Small Charge-discharge Voltage Gap Research Articles

FeNi-LDH COATED WITH ORANGE-PEEL CARBON AEROGEL FOR OXYGEN EVOLUTION REACTION.

In this work, the waste orange-peel was used as carbon source, and the orange-peel derived carbon material can be obtained through simple pyrolysis. Then, we designed the structure of orange-peel carbon aerogel grown on iron-nickel layered double hydroxides in situ to achieve the effect of carbon coating (FeNi-LDH/CA). The oxygen evolution reaction catalytic performance of FeNi-LDH/CA is excellent, far exceeding that of commercial RuO2. In 1 M KOH, the overpotential of FeNi-LDH/CA is only 250 mV (10 mA cm-2), obviously better than that of commercial RuO2 (295 mV). FeNi-LDH/CA shows good cycling stability, and after long-term i-t testing, the performance only decays by 3% after running at 100 mA cm-2 for 100 h. When used as an anode, the voltage of water-splitting is only 1.48 V at 10 mA cm-2. The rechargeable liquid zinc-air battery based on Pt/C-FeNi-LDH/CA catalyst has higher open-circuit voltage (1.543 V) and galvanostatic discharge capacity at 1.23 V (830 min, 10 mA cm-2). Moreover, the zinc-air battery based on Pt/C-FeNi-LDH/CA has a small charge-discharge voltage gap (0.65 V) at 10 mA cm-2, after 200 consecutive cycles (66 h), the charge-discharge voltage gap only increased by about 30 mV, indicating good cycling stability.

3D coordination polymer derived CoNi@GO as a highly efficient OER/ORR bifunctional catalyst for Zn-air rechargeable batteries

Developing highly active and durable non-noble metal based bifunctional electrocatalysts is still a key step for rechargeable metal-air batteries. In the current work, a new three-dimensional cyanide-bridged CoNi complex {{[Ni(pn)2]3[Co(CN)6]2}·3H2O}n (pn = 1, 3-diaminopropane) was synthesized and characterized. And a bifunctional electrocatalyst CoNi@GO for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) was prepared by pyrolyzing process with graphene oxide (GO) as template and CoNi complex as precursor. Density functional theory calculations revealed that the nanostructured CoNi alloy embedded in the lamellar porous GO and there was strong synergistic coupling between the carbon based material and CoNi alloy. The as-obtained catalyst showed the outstanding electrocatalytic activity and the excellent potential difference between ORR and OER is 0.697 V versus Pt/C+RuO2 (0.708 V). The Zinc-air battery prepared with CoNi@GO as an air electrode has a small charge-discharge voltage gap of 0.91 V, a high energy efficiency of 59.5%, and could be cycled stably for more than 240 h at 10 mA cm−2. This work confirmed the feasibility of developing coordination polymer (CP) based non-noble metal bi-functional electrocatalysts for energy storage and conversion, and provided a valuable strategy for the rational design of new non-noble metal electrocatalysts in future.

Nitrogen-doped NiCo2O4 nanowires on carbon paper as a self-supported air cathode for rechargeable Zn-air batteries

A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a facile strategy to fabricate nitrogen-doped NiCo2O4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo2O4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts.

Ultra-high voltage efficiency rechargeable zinc-air battery based on high-performance structurally regulated metal-rich nickel phosphides and carbon hybrids bifunctional electrocatalysts

Metal phosphides featuring electronic structure similar to Pt-group metal have triggered substantial concerns, and unveiling active species is crucial to rational design of bifunctional catalysts for ORR and OER. Herein, a hybrid of metal-rich nickel phosphides strongly coupled with heteroatom-doped carbon (NixP-NP-C) is constructed by a facile pyrolysis combined with in-situ phosphorization of MOFs. This unique hybrid exhibits superior electrocatalytic activity and stability toward ORR and OER demonstrated by delightful high Eonset and E1/2 up to 0.90 and 0.76 V, respectively, along with a long-term stability. The resulting zinc-air battery shows an impressively small charge-discharge voltage gap and delivers a high power density of 266 mW cm−2. The high catalytic performance of NixP-NP-C can be ascribed to synergistic effect of metal-rich Ni2P actives and heteroatoms doped porous carbon. Consequently, hybrid of carbon and metal phosphides may provide a meaningful reference for developing high performance oxygen catalysts in metal-air battery.

