The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

To date, copper is the only heterogeneous catalyst that has shown a propensity to produce valuable hydrocarbons and alcohols, such as ethylene and ethanol, from electrochemical CO2 reduction (CO2R). There are variety of factors that impact CO2R activity and selectivity, including the catalyst surface structure, morphology, composition, the choice of electrolyte ions and pH, and the electrochemical cell design. Many of these factors are often intertwined, which can complicate catalyst discovery and design efforts. Here we take a broad and historical view of these different aspects and their complex interplay in CO2R catalysis on Cu, with the purpose of providing new insights, critical evaluations, and guidance to the field with regard to research directions and best practices. First, we describe the various experimental probes and complementary theoretical methods that have been used to discern the mechanisms by which products are formed, and next we present our current understanding of the complex reaction networks for CO2R on Cu. We then analyze two key methods that have been used in attempts to alter the activity and selectivity of Cu: nanostructuring and the formation of bimetallic electrodes. Finally, we offer some perspectives on the future outlook for electrochemical CO2R.

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Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte

This article provides an up-to-date perspective on the use of anion-exchange membranes in fuel cells, electrolysers, redox flow batteries, reverse electrodialysis cells, and bioelectrochemical systems (e.g. microbial fuel cells). The aim is to highlight key concepts, misconceptions, the current state-of-the-art, technological and scientific limitations, and the future challenges (research priorities) related to the use of anion-exchange membranes in these energy technologies. All the references that the authors deemed relevant, and were available on the web by the manuscript submission date (30th April 2014), are included.

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Anion-exchange membranes in electrochemical energy systems

Active and stable electrocatalysts made from earth-abundant elements are key to water splitting for hydrogen production through electrolysis. The growth of NiSe nanowire film on nickel foam (NiSe/NF) insitu by hydrothermal treatment of NF using NaHSe as Se source is presented. When used as a 3D oxygen evolution electrode, the NiSe/NF exhibits high activity with an overpotential of 270mV required to achieve 20mAcm(-2) and strong durability in 1.0M KOH, and the NiOOH species formed at the NiSe surface serves as the actual catalytic site. The system is also highly efficient for catalyzing the hydrogen evolution reaction in basic media. This bifunctional electrode enables a high-performance alkaline water electrolyzer with 10mAcm(-2) at a cell voltage of 1.63V.

NiSe Nanowire Film Supported on Nickel Foam: An Efficient and Stable 3D Bifunctional Electrode for Full Water Splitting

Increasing energy demands and environment awareness have promoted extensive research on the development of alternative energy conversion and storage technologies with high efficiency and environmental friendliness. Among them, water splitting is very appealing, and is receiving more and more attention. The critical challenge of this renewable-energy technology is to expedite the oxygen evolution reaction (OER) because of its slow kinetics and large overpotential. Therefore, developing efficient electrocatalysts with high catalytic activities is of great importance for high-performance water splitting. In the past few years, much effort has been devoted to the development of alternative OER electrocatalysts based on transition-metal elements that are low-cost, highly efficient, and have excellent stability. Here, recent progress on the design, synthesis, and application of OER electrocatalysts based on transition-metal elements, including Co, Ni, and Fe, is summarized, and some invigorating perspectives on the future developments are provided.

Transition-Metal (Co, Ni, and Fe)-Based Electrocatalysts for the Water Oxidation Reaction

The long-standing issue of Li-dendrite formation and growth during repeated plating or stripping processes prevents the practical application of Li-metal anodes for high-specific-energy batteries. Here we develop an approach to control dendrite growth by coating the separator with functionalized nanocarbon (FNC) with immobilized Li ions. During cycling, the Li dendrites grow toward each other simultaneously from both the FNC layer on the separator and the Li-metal anode; when the dendrites meet, the growth changes direction: rather than penetrating the separator, a dense Li layer is formed between the separator and the Li anode. This controlled growth alleviates the solid electrolyte interphase formation, reduces the decomposition of the electrolyte, and improves the cyclability of the Li-metal cell. In a Li/LiFePO4 coin cell with three different electrolytes, we show that this approach enables a long stable cycle life (>800 cycles with 80% retention of the initial capacity) and improved efficiency (>97%). Our method offers promise for application in practical Li-metal batteries, and it may also be useful for tackling dendrite issues for other metals. Li-dendrite growth is an inherent problem for the application of Li-metal anodes in batteries. Here the authors coat the separator with functionalized nanocarbon with immobilized Li ions, regulating the dendrite growth direction and thereby improving the battery performance.

Making Li-metal electrodes rechargeable by controlling the dendrite growth direction

Pd-Ni electrocatalysts for efficient ethanol oxidation reaction in alkaline electrolyte

Activities of Cu nanoparticles supported on carbon black (VC), single-wall carbon nanotubes (SWNTs), and Ketjen Black (KB) toward CO2 electroreduction to hydrocarbons (CH4, C2H2, C2H4, and C2H6) are evaluated using a sealed rotating disk electrode (RDE) setup coupled to a gas chromatograph (GC). Thin films of supported Cu catalysts are deposited on RDE tips following a procedure well-established in the fuel cell community. Lead (Pb) underpotential deposition (UPD) is used to determine the electrochemical surface area (ECSA) of thin films of 40 wt % Cu/VC, 20 wt % Cu/SWNT, 50 wt % Cu/KB, and commercial 20 wt % Cu/VC catalysts on glassy carbon electrodes. Faradaic efficiencies of four carbon-supported Cu catalysts toward CO2 electroreduction to hydrocarbons are compared to that of electrodeposited smooth Cu films. For all the catalysts studied, the only hydrocarbons detected by GC are CH4 and C2H4. The Cu nanoparticles are found to be more active toward C2H4 generation versus electrodeposited smooth copper ...

CO2 Electroreduction to Hydrocarbons on Carbon-Supported Cu Nanoparticles

The electrocatalytic oxygen evolution reaction (OER) is a critical anode reaction often coupled with electron or photoelectron CO2 reduction and H2 evolution reactions at the cathode for renewable energy conversion and storage. However, the sluggish OER kinetics and the utilization of precious metal catalysts are key obstacles in the broad deployment of these energy technologies. Herein, inexpensive supported 4 nm Ni–Fe nanoparticles (NiyFe1–yOx/C) featuring amorphous structures have been prepared via a solution-phase nanocapsule method for active and durable OER electrocatalysts in alkaline electrolyte. The Ni–Fe nanoparticle catalyst containing 31% Fe (Ni0.69Fe0.31Ox/C) shows the highest activity, exhibiting a 280 mV overpotential at 10 mA cm–2 (equivalent to 10% efficiency of solar-to-fuel conversion) and a Tafel slope of 30 mV dec–1 in 1.0 M KOH solution. The achieved OER activity outperforms NiOx/C and commercial Ir/C catalysts and is close to the highest performance of crystalline Ni–Fe thin films r...

Le Xin

Papers

Making Li-metal electrodes rechargeable by controlling the dendrite growth direction

Pd-Ni electrocatalysts for efficient ethanol oxidation reaction in alkaline electrolyte

CO2 Electroreduction to Hydrocarbons on Carbon-Supported Cu Nanoparticles

Electrocatalytic Oxygen Evolution over Supported Small Amorphous Ni–Fe Nanoparticles in Alkaline Electrolyte

Electrocatalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid on supported Au and Pd bimetallic nanoparticles