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The electrochemical CO2 reduction reaction (CO2RR) using renewably generated electricity under mild conditions is a promising and sustainable approach to convert CO2 to value-added chemicals. Cu and Cu alloys are considered to be potential catalysts for CO2 reduction among numerous catalysts. Unfortunately, the product selectivity and conversion efficiency during the CO2RR are severely limited by the unavoidable competitive hydrogen evolution reaction (HER). Here, we developed a facile deposition method based on magnetron co-sputtering to optimize the alloy composition of Cu. As a result, we found that CuAg electrode of Sn addition can effectively inhibit the HER during the CO2RR and improve the selectivity of CO, and the FE of CO can reach 93% at −0.85 V. The large lattice distortions and strain effect after Sn addition affect the electronic structure and further result in the downshift of the d-band center, which causes the Gibbs free energy of the formation of *H on the CuAgSn surface to increase dramatically. Although the formation energy barrier of *COOH doesn't decrease after Sn addition, the selectivity of CO is enhanced, owing to the selective suppression of the HER. This work provides an effective way to improve the CO2 reduction performance of binary alloys by adding a small amount of a third metallic element. [ABSTRACT FROM AUTHOR]

Metallic phase molybdenum disulfides exhibit impressive charge transfer ability and this has made them interesting candidates for use in the field of nano-science and heterogeneous catalysis. However, the synthesis of 100% pure bare 1T-MoS2 is difficult due to its kinetic instability. In the past, the phase transition mechanism from a semiconductor (2H) to a metallic (1T) phase has been explained only by theoretical calculations. Herein, we used magnetron sputtering to deposit a series of MoS2 films containing various metal heteroatoms as the dopants. Density functional theory (DFT) calculations revealed that the single-doped Cu-MoS2, Au-MoS2, Ag-MoS2, and Al-MoS2 exhibited distinct phase transitions compared to Cr-MoS2, Hf-MoS2, Ta-MoS2, and Zr-MoS2, due to the introduction of additional charge. Furthermore, the hydrogen evolution reaction (HER) activities of the series of MoS2 films were explored, and the adsorption free energy of H atoms was evaluated by DFT calculations. [ABSTRACT FROM AUTHOR]

Aqueous-based Zn–air and Al–air batteries are considered to be promising post-lithium energy storage technologies owing to their safety, environmental friendliness, affordability, and high energy density. Nevertheless, traditional liquid Zn–air and Al–air batteries have problems such as volatilization and leakage, as well as the realization of miniaturized, portable, and wearable electronic devices. The practice of optimizing the battery structure by replacing the flowing electrolyte with a solid type has emerged and made significant progress in the past ten years. Herein, this review provides a guiding and comprehensive summary of the basic understanding and manufacturing ideas of the solid electrolyte for Zn–air and Al–air batteries. First, two types of alkaline solid electrolytes are distinguished, including alkaline anion exchange membranes (AAEMs) and gel polymer electrolytes (GPEs). Then, three sorts of major framework materials (i.e., artificial organic polymer, biomass materials, and inorganic materials) are reviewed and discussed. Most importantly, the latest research progress and improvement strategies to enhance the electrolyte membrane performances involving conductivity, mechanical properties, and electrochemical stability are also highlighted. Finally, challenges and prospects for the future development of alkaline solid electrolytes are emphasized. [ABSTRACT FROM AUTHOR]

Here we prepare a hexagonal boron nitride (h-BN)–polyethylene oxide composite polymer electrolyte via a convenient casting method, which shows high mechanical strength. Meanwhile, the electrochemical properties (electrochemical window and lithium ion transference number) are enhanced but the ionic conductivity of the h-BN composite electrolyte is decreased after adding h-BN. Density functional theory (DFT) calculation results show that a stronger binding effect is observed between TFSI− and BN, compared to that between Li+ and BN. Molecular dynamics (MD) simulations are also utilized to study the mechanism behind the enhanced Li ion diffusion by h-BN addition. Li+ diffusion in PEO/LiTFSI/BN is lower than that in the PEO/LiTFSI system, but the diffusion of TFSI− exhibits a more significant decline rate in the presence of BN. This indicates that the presence of BN suppresses anion motion and enhances selectivity in Li+ transport. Thus, the PEO/LiTFSI/h-BN composite electrolyte exhibits higher Li ion conductivity but lower anion diffusivity than the PEO/LiTFSI system. Hence the h-BN composite polymer electrolyte in a Li/Li symmetric battery provides a long cycling time of 430 h at 0.2 mA cm−2. A Li metal/LiFePO4 full battery with the PEO/LiTFSI/h-BN composite electrolyte also works more efficiently for long-term cycling (140 cycles) than a filler-free PEO based electrolyte (39 cycles). [ABSTRACT FROM AUTHOR]

