Oxygen Reduction Performance Research Articles

Biomass-derived carbon material as efficient electrocatalysts for the oxygen reduction reaction

Despite the abundance of carbon in nature, a significant portion of the existing biomass carbon materials in livestock, agriculture, and marine fishery industry are currently being wasted. Utilizing sustainable carbon materials as an alternative to noble Pt-based catalysts is crucial step to convert widely available and low-cost biomass resources into clean energy systems. Therefore, the rational synthesis of carbon-based catalysts for oxygen reduction reaction (ORR) has become a hot research focus in the field of electrochemistry. In this study, the recent progress in the synthesis of ORR electrocatalysts using sustainable biomass resources was reviewed; the activation and synthesis strategies of various biomass resources, as well as the microstructure and oxygen reduction performance of the prepared carbon-based catalysts were investigated. It is hoped that this review article will promote the understanding of various parameters from biomass as precursors for catalyst preparation and make contribute to the transition of biomass resources from the wasted carbon materials to the main catalysts in future energy devices.

Regulating electronic structure of CoN4 with axial Co—S for promoting oxygen reduction and Zn-air battery performance

Regulating electronic structure of CoN4 with axial Co—S for promoting oxygen reduction and Zn-air battery performance

Construction of Li0.5La0.5TiO3 (LLTO)-In2O3 n-n step scheme heterostructure nanorods for drastically heightening the sensing behavior in H2S gas

Owing to the high risk of hydrogen sulfide (H2S) gas, detecting and measuring it in real-time is desired in many fields. In this work, we reported the preparation of the unique lanthanum lithium titanate (Li0.5La0.5TiO3) –In2O3 nanorods and applied them as H2S sensors. The results show that the LLTO-In2O3 heterostructure composite sensors exhibit excellent sensing performance for H2S. The LLTO-In2O3 sensors offer good n-type responses to H2S in a wide range of temperatures (50–400 °C). At the optimum operating temperature (160 °C), the maximum gas-sensitive response of the 1:1 LLTO-In2O3 composite sensor to 50 ppm H2S reaches 116.61, which is 28.51 times larger than that of the original LLTO sensor. The formation of n-n heterojunction structure between LLTO and In2O3 has synergistic effects on strengthening the gas sensitivity of the material. A considerable potential barrier formed at the LLTO-In2O3 heterojunction. An enormous resistance of the nanorods and a further excellent gas-sensitive response are achieved. Meanwhile, the oxygen vacancy (OV) concentration and oxygen reduction performance of the LLTO-In2O3 heterostructure is increased, and the energy band gap is reduced, further promoting the chemical adsorption of O2 and the formation of O− and O2− anions.

A novel epoxy coating with nanocatalytic anticorrosion performance achieved by single-atom Fe-N-C catalyst

In view of the critical importance of oxygen to corrosion evolution, to starve corrosion via depleting oxygen in coatings is a promising strategy. In this work, a novel nanocatalytic anticorrosion concept is proposed to design new coating with outstanding corrosion resistance. Different from the passive barrier of traditional coatings and self-repair after corrosion of current stimuli-feedback coatings, such coating could spontaneously eliminate internal diffused oxygen and greatly suppress the corrosion process. As a proof of concept, single-atom Fe-N-C electrocatalyst with isolated FeN4 active sites is synthesized by a simple confined carbonization method, exhibiting excellent oxygen reduction performance (E1/2 = 0.902 V). In composite coating, the evenly dispersed Fe-N-C compensates for the coating defects and serves as oxygen scavengers, which could actively adsorb and consume ambient oxygen, thereby preventing oxygen penetration to the metal substrate surface, eliminating the oxygen contribution to corrosion and significantly boosting the anticorrosion performance of epoxy coating. This in-situ mediation for oxygen in coating prevents metal substrate from receiving new supply of oxygen, while imparting active anticorrosion property to the coating.

Chemically embedding Co nanospheres in N-doped carbon nanosheets for enhanced zinc-air batteries

The next-generation oxygen electrochemical catalysts based on non-precious metals have been extensively studied for zinc-air batteries (ZABs). Among them, Co–N–C catalysts have attracted considerable attention due to their excellent oxygen catalytic performance. However, the synthesis of Co nanoparticles with uniform structure and distribution on conductive and stable substrates remains challenging. Herein, we have prepared cobalt nanoparticles chemically embedded in N-doped carbon nanosheets (Co@NCS) by a simple organic-inorganic hybrid molten salts method. Due to the multifunctional environment provided by the mixed salts, the Co@NCS can exhibit efficient oxygen reduction and evolution reaction (ORR/OER) performance, enabling them to be suitable in ZABs. The resulting ZABs has a considerable open-circuit voltage of 1.40 V, a good peak power density of 130.4 mW cm−2 and long cycle stability for 100 h at 10 mA cm−2.

