Electrocatalysts For Zn Research Articles

Co/Co9S8 Nanofibers Decorated with Carbon Nanotubes as Oxygen Electrocatalysts for Zn–Air Batteries

Co/Co₉S₈ Nanofibers Decorated with Carbon Nanotubes as Oxygen Electrocatalysts for Zn–Air Batteries

Study of the Suitability of Corncob Biochar as Electrocatalyst for Zn–Air Batteries

There has been a recent increasing interest in Zn–air batteries as an alternative to Li-ion batteries. Zn–air batteries possess some significant advantages; however, there are still problems to solve, especially related to the tuning of the properties of the air–cathode which should carry an inexpensive but efficient bifunctional oxygen reduction (ORR) and oxygen evolution (OER) reaction electrocatalyst. Biochar can be an alternative, since it is a material of low cost, it exhibits electric conductivity, and it can be used as support for transition metal ions. Although there is a significant number of publications on biochars, there is a lack of data about biochar from raw biomass rich in hemicellulose, and biochar with a small number of heteroatoms, in order to report the pristine activity of the carbon phase. In this work, activated biochar has been made by using corncobs. The biomass was first dried and minced into small pieces and pyrolyzed. Then, it was mixed with KOH and pyrolyzed for a second time. The final product was characterized by various techniques and its electroactivity as a cathode was determined. Physicochemical characterization revealed that the biochar had a hierarchical pore structure, moderate surface area of 92 m2 g−1, carbon phase with a relatively low sp2/sp3 ratio close to one, and a limited amount of N and S, but a high number of oxygen groups. The graphitization was not complete while the biochar had an ordered structure and contained significant O species. This biochar was used as an electrocatalyst for ORR and OER in Zn–air batteries where it demonstrated a satisfactory performance. More specifically, it reached an open-circuit voltage of about 1.4 V, which was stable over a period of several hours, with a short-circuit current density of 142 mA cm−2 and a maximum power density of 55 mW cm−2. Charge–discharge cycling of the battery was achieved between 1.2 and 2.1 V for a constant current of 10 mA. These data show that corncob biochar demonstrated good performance as an electrocatalyst in Zn–air batteries, despite its low specific surface and low sp2/sp3 ratio, owing to its rich oxygen sites, thus showing that electrocatalysis is a complex phenomenon and can be served by biochars of various origins.

Glu-Co-Assisted Iron-Based Metal–Organic Framework-Derived FeCo/N Co-Doped Carbon Material as Efficient Bifunctional Oxygen Electrocatalysts for Zn–Air Batteries

A Zn–air battery serves as an energy storage solution to address fossil energy and environmental concerns. However, sluggish kinetics in oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) demand innovative, cost-effective, and stable bifunctional catalysts to replace precious metal catalysts. In this study, an FeCo-CNTs/KB catalyst was synthesized by pyrolyzing NH2-MIL-101(Fe) coated with glu-Co and conductive carbon (KB). This hierarchical structure comprises carbon nanotubes (CNTs) grafted onto a carbon matrix, housing abundant FeCo nanoparticles within the nanotubes or matrix. KB introduction enhances FeCo nanoparticle dispersion and fosters uniform CNT formation with smaller diameters, thus exposing active sites. Consequently, the FeCo-CNTs/KB catalyst exhibits remarkable bifunctional electrocatalytic activity: an ORR half-wave potential of 0.84 V and an OER overpotential of 0.45 V (10 mA cm−2). Furthermore, the FeCo-CNTs/KB catalyst in a secondary Zn–air battery showcases enduring charge–discharge performance (≥300 h).

Screening Spinel Oxide Supports for RuO2 to Boost Bifunctional Electrocatalysts for Advanced Zn–Air Batteries

AbstractThe compositing strategy offers great potential in designing bifunctional oxygen electrocatalysts for Zn–air batteries. Recent reports reveal that the couple of RuO2, serving as a benchmark oxygen evolution reaction (OER) catalyst, with other oxygen reduction reaction (ORR) catalysts is a wise choice to build highly efficient bifunctional electrocatalysts. However, the design criteria for ORR and OER activities of RuO2‐based composite catalysts are still unclear. Herein, a series of transition metal (Fe, Co, Mn, and Ni)‐doped spinel oxides are designed to support RuO2 nanorods for exploring the reaction mechanism. Through advanced technology, it is considered that increasing the content and binding energy of Co3+ and enhancing the oxidation state of Ru4+ is an efficient strategy to promote ORR and OER activities for RuO2/Co‐based spinel oxide composite catalysts. It is found that coupling Mn‐doping Co3O4 (CMO) supports with RuO2 can induce the highest catalytic activities in ORR/OER and excellent performance in rechargeable Zn–air batteries. Operando electrochemical impedance spectroscopy and theoretical calculation further prove the synergistic effect between RuO2 and CMO supports originated from the oxygen overflow to overcome the large barrier for oxygen desorption on RuO2 during OER and oxygen adsorption on CMO supports during ORR.