Defect and interface engineering is a powerful strategy to tune the electronic structure and adsorption behavior of electrocatalysts, boosting the performance of the electrocatalytic CO2 reduction reaction (eCO2RR). Herein, we construct a hybrid electrocatalyst, Bi2S3–Bi2O3@rGO, with a large amount of defects (oxygen vacancies etc.) and a specific interface between bismuth sulfide (Bi2S3) and bismuth oxide (Bi2O3) by a partial precipitation conversion method. Both experimental results and theoretical calculations reveal that the Bi2S3–Bi2O3 interface drastically lowers the formation energy of HCOO*, in favor of the production of formate (HCOOH) over CO, promoting the conversion of CO2 to HCOOH. The as-prepared electrocatalyst shows excellent electrocatalytic activity to generate HCOOH with a high faradaic efficiency of over 90% and a low overpotential of 700 mV, as well as excellent durability for more than 24 h. [ABSTRACT FROM AUTHOR]

Although NiFe-based (oxy)hydroxides species have been recognized as one of the most promising water oxidation catalysts, existing synthetic methods are difficult to fulfill the requirements of catalytic performance, lifetime and large-scale production. Here, we develop a scaled-up and simple dual-oxidative etching strategy for introducing metallic copper into a NiFe hydroxide nanosheet array on a Ni foam electrode (Cu–NiFe LDH/NF) for the oxygen evolution reaction. This dual-oxidation strategy is achieved via a galvanic–corrosion reaction between the metallic Ni template and ions with higher reduction potential (Fe3+ and Cu2+). The as-prepared electrode exhibits unparalleled activity toward water oxidation with an overpotential of 185 mV at a current density of 10 mA cm−2 and Tafel slope of merely 30 mV dec−1, respectively. More importantly, this inexpensive and simple manufacturing technique affords the Cu–NiFe LDH/NF electrode excellent activity retention for over 1200 hours. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a promising clean and renewable energy source. Thus, efficient and inexpensive electrocatalysts for the HER have attracted considerable attention. Here, we report a two-step method for the synthesis of a unique CoMoO4–Co2Mo3O8 heterostructure. The CoMoO4–Co2Mo3O8 heterostructure exhibited superior HER activity that included a low overpotential of 57 mV, a Tafel slope of 55 mV dec−1 in a 1 M KOH solution, and excellent long-term stability given its high intrinsic activity and superior conductivity. Density functional theory calculations indicated that CoMoO4 and Co2Mo3O8 synergistically optimized electron distribution to reduce hydrogen adsorption energy and significantly enhance electrocatalytic activity. Our work may provide novel ideas for improving the HER performance of valence-rich transition element oxides. [ABSTRACT FROM AUTHOR]

In this study, we report a two dimensional network through the combination of CoO nanoparticles and nitrogen doped carbon nanotubes (CoO-NCNTs) derived from a lamellar coordination polymer, ([CoII(2,3-chedc)(DABCO)0.5]), (2,3-chedc, cyclohexene-2,3-dicarboxylate; DABCO, 1,4-diazabicyclo[2.2.2]octane). During the pyrolysis of this two dimensional metal–organic framework (MOF), the NCNTs emerge accompanied with the catalysis of CoO nanoparticles and are connected to form two dimensional networks. The cobalt oxide particles are encapsulated and remain at the apical position of NCNTs. Due to the specific architecture and high content of CoO in the composite, it possesses great potential for lithium/sodium storage. Noticeably, high capacity and super long calendar life of 2000 cycles with only 0.0063% capacity loss per cycle is acquired for Li storage at a current density of 500 mA g−1. In addition, it also exhibits good sodium storage performance, which delivers a high capacity of 450 mA h g−1, and long cycling capability for 300 cycles with a capacity loss of 0.066% at a rate of 500 mA g−1. Remarkable performance emphasizes the great potential of the two dimensional MOFs for extensive utilizations in energy storage and transfer processes. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is considered to be one of the most promising strategies to produce hydrogen to ease the energy crisis. In this study, we demonstrate a galvanic-replacement mediated synthesis of copper-nickel bimetallic nitrides on partially sacrificial nickel foams (CuxNi4−xN/NF) as the direct catalytic electrode for hydrogen evolution reaction (HER). The Ni foam serves as not only the cathodic electrode substrate, but also the only Ni precursor for the CuxNi4−xN catalyst, which can be galvanically replaced by Cu(i) ion. The obtained CuxNi4−xN/NF exhibits an excellent electrocatalytic performance towards the HER in both acidic and alkaline media with a very low overpotential of ∼110 mV at a current density of 100 mA cm−2 in the 0.5 M H2SO4 and 1 M KOH solutions. The electrode presents a good long-term working stability, particularly reflecting in more than 65 h of consistent galvanostatic electrolysis in 0.5 M H2SO4. The CuNi bimetallic nitrides are intrinsically metallic, allowing for an enhanced charge transport and an excellent electrical conductivity. Combining the experimental result and the theoretical calculation further reveals that the electrocatalytic active sites primarily originate from nickel species. [ABSTRACT FROM AUTHOR]