Significantly boosted oxygen electrocatalysis with cooperation between cobalt and iron porphyrins.

Developing electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is of great importance. Herein, Co tetrakis(pentafluorophenyl)porphyrin (Co-P) and Fe chloride tetrakis(pentafluorophenyl)porphyrin (Fe-P) were loaded on carbon nanotubes (CNTs) for combining the electrocatalytic advantages of both Co-P and Fe-P. The resultant (Co-P)0.5(Fe-P)0.5@CNT composite displayed significantly boosted activity for the selective four-electron ORR with a half-wave potential of 0.80 V versus reversible hydrogen electrode (RHE) and for the OER with a potential of 1.65 V versus RHE to obtain 10 mA cm-2 current density in 0.1 M KOH. A Zn-air battery assembled from (Co-P)0.5(Fe-P)0.5@CNT exhibited a small charge-discharge voltage gap of 0.74 V at 2 mA cm-2, a high power density of 174.5 mW cm-2 and a good rechargeable stability (>120 cycles).

Multi-dimensional hierarchical CoS2@MXene as trifunctional electrocatalysts for zinc-air batteries and overall water splitting

The demanding all-in-one electrocatalyst system for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in zinc-air batteries or water splitting requires elaborate material manufacturing, which is usually complicated and time-consuming. Efficient interface engineering between MXene and highly active electrocatalytic species (CoS2) is, herein, achieved by an in situ hydrothermal growth and facile sulfurization process. The CoS2@MXene electrocatalyst is composed by one-dimensional CoS2 nanowires and two-dimensional MXene nanosheets, which lead to a hierarchical structure (large specific surface area and abundant active sites), a spatial electron redistribution (high intrinsic activity), and high anchoring strength (superior performance stability). Therefore, the electrocatalyst achieves enhanced catalytic activity and long-time stability for ORR (a half-wave potential of 0.80 V), OER (an overpotential of 270 mV at 10 mA cm−2, i.e., η10 = 270 mV) and HER (η10 = 175 mV). Furthermore, the asymmetry water splitting system based on the CoS2@MXene composites delivers a low overall voltage of 1.63 V at 10 mA cm−2. The solid-state zinc-air batteries using CoS2@MXene as the air cathode display a small charge-discharge voltage gap (0.53 V at 1 mA cm−2) and superior stability (60 circles and 20-h continuous test). The energy interconversion between the chemical energy and electricity can be achieved by a self-powered system via integrating the water splitting system and quasi-solid-state zinc-air batteries. Supported by in situ Raman analyses, the formation of cobalt oxyhydroxide species provides the active sites for water oxidation. This study paves a promising avenue for the design and application of multifunctional nanocatalysts.

One-dimensional Mn3O4/NiCo2S4 nanocomposites as high-performance bifunctional electrocatalyst for rechargeable liquid/flexible Zn-air batteries

Rational design of bifunctional oxygen catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with high efficiency and low-cost are significantly in the development of rechargeable Zn-air batteries (ZABs). Herein, it is designed one-dimensional rod-like Mn3O4/NiCo2S4 nanostructure. The inner Mn3O4 nanorod and the outer coating of the NiCo2S4 layers make the composite material have a stable structure, thus exhibiting a rather high bifunctional catalytic activity (ΔE = 0.74 V) and long-term durability toward ORR/OER. An interlaced region is formed at the interface of the dual phases by the Kirkendall effect, where Mn3O4/NiCo2S4 nanocrystals, oxygen vacancies and defects co-exist. The Mn3O4/NiCo2S4 exhibits an onset potential of 0.92 V and a half-wave potential of 0.81 V, and the OER potential is only 1.55 V at 10 mA cm−2. When using this catalyst in rechargeable ZABs, the batteries show a high power density (106.26 mW cm−2), superior rate stability, small charge-discharge voltage gap (0.86 V) and long-term cycles (650 cycles over 216 h at 5 mA cm−2). The flexible ZABs exhibit a high open-circuit voltage of 1.427 V and stably cycled 50 cycles (16.8 h) with a small charge-discharge voltage gap (0.5 V) at 1 mA cm−2.