Highly dispersed Zn-N, S co-doped carbon for highly efficient electrocatalytic oxygen reduction

Supportive atomic Zn electrocatalysts exhibit excellent stability for oxygen reduction reaction (ORR) due to their fully occupied d orbitals of Zn, but their catalytic activity is not satisfactory. Whereas heteroatom doping can anchor the Zn atoms to achieve higher Zn loading; and additionally serve as auxiliary sites to enhance the catalytic activity of Zn sites. Herein, we present a method for the synthesis of N, S co-doped carbon with highly dispersed Zn (named Zn-NSC). The ORR activity of the Zn-NSC catalysts is optimized by adjusting the pyrolysis temperature and the atomic structure of the dopant molecules. The optimized Zn-NSC demonstrates significantly enhanced ORR electrocatalytic activity, this is attributable to its highly co-doping of N and S heteroatoms that are adjacent to Zn atoms. Specifically, the Zn-NSC3 catalyst exhibits remarkable ORR characteristics with excellent onset voltage (0.97 V vs RHE) and half-wave potential (0.87 V vs RHE), surpassing those of Pt/C (0.97 V and 0.85 V, respectively). Additionally, the Zn-NSC3 can be utilized as efficient cathode for Al-air batteries, achieving a high power density of 119.4 mW cm−2 and satisfactory discharge stability. This work proposes an approach for synthesizing low-cost and efficient ORR electrocatalysts for Al-air battery applications.

Recent progress in iron-series-element-based electrocatalysts for Zn–air batteries

This review has summarized recent iron series elements-based electrocatalysts (ISEEs) progress for Zn–air batteries, and the advantages, challenges, and improvement strategies relating to monometallic, dual, and ternary ISEEs are discussed.

Zeolitic imidazolite framework derived bifunctional N,P-codoped hollow carbon sphere electrocatalysts decorated with Co2P/Fe for rechargeable Zn–air batteries

Co2P nanoparticles and Fe–Nx species were anchored on N,P codoped hollow carbonized spheres by structural and active site engineering. This work provides a facile strategy for the construction of bifunctional electrocatalysts for Zn–air batteries.

Recent advances in trifunctional electrocatalysts for Zn–air batteries and water splitting

The recent advances of trifunctional electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and their applications in Zn–air battery and water splitting, are comprehensively reviewed.

The chemical state of iron species influence on the performance of Fe–N–C bifunctional electrocatalyst for Zn–air batteries

Fe–N–C materials have emerged as promising alternatives to precious metals for oxygen reduction reaction/oxygen evolution reaction (ORR/OER). In this study, a strategy is presented to investigate the influence of different chemical states of iron species in Fe–N–C materials on their electrocatalytic performance. Three Fe–N–C catalysts, containing either zero-valent Fe or Fe3O4 nanoparticles, are synthesized using acid pickling, high-speed centrifugation and ultrasound-assisted hydrothermal methods, respectively. The findings manifest that the chemical state of iron significantly affects the electrocatalytic activity of Fe–NX active sites, namely zero-valent Fe enhancing Fe–NX activity while Fe3O4 weakening its activity. Notably, the Fe@FeNC catalyst containing only zero-valent iron, demonstrates the only 0.621 V potential difference between the ORR half-wave potential and the OER potential at 10 mA cm−2. Furthermore, the rechargeable Zn–air battery assembled with Fe@FeNC as the air cathode exhibits a remarkable peak power density of 179.0 mW cm−2, excellent cycling stability over 210 h (with a cycle frequency of one every 10 min), and the minimal voltage gap of 0.710 V. These results reveal the significance of different chemical states of metal-based nanoparticles in Fe–NX activity of Fe–N–C catalysts and offer insights into the rational design of electrocatalysts with exceptional activity and versatile applications.