Tuning the Coordination Microenvironment of Central Fe Active Site to Boost Water Electrolysis and Oxygen Reduction Activity.

In heterogeneous catalysis, single-atom catalysts are the frontier and important prototypes for many reactions, and revealing the intrinsic structure-activity relationship is presently a critical task, but remains challenging. In this work, water electrolysis and oxygen reduction performances of FeXYi N3 -i (X, Y = B, C, O, P and S; i= 0, 1) moiety in Fe-porphyrin are studied by the first-principles calculations, aiming at unraveling how and why tuning the coordination microenvironment of the active metal atom can improve the activity. It can be concluded that breaking the coordination shell symmetry breaks the well-accepted standard scaling relationship, adjusts *O adsorption behavior and thus optimizes the oxygen evolution reaction (OER) activity, for example, to an extremely low overpotential of 0.17V. In combination with the Fe atom spin configuration and ligand field theory, the dramatically improved OER activity can be well explained. In the present work, the significance of the coordination microenvironment of central metal atom in studies of electrocatalysis is highlighted.

Bimetallic zeolite imidazolium framework derived multiphase Co/HNC as pH-universal catalysts with efficient oxygen reduction performance for microbial fuel cells

Here, the metallic Co encapsulated in hierarchical porous nitrogen-doped carbon (Co/HNC) catalysts is synthesized by pyrolysis of bimetallic (Co, Zn) zeolite imidazolium framework (ZIF) precursors to facilitate oxygen reduction reaction (ORR) in microbial fuel cell (MFC). Importantly, the highly dispersed cobalt nanoparticles are completely encapsulated in the N-doped hierarchical porous carbon, with abundant metal-nitrogen active sites and high degree of graphitization, which is very favorable for the ORR process. As a result, the Co/HNC as pH-universal catalyst shows remarkable ORR properties in alkaline, acidic and neutral environments. More notably, the density functional theory (DFT) calculation demonstrates that the introduction of cobalt can reduce the ORR overpotential and improves the ORR catalytic activity. Furthermore, the assembled MFCs with Co/HNC as cathode catalysts also exhibit high power density of 1324.5 mWm−2, and an output voltage of 0.48 V. Consequently, the investigation provides a new perspective for preparing high-performance and stable electrocatalysts for MFC devices.

Preparation of F and N Co‐Doped Fe–N–C Catalyst and Evaluation of its Oxygen Reduction Performance

The problems of underdeveloped pores and high electrochemical impedance of oxygen reduction reaction (ORR) catalysts need to be urgently addressed. Heteroatoms F and N are doped on precursor Fe‐zeolitic imidazolate framework (ZIF)‐8 to increase the activity of Fe‐ZIF‐8‐derived porous carbon materials and a noble metal‐free high‐activity ORR catalyst F–N/FeNC with 3D interconnected porous structure and high conductivity is successfully prepared. Experiments show that the synergistic effect of CF ionic bonds, pyridinic‐N, pyrrolic‐N, graphitic‐N, FeNx sites, and CF semi‐ionic bonds in F–N/FeNC can improve the ORR activity of the F–N/FeNC. The developed F–N/FeNC is advantageous with excellent specific surface area, ultra‐high electrical conductivity, and extremely high ORR mass transfer efficiency. As such, the F–N/FeNC has a high onset potential of 0.95 V (vs RHE) and a half‐wave potential of 0.84 V (vs RHE), implying excellent ORR performance even better than commercially available Pt/C catalyst. In addition, the carefully prepared F–N/FeNC demonstrated higher long‐term durability and excellent resistance to methanol influence compared with commercially available Pt/C catalyst. The developed strategy provides new insights into heteroatom‐doped metal–organic frameworks as a precursor of ORR catalysts.

Metal-Organic-Framework-Derived Atomically Dispersed Mn-N-C Electrocatalysts Boosting Oxygen Reduction Modulated by Anion Exchange of Permanganate.

