Bimetallic manganese-vanadium functionalized N,S-doped carbon nanotubes as efficient oxygen evolution and oxygen reduction electrocatalysts
TL;DR: In this article, a bottom-up fabrication route using polyoxometalate metal precursors enables facile and scalable deposition of bimetallic catalysts on the carbon nanotubes.
Abstract: The electrochemical oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are two critical processes for energy conversion technologies, including water electrolysis, fuel cells, and metal-air batteries. For technological implementation, both reactions require highly active and stable electrocatalysts. Here, we report the simultaneous functionalization of carbon nanotubes with bimetallic manganese-vanadium OER/ORR catalytic sites, and nitrogen/sulfur atoms to increase electrical conductivity. A bottom-up fabrication route using polyoxometalate metal precursors enables facile and scalable deposition of bimetallic catalysts on the carbon nanotubes. Electrocatalytic OER/ORR studies show the high activity and stability of the composite under alkaline aqueous conditions, and comparable performance to commercial Pt/C (20 wt.%) was observed. Initial mechanistic analyses shed light on the effects of the bimetallic functionalization as well as the N/S-doping of the carbon nanotubes. In future, the use of heterometallic polyoxometalate precursors could allow the variation of metal types and atomic ratios, which could lead to well-defined bimetallic composites for various electrochemical processes.
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TL;DR: Carbon-based materials have multiple advantages including abundant sources, tunable molecular structures, high electronic conductivity, and environmental compatibility as mentioned in this paper. But, there is no systematic review yet covering all the general methods to boost carbon-based electrocatalysts for ORR/OER/HER, and reporting their most recent progress.
181 citations
TL;DR: In this paper, the authors summarized recent progress relating to the regulation of electrical behavior and electron distributions for the optimization of electrocatalytic water-splitting performance via defect engineering.
Abstract: As a potential energy carrier, hydrogen has surged up the priority list as part of broader decarbonization efforts and strategies to build or acquire clean energy economies. Driven by renewable electricity, electrochemical water splitting (WS) promises an ideal long-term, low-carbon way to produce hydrogen, with the ability to tackle various critical energy challenges. To improve the efficiency of electrocatalytic water splitting, electrocatalysts with enhanced conductivity, more exposed active sites, and high intrinsic activity are crucial for decreasing the energy gap for the rate-determining step (RDS) and subsequently improving the conversion efficiency. The incorporation of multidimensional imperfections has been demonstrated to be efficient for modulating the electron distribution and speeding up the electrocatalysis kinetics during electrocatalytic processes and this is now attracting ever-increasing attention. Herein, in this review, we summarize recent progress relating to the regulation of electrical behavior and electron distributions for the optimization of electrocatalytic water-splitting performance via defect engineering. With an emphasis on the beneficial aspects of the hydrogen economy and an in-depth understanding of electron redistribution caused by defect effects, we offer a comprehensive summary of the progress made in the last three to five years. Finally, we also offer future perspectives on the challenges and opportunities relating to water-splitting electrocatalysts in this attractive field.
135 citations
TL;DR: In this paper, a self-doped hollow-sphere porous carbon with a KOH to carbon mass ratio of 4 (NS-HPC-4) was obtained from abundant biomass puffball spores via a simple carbonization and KOH activation process for the first time.
103 citations
29 Apr 2015
TL;DR: In this paper, a dispersion of Mn and Co co-substituted Fe3O4 (MCF, Mn, Co, Fe = 1.1:1: 1:1) nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO) nanosheets was prepared by a hydrothermal method.
Abstract: A dispersion of Mn and Co co-substituted Fe3O4 (MCF, Mn : Co : Fe = 1 : 1: 1) nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO) nanosheets was prepared by a hydrothermal method. This catalyst exhibited 80% of the oxygen reduction reaction (ORR) activity of a Sigma 20 wt% Pt/C catalyst; and 61% of the oxygen evolution reaction (OER) activity of a 20 wt% RuO2/C catalyst in alkaline solution. Extensive material characterizations by field-emission transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, and inductively coupled plasma mass spectrometry (ICP-MS) were undertaken to suggest some possible reasons for the good electrochemical performance. The catalyst also delivered good performance in full zinc–air cell tests where it was used in the air electrode. The MCF catalyst has effectively combined the ORR activity of manganese oxide, the OER activity of cobalt oxide; and the electronic conductivity of bulk Fe3O4 into an integrated bifunctional catalytic system; and its good contact with the N-rGO nanosheets also reduces the external transport resistance in oxygen electrocatalysis.
85 citations
TL;DR: This study would shed some lights for facile synthesis of exceptional OER catalyst by tailoring the electronic structure and doping transition metal(s).
80 citations
References
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TL;DR: A unified theoretical framework highlights the need for catalyst design strategies that selectively stabilize distinct reaction intermediates relative to each other, and opens up opportunities and approaches to develop higher-performance electrocatalysts for a wide range of reactions.