NiFe nanoparticles embedded N-doped carbon nanotubes as high-efficient electrocatalysts for wearable solid-state Zn-air batteries

Wearable and rechargeable Zn-air batteries (ZABs) hold great potential application in flexible electronic devices, and light-weight power sources for their high energy density and good safety. However, the practical application of ZABs is hindered by their low power density and poor rechargeability, which arises from the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on air cathode. Herein, a high-power, wearable ZAB with impressive electrochemical performances is achieved based on a new NiFe nanoparticles embedded N-doped carbon nanotubes (NiFe/N-CNT) as bifunctional electrocatalyst. The in-situ Raman and oxygen adsorption and DFT calculations reveal that our designed NiFe/N-CNT catalyst can remarkably promote the oxygen adsorption in ORR and OH− adsorption in OER, which enable this NiFe/N-CNT to own superior electrocatalytic activity toward both OER and ORR. The as-fabricated wearable ZAB with the NiFe/N-CNT as air cathode exhibits an ultrahigh open-circuit potential (Voc) of 1.41 V and a remarkable high peak power density of 105.4 mW cm−2, Furthermore, it also obtains a small charge-discharge voltage gap of 0.61 V and superior durability for 800 min. This research provides a new design pathway for the electrocatalysts for high-performance rechargeable and wearable metal-air batteries.

Molecular Engineering of a 3D Self-Supported Electrode for Oxygen Electrocatalysis in Neutral Media.

Electrodes for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are required in energy conversion and storage technologies. An assembly strategy involves covalently grafting Co corrole 1 onto Fe3 O4 nanoarrays grown on Ti mesh. The resulted electrode shows significantly improved activity and durability for OER and ORR in neutral media as compared to Fe3 O4 alone and with directly adsorbed 1. It also displays higher atom efficiency (at least two magnitudes larger turnover frequency) than reported electrodes. Using this electrode in a neutral Zn-air battery, a small charge-discharge voltage gap of 1.19 V, large peak power density of 90.4 mW cm-2 , and high rechargeable stability for >100 h are achieved, opening a promising avenue of molecular electrocatalysis in a metal-air battery. This work shows a molecule-engineered electrode for electrocatalysis and demonstrates their potential applications in energy conversion and storage.

FeNi alloys encapsulated in N-doped CNTs-tangled porous carbon fibers as highly efficient and durable bifunctional oxygen electrocatalyst for rechargeable zinc-air battery

It remains a great challenge to develop high-efficient, low-cost and robustly stable bifunctional oxygen electrocatalysts for rechargeable metal-air batteries. Herein, we report a promising electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrocatalysts are composed of nanostructured FeNi alloy nanoparticles inlaid on N-doped carbon nanotubes (CNTs)-tangled porous carbon fibers (FeNi/N-CPCF). Benefiting from its hierarchically porous structures with bamboo-like CNTs grafted, and strong synergetic coupling between FeNi alloys and N-doped carbon species, the as-prepared FeNi/N-CPCF-950 demonstrates a half-wave potential of 0.867 V for ORR and a low operating potential of 1.585 V at 10 mA cm−2 for OER in 0.1 M KOH, outperforming commercial Pt/C and RuO2. Moreover, such bifunctioal catalyst endows the homemade zinc-air batteries with a high energy efficiency of 61.5%, small charge-discharge voltage gap of 0.764 V, and outstanding cycling performance (640 h, 960 cycles) at 10 mA cm−2 under ambient conditions.

Co Nanoislands Rooted on Co-N-C Nanosheets as Efficient Oxygen Electrocatalyst for Zn-Air Batteries.