Boosting electrocatalytic hydrazine oxidation at single-crystalline Ni nanosheets with embedded NiZn

Hydrazine oxidation reaction (HzOR) plays a crucial role in direct hydrazine fuel cells and holds promise for replacing the kinetics-sluggish oxygen evolution reaction in splitting water. While Ni–Zn alloys exhibit exceptional activity for HzOR, their synthesis under mild conditions remains a challenge. Herein, a Ni–Zn nanosheet catalyst with NiZn inclusion was prepared on Ni foam by controllable chemical etching together with ethylene glycol reduction. X-ray diffraction and transmission electron microscopy confirmed the single-crystalline nature and the presence of intermetallic NiZn. The strong interaction between Ni and ZnO, along with defects, facilitated the formation of this intermetallic compound. The Ni–Zn/Ni foam exhibits remarkable catalytic activity (214.3 ​mA ​cm−2 at 0.1 ​V) and durability (87.8 ​% retention after 24 ​h) towards hydrazine electrooxidation, thanks to the combined benefits of intermetallic NiZn, mesoporous nanosheets, microscopic defects, single-crystalline characteristics, and a coherent Ni–NiZn interface. This study provides a new method for designing highly active Ni–Zn electrocatalysts for HzOR.

Free‐Standing Tunnel‐Structured MnO2 Nanorods‐Doped with Nickel and Cobalt Cations as Bifunctional Electrocatalysts for Zn–Air Batteries

AbstractThe rational design of the electrocatalysts is paramount to alleviating the global energy and environment crisis. Despite a bright future of MnO2 shown in energy storage and conversion, the intrinsic low electrical conductivity glooms its application in electrocatalytic reactions like oxygen reduction/evolution reactions (ORR/OER). The doping strategy is applied to equip the self‐supported MnO2 with enhanced ORR/OER and zinc‐air battery performance. In this work, a class of free‐standing MnO2 nanorods arrays on carbon paper‐doped with either cobalt or nickel cations are engineered through a simple hydrothermal method. The substitutional doping by Co or Ni that partly replaces the Mn ions in the [MnO6] octahedra brings about the Jahn–Teller distortion that exhibits excellent catalytic performance for ORR and OER. Indeed, the ORR performance reveals that the doping resulted in more positive half‐wave potential (by >20 mV), higher limiting current densities, and an electron transfer number close to four. As for the OER, the doping not only decreases the overpotential at 10 mA cm−2 but also brings about an enhancement in the current density at 1.76 V six times greater than with the undoped MnO2 catalyst. An optimal concentration of 0.25 in the molar ratio Co/Mn or Ni/Mn is discovered based on the ORR/OER bifunctionality. Homemade rechargeable Zn–air aqueous batteries assembled with doped MnO2 deliver higher peak power density, higher specific capacity, lower charge voltage, lower charge/discharge voltage, and robust stability.

Metal–organic frameworks-inspired design of highly efficient nitrogen-doped carbon nanoflower electrocatalysts for Zn–air batteries

Metal–organic frameworks-inspired design of highly efficient nitrogen-doped carbon nanoflower electrocatalysts for Zn–air batteries

N,S-Codoped Carbon Nanostructures Encapsulated with FeNi Nanoparticles as a Bifunctional Electrocatalyst for Rechargeable Zn–Air Batteries

The exploration of highly efficient, low-cost, and durable oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional electrocatalysts is extremely desirable but challenging for the practical application of Zn–air batteries. Herein, we report the fabrication of a FeNi alloy nanoparticle (NP)-decorated N,S dual-doped carbon nanocomposite (denoted FeNi/NS-C) as a bifunctional electrocatalyst for Zn–air batteries. The FeNi/NS-C electrocatalyst is produced through the complexation of a N-rich imidazolyl-phenanthroline derivative with metal salts, followed by pyrolysis in the presence of trithiocyanuric acid (TTCA). The FeNi/NS-C electrocatalyst shows comparable ORR activity to that of Pt/C (E1/2 = 0.83 V) and superior OER activity to that of IrO2 (Ej=10 = 1.585 V). The liquid- and solid-state Zn–air batteries assembled with the FeNi/NS-C exhibit high power density and specific capacity. In particular, the FeNi/NS-C-based Zn–air batteries display remarkable durability over 1000 h at 5 mA cm–2 and 70 h at 2 mA cm–2 in liquid and solid electrolytes, respectively. The high performance of the FeNi/NS-C may be related to the synergistic effect of the bimetallic alloy NPs and the N,S dual-doped carbon matrix with a high surface area, porous structure, and unique hybridized morphology.

Facile synthesis of CoPNC-encapsulated Co2P nanoparticles as a bifunctional electrocatalyst for Zn–air batteries

Coupling transition metal phosphide with metal–nitrogen–phosphorus-doped carbon (MPNC) can produce highly active bifunctional electrocatalyst for the rechargeable Zn–air batteries.