Abstract: BACKGROUND With a rising global population, increasing energy demands, and impending climate change, major concerns have been raised over the security of our energy future. Developing sustainable, fossil-free pathways to produce fuels and chemicals of global importance could play a major role in reducing carbon dioxide emissions while providing the feedstocks needed to make the products we use on a daily basis. One prospective goal is to develop electrochemical conversion processes that can convert molecules in the atmosphere (e.g., water, carbon dioxide, and nitrogen) into higher-value products (e.g., hydrogen, hydrocarbons, oxygenates, and ammonia) by coupling to renewable energy. Electrocatalysts play a key role in these energy conversion technologies because they increase the rate, efficiency, and selectivity of the chemical transformations involved. Today’s electrocatalysts, however, are inadequate. The grand challenge is to develop advanced electrocatalysts with the enhanced performance needed to enable widespread penetration of clean energy technologies. ADVANCES Over the past decade, substantial progress has been made in understanding several key electrochemical transformations, particularly those that involve water, hydrogen, and oxygen. The combination of theoretical and experimental studies working in concert has proven to be a successful strategy in this respect, yielding a framework to understand catalytic trends that can ultimately provide rational guidance toward the development of improved catalysts. Catalyst design strategies that aim to increase the number of active sites and/or increase the intrinsic activity of each active site have been successfully developed. The field of hydrogen evolution, for example, has seen important breakthroughs over the years in the development of highly active non–precious metal catalysts in acid. Notable advancements have also been made in the design of oxygen reduction and evolution catalysts, although there remains substantial room for improvement. The combination of theory and experiment elucidates the remaining challenges in developing further improved catalysts, often involving scaling relations among reactive intermediates. This understanding serves as an initial platform to design strategies to circumvent technical obstacles, opening up opportunities and approaches to develop higher-performance electrocatalysts for a wide range of reactions. OUTLOOK A systematic framework of combining theory and experiment in electrocatalysis helps to uncover broader governing principles that can be used to understand a wide variety of electrochemical transformations. These principles can be applied to other emerging and promising clean energy reactions, including hydrogen peroxide production, carbon dioxide reduction, and nitrogen reduction, among others. Although current paradigms for catalyst development have been helpful to date, a number of challenges need to be successfully addressed in order to achieve major breakthroughs. One important frontier, for example, is the development of both experimental and computational methods that can rapidly elucidate reaction mechanisms on broad classes of materials and in a wide range of operating conditions (e.g., pH, solvent, electrolyte). Such efforts would build on current frameworks for understanding catalysis to provide the deeper insights needed to fine-tune catalyst properties in an optimal manner. The long-term goal is to continue improving the activity and selectivity of these catalysts in order to realize the prospects of using renewable energy to provide the fuels and chemicals that we need for a sustainable energy future.
7,062 citations
TL;DR: The high activity of BSCF was predicted from a design principle established by systematic examination of more than 10 transition metal oxides, which showed that the intrinsic OER activity exhibits a volcano-shaped dependence on the occupancy of the 3d electron with an eg symmetry of surface transition metal cations in an oxide.
Abstract: The efficiency of many energy storage technologies, such as rechargeable metal-air batteries and hydrogen production from water splitting, is limited by the slow kinetics of the oxygen evolution reaction (OER). We found that Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3–δ (BSCF) catalyzes the OER with intrinsic activity that is at least an order of magnitude higher than that of the state-of-the-art iridium oxide catalyst in alkaline media. The high activity of BSCF was predicted from a design principle established by systematic examination of more than 10 transition metal oxides, which showed that the intrinsic OER activity exhibits a volcano-shaped dependence on the occupancy of the 3d electron with an e g symmetry of surface transition metal cations in an oxide. The peak OER activity was predicted to be at an e g occupancy close to unity, with high covalency of transition metal–oxygen bonds.
3,876 citations
TL;DR: In this article, the effect of oxidation on the structural integrity of multiwalled carbon nanotubes through acidic (nitric acid and a mixture of sulfuric acid and hydrogen peroxide) and basic (ammonium hydroxide/hydrogen peroxide), agents has been studied.
2,454 citations
TL;DR: A mesoporous carbon foam co-doped with nitrogen and phosphorus that has a large surface area and good electrocatalytic properties for both ORR and OER and is tested as an air electrode for primary and rechargeable Zn-air batteries.
Abstract: A co-doped carbon material, methods of making such materials, and electrochemical cells and devices comprising such materials are provided. The co-doped carbon material comprises a mesoporous carbon material doped with nitrogen and phoshporous (NPMC). The present NPMC exhibit catalytic activity for both oxygen reduction reaction and oxygen evolution reaction and may be useful as an electrode in an electrochemical cell and particularly as part of a battery. The present NPMC materials may be used as electrodes in primary zinc-air batteries and in rechargeable zinc-air batteries and many other energy systems.
2,425 citations
TL;DR: In this paper, Mesoporous graphene doped with both N and S atoms (N-S-G) was prepared in one step and studied as an electrochemical catalyst for the oxygen reduction reaction (ORR).
Abstract: Doping duo: Mesoporous graphene doped with both N and S atoms (N-S-G) was prepared in one step and studied as an electrochemical catalyst for the oxygen reduction reaction (ORR). The catalyst shows excellent ORR performance comparable to that of commercial Pt/C. The outstanding activity of N-S-G results from both the large number and the synergistic effect of the dopant heteroatoms.
1,936 citations