Mn-N-C materials have received increasing interest in recent years because of their low Fenton reactivity and ORR activity comparable to those of their Fe-N-C and Co-N-C counterparts. In this contribution, an atomically dispersed Mn-N-C electrocatalyst with a prominent oxygen reduction performance was constructed by employing a cationic Cd-MOF as a precursor that can facilely and accurately introduce MnO4- anions through anion exchange. The best-performing Mn-N-C catalyst displays a 0.96 V (vs RHE) Eonset (onset potential) and a 0.87 V (vs RHE) E1/2 (half-wave potential) in an alkaline solution, which exceed those of the benchmark Pt/C catalyst. In particular, the maximal power density of the self-made zinc-air battery reaches 200 mW·cm-2, surpassing that of most reported Mn-N-C materials.

Hybrid Carbon Supports Composed of Small Reduced Graphene Oxide and Carbon Nanotubes for Durable Oxygen Reduction Catalysts in Proton Exchange Membrane Fuel Cells.

We demonstrated highly active and durable hybrid catalysts (HCs) composed of small reduced graphene oxide (srGO) and carbon nanotubes (CNTs) for use as oxygen reduction reaction (ORR) catalysts in proton exchange membrane fuel cells. Pt/srGO and Pt/CNTs were prepared by loading Pt nanoparticles onto srGO and CNTs using a polyol process, and HCs with different Pt/CNT and Pt/srGO ratios were prepared by mechanically mixing the two components. The prepared HCs consisted of Pt/CNTs well dispersed on Pt/srGO, with catalyst HC55, which was prepared using Pt/srGO and Pt/CNTs in a 5:5 ratio, exhibiting excellent oxygen reduction performance and high stability over 1000 cycles of the accelerated durability test (ADT). In particular, after 1000 cycles of the ADT, the normalized electrochemically active surface area of Pt/HC55 decreased by 11.9%, while those of Pt/srGO and Pt/C decreased by 21.2% and 57.6%, respectively. CNTs have strong corrosion resistance because there are fewer defect sites on the surface, and the addition of CNTs in rGO further improved the durability and the electrical conductivity of the catalyst. A detailed analysis of the structural and electrochemical properties of the synthesized catalysts suggested that the synergetic effects of the high specific surface area of srGO and the excellent electrical conductivity of CNTs were responsible for the enhanced efficiency and durability of the catalysts.

Fe/N co-doped hierarchically porous carbon on N-doped carbon nanotubes towards oxygen reduction reaction

Rational design of efficient and durable non-noble transition metal doped carbon-based oxygen reduction electrocatalysts is the key to reduce catalyst cost and optimize fuel cell performance. Herein, hierarchically porous Fe/N co-doped porous carbon on N doped carbon nanotubes (Fe/N-C@NCNTs) are prepared via the pyrolysis of Fe-doped ZIF-8 embedded on polypyrrole nanotubes (PNTs). The as-prepared Fe/N-C@NCNTs electrocatalyst exhibits the limit current density of 5.7 mA cm−2 and the half-wave potential of 0.84 V (vs. RHE), indicating the excellent oxygen reduction performance. Furthermore, the electrocatalytic activity of Fe/N-C@NCNTs is only reduced by 7% after 650 min of the stability test. The remarkable oxygen reduction performance is attributed to the synergistic effects of abundant Fe-Nx-C active sites, high graphitization degree and hierarchically porous structure of electrocatalyst.

Constructing Pt and Pt/MoC Co‐Anchored on Nitrogen‐Doped Carbon Toward Excellent Methanol‐Resilient Oxygen Reduction Performance for Zinc‐Air Batteries

AbstractDrastically lowering the usage of platinum while enhancing activity and stability toward oxygen reduction is critical to promoting energy conversion efficiency in metal‐air batteries. Herein, an efficient oxygen reduction catalyst was rationally designed by constructing ultrasmall Pt and Pt/MoC dual active sites co‐anchored on nitrogen‐doped carbon. Owing to the synergistic effect of the dual active sites, the optimized Pt‐MoC@NC delivers superior oxygen reduction activity with ultralow Pt loading. Especially, the Pt‐MoC@NC shows robust methanol tolerance. As the cathodic catalyst, Pt‐MoC@NC based zinc‐air battery possesses outstanding performance with a large peak power density of 100 mW cm−2 and long charge‐discharge durability.