A hybridization cage-confinement pyrolysis strategy for ultrasmall Ni3Fe alloy coated with N-doped carbon nanotubes as bifunctional oxygen electrocatalysts for Zn–air batteries

An ultrasmall bifunctional catalyst with excellent ORR and OER properties was achievedviahybridization cage-confinement pyrolysis strategy, and shows a wide prospect for rechargeable Zn–air batteries.

FeCo/N-co-doped 3D carbon nanofibers as efficient bifunctional oxygen electrocatalyst for Zn-air batteries.

Flexible zinc-air batteries (ZABs) are expected to become a promising candidate in energy storage equipment for wearable electronic devices. However, the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have impeded the development of ZABs. Herein, an FeCo- and N-codoped bifunctional electrocatalyst (FeCoNCF) is fabricated by simple one-pot and pyrolysis strategies. Concretely, the bacterial cellulose (BC) and Prussian blue analogue (PBA) derived transition metal and nitrogen doped carbon (M-N-C) composites provide ORR and OER active sites. FeCoNCF exhibits outstanding ORR and OER activities. It displays a favorable high half-wave potential (0.81 V) and a low overpotential at 10 mA cm-2 (341 mV), which are on a par with commercial Pt/C and RuO2, and shows outstanding stability. The sandwich-type flexible zinc-air battery containing FeCoNCF shows a favorable power density (49.29 mW cm-2) and superior cycling stability.

Metal–organic framework-derived Co single atoms anchored on N-doped hierarchically porous carbon as a pH-universal ORR electrocatalyst for Zn–air batteries

Co-SAs/N-C/rGO catalyst with atomic CoN4 moiety manifests exceptional ORR activity in pH-universal media.

Protruding N-doped carbon nanotubes on elongated hexagonal Co–N–C nanoplates as bifunctional oxygen electrocatalysts for Zn–air batteries

A metastable bimetallic ZnCo-ZIF-L topochemical phase conversion and subsequent pyrolysis strategy was developed to fabricate Co–N–C@NCNTs, which exhibit excellent ORR/OER performance with an overpotential gap of 0.748 V.

Single-cell-array biomass-templated architecture of hierarchical porous electrocatalysts for Zn-air and Zn-H2O2 batteries.

Hierarchically macro-meso-microporous ZIF-67/nori-derived electrocatalysts were synthesized by using single-cell-array nori and ZIF-67 as macroporous and microporous templates, and KOH as a meso/micropore-forming reagent. The ZIF-67/nori-800-based Zn-H2O2 battery achieved a high maximum power density, of 476 mW cm-2, and a specific energy density of 964 W h kg-1 at 50 mA cm-2.

Metal-Organic Frameworks (MOFs) Derived Materials Used in Zn-Air Battery.

It is necessary to develop new energy technologies because of serious environmental problems. As one of the most promising electrochemical energy conversion and storage devices, the Zn–air battery has attracted extensive research in recent years due to the advantages of abundant resources, low price, high energy density, and high reduction potential. However, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of Zn–air battery during discharge and charge have complicated multi-electron transfer processes with slow reaction kinetics. It is important to develop efficient and stable oxygen electrocatalysts. At present, single-function catalysts such as Pt/C, RuO2, and IrO2 are regarded as the benchmark catalysts for ORR and OER, respectively. However, the large-scale application of Zn–air battery is limited by the few sources of the precious metal catalysts, as well as their high costs, and poor long-term stability. Therefore, designing bifunctional electrocatalysts with excellent activity and stability using resource-rich non-noble metals is the key to improving ORR/OER reaction kinetics and promoting the commercial application of the Zn–air battery. Metal–organic framework (MOF) is a kind of porous crystal material composed of metal ions/clusters connected by organic ligands, which has the characteristics of adjustable porosity, highly ordered pore structure, low crystal density, and large specific surface area. MOFs and their derivatives show remarkable performance in promoting oxygen reaction, and are a promising candidate material for oxygen electrocatalysts. Herein, this review summarizes the latest progress in advanced MOF-derived materials such as oxygen electrocatalysts in a Zn–air battery. Firstly, the composition and working principle of the Zn–air battery are introduced. Then, the related reaction mechanism of ORR/OER is briefly described. After that, the latest developments in ORR/OER electrocatalysts for Zn–air batteries are introduced in detail from two aspects: (i) non-precious metal catalysts (NPMC) derived from MOF materials, including single transition metals and bimetallic catalysts with Co, Fe, Mn, Cu, etc.; (ii) metal-free catalysts derived from MOF materials, including heteroatom-doped MOF materials and MOF/graphene oxide (GO) composite materials. At the end of the paper, we also put forward the challenges and prospects of designing bifunctional oxygen electrocatalysts with high activity and stability derived from MOF materials for Zn–air battery.