Developing non-precious-metal bifunctional oxygen reduction and evolution reaction (ORR/OER) catalysts is a major task for promoting the reaction efficiency of Zn-air batteries. Co-based catalysts have been regarded as promising ORR and OER catalysts owing to the multivalence characteristic of cobalt element. Herein, the synthesis of Co nanoislands rooted on Co-N-C nanosheets supported by carbon felts (Co/Co-N-C) is reported. Co nanosheets rooted on the carbon felt derived from electrodeposition are applied as the self-template and cobalt source. The synergistic effect of metal Co islands with OER activity and Co-N-C nanosheets with superior ORR performance leads to good bifuctional catalytic performances. Wavelet transform extended X-ray absorption fine spectroscopy and X-ray photoelectron spectroscopy certify the formation of Co (mainly Co0 ) and the Co-N-C (mainly Co2+ and Co3+ ) structure. As the air-cathode, the assembled aqueous Zn-air battery exhibits a small charge-discharge voltage gap (0.82 V@10 mA cm-2 ) and high power density of 132 mW cm-2 , outperforming the commercial Pt/C catalyst. Additionally, the cable flexible rechargeable Zn-air battery exhibits excellent bendable and durability. Density functional theory calculation is combined with operando X-ray absorption spectroscopy to further elucidate the active sites of oxygen reactions at the Co/Co-N-C cathode in Zn-air battery.

In-situ reduction synthesis of La2O3/NiM-NCNTs (M = Fe, Co) as efficient bifunctional electrocatalysts for oxygen reduction and evolution reactions

Highly active and stable bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a vital role in rechargeable zinc-air batteries. In this work, La2O3 and alloy nanoparticles (NiFe and NiCo) decorated nitrogen doped carbon nanotubes hybrids (denoted as La2O3/NiFe-NCNTs and La2O3/NiCo-NCNTs) were successfully prepared by the in-situ reduction procedure. The crystalline structure and morphology of hybrids were characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). La2O3/NiFe-NCNTs revealed desirable bifunctional catalytic activities towards both oxygen reduction reaction (5.1 mA cm−2 at 0.3 V vs. RHE) and oxygen evolution reaction (1.69 V vs. RHE at 10 mA cm−2) in alkaline media. Furthermore, rechargeable zinc-air batteries fabricated with La2O3/NiFe-NCNTs as the bifunctional catalyst demonstrated a small charge-discharge voltage gap (1.04 V) and long-term stability after charge-discharge cycling for 100 cycles.

A novel rechargeable hybrid Na-seawater flow battery using bifunctional electrocatalytic carbon sponge as cathode current collector

A novel rechargeable hybrid Na-seawater flow battery, using natural seawater as an abundant source of active materials, have been developed recently. In this kind of metal-air battery, electrochemical oxygen evolution and reduction are the two key processes taking place during charging and discharging, respectively. In general, powder form of electrocatalysts are attached to the current collectors by using inactive and insulating polymer binders, which inevitably impede the overall performance, and increase the manufacturing costs of the battery. Therefore, a simple way to construct the 3D current collector combined with efficient electrocatalytic activities remains a big challenge. In this work, a 3D macroporous carbon sponge is prepared by the direct carbonization of commercially available polymer “Magic Eraser”. The obtained carbon sponge has interconnected macroporous open 3D scaffold structure and exhibits good flexibility and tailorability. The 3D macroporous carbon sponge shows good bifunctional electrocatalytic activities toward oxygen evolution and reduction reactions in seawater. The fabricated hybrid Na-seawater flow battery using 3D macroporous carbon sponge as cathode current collector displays small charge-discharge voltage gap with high voltage efficiency, excellent rechargeability, and long-term cycling stability.

