamps per square centimeter at –0.22 volts, compared with –85 millivolts and 1.1 milliamps per square centimeter at –0.20 volts for a platinum-carbon electrode. The incorporation of electron-accepting nitrogen atoms in the conjugated nanotube carbon plane appears to impart a relatively high positive charge density on adjacent carbon atoms. This effect, coupled with aligning the NCNTs, provides a four-electron pathway for the ORR on VA-NCNTs with a superb performance.

6,370 citations

Journal ArticleDOI
TL;DR: In this article, the CNDO method has been applied to the cyclopropylcarbinyl and cyclobutyl cations, and has given results which are in very good accord with experimental data.

3,778 citations

Journal ArticleDOI
22 Apr 2011-Science
TL;DR: A family of non–precious metal catalysts that approach the performance of platinum-based systems at a cost sustainable for high-power fuel cell applications, possibly including automotive power.
Abstract: The prohibitive cost of platinum for catalyzing the cathodic oxygen reduction reaction (ORR) has hampered the widespread use of polymer electrolyte fuel cells. We describe a family of non-precious metal catalysts that approach the performance of platinum-based systems at a cost sustainable for high-power fuel cell applications, possibly including automotive power. The approach uses polyaniline as a precursor to a carbon-nitrogen template for high-temperature synthesis of catalysts incorporating iron and cobalt. The most active materials in the group catalyze the ORR at potentials within ~60 millivolts of that delivered by state-of-the-art carbon-supported platinum, combining their high activity with remarkable performance stability for non-precious metal catalysts (700 hours at a fuel cell voltage of 0.4 volts) as well as excellent four-electron selectivity (hydrogen peroxide yield <1.0%).

3,464 citations

Journal Article
TL;DR: In this article, a family of non-precious metal catalysts that approach the performance of platinum-based systems at a cost sustainable for high-power fuel cell applications, possibly including automotive power.
Abstract: Fuel cell catalysts synthesized from abundant metals approach the performance and durability of platinum at lower cost. The prohibitive cost of platinum for catalyzing the cathodic oxygen reduction reaction (ORR) has hampered the widespread use of polymer electrolyte fuel cells. We describe a family of non–precious metal catalysts that approach the performance of platinum-based systems at a cost sustainable for high-power fuel cell applications, possibly including automotive power. The approach uses polyaniline as a precursor to a carbon-nitrogen template for high-temperature synthesis of catalysts incorporating iron and cobalt. The most active materials in the group catalyze the ORR at potentials within ~60 millivolts of that delivered by state-of-the-art carbon-supported platinum, combining their high activity with remarkable performance stability for non–precious metal catalysts (700 hours at a fuel cell voltage of 0.4 volts) as well as excellent four-electron selectivity (hydrogen peroxide yield <1.0%).

2,974 citations