Ordered PtCo Intermetallics Featuring Nitrogen‐Doped Carbon Prepared by Surface Coating Strategy for Oxygen Reduction Reaction

AbstractImproving the activity and stability of Pt‐based electrocatalysts is essential for large‐scale commercial applications of fuel cells. The ordered Pt‐based alloy nanomaterials encapsulated by coating have attracted significant attention. Here, we displayed a surface coating strategy to synthesize structurally ordered PtCo alloy catalysts featuring nitrogen‐doped carbon (NC). Experimental results reveal that the sample with appropriate dopamine feeding content shows enhanced oxygen reduction activity and stability, which exhibits a mass activity of 1.36 mA ⋅ mg−1Pt and specific activity of 1.98 mA ⋅ cm−2, superior to those of excessive or low dopamine adding content samples and commercial Pt/C catalyst. The enhanced electrocatalytic performance of this catalyst was attributed to the combined effect including the protection of suitable thickness NC shells, strong electronic interaction and high ordering degree. In this work, the surface coating strategy provides available references to further improve the oxygen reduction performance of PtM alloy catalysts.

Development and activity enhancement of zirconium/vanadium oxides as micro-heterogeneous ceramic electrocatalyst for ORR in low temperature fuel cell

A porous nano-metal oxide composite consisting of zirconium oxide and vanadium oxide (ZrVNPs) was prepared using precipitation hydrothermal technique, followed by microwave sintering process in order to enhance the catalytic activity toward oxygen reduction reaction (ORR) which is a key reaction in the development of low-temperature fuel cell technology. Microwave sintering process conditions were optimized using response surface methodology models (RSM) and the optimized produced material was called ZrV-T. The physiochemical and electrochemical activities of the fabricated materials were investigated and the results elucidated that, the catalytic efficiency of prepared samples is influenced by morphology, lattice structure, and porosity, as well as metal–support interactions and interfacial structural changes that affect oxygen molecules adsorption and activation. The thermally treated composite (ZrV-T) exhibits higher oxygen reduction performance than the non-sintered material (ZrVNPs). Both materials have different half-wave potentials (E1/2 = −0.36 V) and (E1/2 = −0.29 V) for ZrVNPs and ZrV-T respectively. In addition, ZrV-T has a higher stability than the Pt/C catalyst in 0.1 M KOH solution by 4% after 120 min. Using ZrV-T is likely to reduce costs in FCs and promote the use of electrochemical energy devices and it may also be beneficial in other systems that promote catalytic activity.

Carbon-Based Electrocatalyst Design with Phytic Acid-A Versatile Biomass-Derived Modifier of Functional Materials.

Increasing energy demands exacerbated by energy shortages have highlighted the urgency of research on renewable energy technologies. Carbon materials that can be employed as advanced electrodes and catalysts can increase the accessibility of efficient and economical energy conversion and storage solutions based on electrocatalysis. In particular, carbon materials derived from biomass are promising candidates to replace precious-metal-based catalysts, owing to their low cost, anti-corrosion properties, electrochemical durability, and sustainability. For catalytic applications, the rational design and engineering of functional carbon materials in terms of their structure, morphology, and heteroatom doping are crucial. Phytic acid derived from natural, abundant, and renewable resources represents a versatile carbon precursor and modifier that can be introduced to tune the aforementioned properties. This review discusses synthetic strategies for preparing functional carbon materials using phytic acid and explores the influence of this precursor on the resulting materials’ physicochemical characteristics. We also summarize recent strategies that have been applied to improve the oxygen reduction performance of porous carbon materials using phytic acid, thereby offering guidance for the future design of functional, sustainable carbon materials with enhanced catalytic properties.

Fullerene-Derived Carbon Nanotubes and Their Electrocatalytic Properties in Oxygen Reduction and Zn-Air Batteries.

Carbon-based materials with superior electrochemical performances have been prepared from fullerenes by releasing their intrinsic advantages such as pentagon defects and π-electron carbons. To the best of our knowledge, fullerene-derived carbon nanotubes (CNTs) and their electrochemical behavior have not been experimentally investigated. In this work, in situ growth of CNT composites from fullerene is realized via a self-catalyzed process by employing an Fe-decorated fullerene (ferrocenylpyrrolidine C60) as the precursor and NH3 as the pyrolysis atmosphere. The results show that the in situ Fe doping in fullerene, the self-assembly of fullerene molecules, the pyrolysis temperature, and the NH3 flow play essential roles in the generation of CNTs. The as-prepared MN7-10/3 CNT composite exhibits efficient oxygen reduction performance with E1/2 = 0.82 V and Eon = 1.02 V vs the RHE. The flexible solid-state Zn-air battery constructed based on MN7-10/3 exhibits a superior power density (109.3 mW cm-2 at 180.9 mA cm-2) and long-term durability (the voltage remains at 95.6% of the initial value after discharging for 5000 s) compared with the benchmark Pt/C catalyst. The transformation of the Fe-decorated fullerene to CNTs reveals a new function of fullerenes and demonstrates a new solid-state synthetic method for CNTs.