A novel composite (FMC) to serve as a durable 3D-clam-shaped bifunctional cathode catalyst for both primary and rechargeable zinc-air batteries

Novel and highly durable air cathode electrocatalyst with three dimensional (3D)-clam-shaped structure, MnO2 nanotubes-supported Fe2O3 (Fe2O3/MnO2) composited by carbon nanotubes (CNTs) ((Fe2O3/MnO2)3/4-(CNTs)1/4) is synthesized using a facile hydrothermal process and a following direct heat-treatment in the air. The morphology and composition of this catalyst are analyzed using scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The morphology characteristics reveal that flower-like Fe2O3 particles are highly dispersed on both MnO2 nanotubes and CNT surfaces, coupling all three components firmly. Electrochemical measurements indicate that the synergy of catalyst exhibit superior bi-functional catalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as well as stability than Pt/C and IrO2 catalysts. Using these catalysts for air-cathodes, both primary and rechargeable zinc-air batteries (ZABs) are assembled for performance validation. In a primary ZAB, this 3D-clamed catalyst shows a decent open circuit voltage (OCV, ∼1.48V) and a high discharge peak power density (349mWcm−2), corresponding to a coulombic efficiency of 92%. In a rechargeable ZABs with this bifunctional catalyst, high OCV (>1.3V) and small charge-discharge voltage gap (<1.1V) are achieved along with high specific capacity (780mAhg−1 at 30mAcm−2) and robust cycle-life (1,390 cycles at cycle profile of 20mA/10min).

3D hollow sphere Co3O4/MnO2-CNTs: Its high-performance bi-functional cathode catalysis and application in rechargeable zinc-air battery

There has been a continuous need for high active, excellently durable and low-cost electrocatalysts for rechargeable zinc-air batteries. Among many low-cost metal based candidates, transition metal oxides with the CNTs composite have gained increasing attention. In this paper, the 3-D hollow sphere MnO2 nanotube-supported Co3O4 nanoparticles and its carbon nanotubes hybrid material (Co3O4/MnO2-CNTs) have been synthesized via a simple co-precipitation method combined with post-heat treatment. The morphology and composition of the catalysts are thoroughly analyzed through SEM, TEM, TEM-mapping, XRD, EDX and XPS. In comparison with the commercial 20% Pt/C, Co3O4/MnO2, bare MnO2 nanotubes and CNTs, the hybrid Co3O4/MnO2-CNTs-350 exhibits perfect bi-functional catalytic activity toward oxygen reduction reaction and oxygen evolution reaction under alkaline condition (0.1 M KOH). Therefore, high cell performances are achieved which result in an appropriate open circuit voltage (∼1.47 V), a high discharge peak power density (340 mW cm−2) and a large specific capacity (775 mAh g−1 at 10 mA cm−2) for the primary Zn-air battery, a small charge–discharge voltage gap and a high cycle-life (504 cycles at 10 mA cm−2 with 10 min per cycle) for the rechargeable Zn-air battery. In particular, the simple synthesis method is suitable for a large-scale production of this bifunctional material due to a green, cost effective and readily available process.

Co(II)1-xCo(0)x/3Mn(III)2x/3S Nanoparticles Supported on B/N-Codoped Mesoporous Nanocarbon as a Bifunctional Electrocatalyst of Oxygen Reduction/Evolution for High-Performance Zinc-Air Batteries.

Rechargeable Zn-air battery is an ideal type of energy storage device due to its high energy and power density, high safety, and economic viability. Its large-scale application rests upon the availability of active, durable, low-cost electrocatalysts for the oxygen reduction reaction (ORR) in the discharge process and oxygen evolution reaction (OER) in the charge process. Herein we developed a novel ORR/OER bifunctional electrocatalyst for rechargeable Zn-air batteries based on the codoping and hybridization strategies. The B/N-codoped mesoporous nanocarbon supported Co(II)1-xCo(0)x/3Mn(III)2x/3S nanoparticles exhibit a superior OER performance compared to that of IrO2 catalyst and comparable Zn-air battery performance to that of the Pt-based battery. The rechargeable Zn-air battery shows high discharge peak power density (over 250 mW cm(-2)) and current density (180 mA cm(-2) at 1 V), specific capacity (∼550 mAh g(-1)), small charge-discharge voltage gap of ∼0.72 V at 20 mA cm(-2) and even higher stability than the Pt-based battery. The advanced performance of the bifunctional catalysts highlights the beneficial role of the simultaneous formation of Mn(III) and Co(0) as well as the dispersed hybridization with the codoped nanocarbon support.