One-pot derived thermodynamically quasi-stable triple conducting nanocomposite as robust bifunctional air electrode for reversible protonic ceramic cells

Reversible protonic ceramic cell (RePCC) is an efficient, scalable, and fuel-flexible energy conversion and storage technology. However, finding single-phase triple conducting (H+/O2-/e-) electrodes with high electrochemical activity, structural and thermomechanical stability still faces great challenges. Herein, we propose a thermodynamically quasi-stable triple conducting perovskite-perovskite nanocomposite as bifunctional RePCC air electrode with exceptional performance, which is composed of a Ba0.5Sr0.5Co0.8Fe0.2O3-δ-based mixed oxygen ion and electronic conductor and a BaZr0.1Ce0.7Y0.1Yb0.1O3-δ-based protonic conductor and synthesized through one-pot method. Some unique structure introduces increased number of active sites and rich two-phase boundary, and tailored two phase composition, which contributes to the superior performance for both oxygen reduction and evolution reactions. In addition, the intimate connection of the two phases, their cation interexchange characteristics and the thermodynamically quasi-stable composition in the nanocomposite brings the electrode matchable thermal compatibility to the electrolyte and high structural stability that accounts for the superior durability.

The promoting effect of interstitial hydrogen on the oxygen reduction performance of PtPd alloy nanotubes for fuel cells

The promoting effect of interstitial hydrogen on the oxygen reduction performance of PtPd alloy nanotubes for fuel cells

MOF-Derived Co and Fe Species Loaded on N-Doped Carbon Networks as Efficient Oxygen Electrocatalysts for Zn-Air Batteries

HighlightsA novel method is developed to prepare bifunctional oxygen electrocatalysts composed of Co nanoparticles and highly dispersed Fe loaded on N-doped carbon substrates by virtues of metal-organic frameworks and two different doping processes.The designed catalysts show comparable performance with commercial catalysts. Meanwhile, rechargeable Zn-air batteries with prepared catalysts demonstrate high peak power density and good cycling stability.The performance promotion originates from the synergy between Co nanoparticles and highly dispersed Fe, porous structures, large specific areas, and distinct three-dimensional carbon networks. Searching for cheap, efficient, and stable oxygen electrocatalysts is vital to promote the practical performance of Zn-air batteries with high theoretic energy density. Herein, a series of Co nanoparticles and highly dispersed Fe loaded on N-doped porous carbon substrates are prepared through a “double-solvent” method with in situ doped metal-organic frameworks as precursors. The optimized catalysts exhibit excellent performance for oxygen reduction and evolution reaction. Furthermore, rechargeable Zn-air batteries with designed catalysts demonstrate higher peak power density and better cycling stability than those with commercial Pt/C+RuO2. According to structure characterizations and electrochemical tests, the interaction of Co nanoparticles and highly dispersed Fe contributes to the superior performance for oxygen electrocatalysis. In addition, large specific surface areas, porous structures and interconnected three-dimensional carbon networks also play important roles in improving oxygen electrocatalysis. This work provides inspiration for rational design of advanced oxygen electrocatalysts and paves a way for the practical application of rechargeable Zn-air batteries.

Electrochemical Grafting of a Pyridinium‐Conjugated Assembly on Graphite for H 2 O 2 Electrochemical Production

Carbon materials have shown great promise as cost-effective electrocatalysts for H 2 O 2 electrochemical production. In this work, we prepare a series of well-defined pyridinium-conjugated graphite sheets via nucleophilic substitution reaction of graphite with pyridine derivatives in anodic oxidation process. A combination of experimental and computational investigations confirm that the pyridine derivatives are electrochemically grafted onto the armchair-type edges of graphitic layers, where the adjacent carbon atoms show the positively charged state by the intramolecular charge transfer. The strong charge delocalization on pyridinium-conjugated graphite sheets can yield the enhanced electrocatalytic performance for oxygen reduction on both of the activity and selectivity (above 97 %) for H 2 O 2 production. Moreover, we find that the yield of H 2 O 2 production is also affected by the H 2 O 2 decomposing capabilities of functional groups on pyridinium. As one kind of pyrolysis-free strategies, the proposed electrochemical grafting can serve as a molecularly precise regulation to develop nitrogen doped carbon materials for more applications.