Carbon-based anode materials are faced with challenges in rechargeable sodium-ion batteries (SIBs). In this paper, we describe a substrate, N-doped amorphous micron-sized carbon ribbons (AMCRs), derived from biomass from raupo, on which few-layer MoS2 nanosheets with enlarged interlayer spacings (≈0.75 nm) are anchored. The nitrogen-enriched AMCRs are economically prepared by a single pyrolysis step. The uniform distribution of nitrogen atoms enables ultra homogeneous growth of the MoS2 nanosheets on the AMCRs. The as-prepared AMCRs@MoS2 composite is fabricated as an anode material for SIBs, and carboxymethylcellulose (CMC) and polyvinylidene fluoride (PVDF) are chosen as binders to mix the anode materials to compare their battery performance. The anode composite with CMC as the binder demonstrates an improved initial coulombic efficiency of 75.6%, a higher specific capacity (366 mA h g−1 at a current density of 1 A g−1) and a better cycling stability (305 mA h g−1 after 300 cycles). The anode material composed of few-layer MoS2 anchored on low-cost nitrogen-doped AMCRs with CMC as the binder can be a competing candidate for large-scale SIB production. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a step-wise route to build a novel one-dimensional (1D) architecture formed by MoS2 nanosheets and amorphous carbon nanotubes (ACNTs). Being evaluated as an anode material for NIBs, the as-prepared MoS2@ACNT electrode is capable of exhibiting a remarkable reversible capacity of 461 mA h g−1 at a current density of 500 mA g−1 over 150 cycles. Moreover, the coulombic efficiency is almost up to 100% except for the initial few cycles during the whole cycling test. The smart electrode architecture and appropriate synergistic effect between MoS2 and ACNTs are probably responsible for the enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

In this paper, we report a facile approach to the synthesis of one-dimension (1D) hierarchical NiCoO2 nanosheets (NSs)@amorphous CNT composites based on the templates and carbon source of polymeric nanotubes (PNTs). Importantly, these sulfonated PNTs can also be used to prepare many other functional 1D metal oxides@amorphous CNT nanostructures, such as TiO2, SnO2, CoO and NiO, etc. Due to the outstanding nanostructures and the synergistic effects of the NiCoO2 NSs and amorphous CNTs, an ultrahigh discharge capacity of 1309 mA h g-1 is delivered by the NiCoO2@CNT composites, even after 300 cycles at a current density of 400 mA g-1. The favorable improvements of the NiCoO2 based lithium-ion batteries (LIBs) reported in this work illustrate that the 1D amorphous carbon matrix offers significant benefits for high-capacity metal oxide anode nanomaterials. [ABSTRACT FROM AUTHOR]

A novel one-dimensional (1-D) caterpillar-like manganese dioxide–carbon (MnO2–C) nanocomposite has been synthesized by a direct redox reaction between carbon nanotubes (CNTs) and permanganate ions for the first time. The as-prepared nanostructured MnO2–C composite mainly consisting of -MnO2nanoflakes had a unique microstructure, high specific surface area (200 m2g−1) and favourable conductivity. The nanostructured MnO2–C composite, added as a modification to the glassy carbon (GC) electrode viaa direct electrochemical co-deposition process with a chitosan hydrogel, was found to exhibit excellent catalytic activity toward l-cysteine electro-oxidation because the specific interaction between the –SH group of l-cysteine and solid MnO2occurred to form surface complexes. A determination of l-cysteine at the MnO2–C/chitosan/GC (MnO2–C/chit/GC) electrode was carried out by amperometric measurement. Under the optimum experimental conditions, the detection response for l-cysteine was fast (within 7 s). The logarithm of catalytic currents shows a good linear relationship with that of the l-cysteine concentration in the range of 0.5–680 μM (R= 0.9986), with a low detection limit of 22 nM. The MnO2–C/Chit/GC electrode exhibited excellent stability (without any decrease of the response signal after 1 month) and admirable resistance against interference like glutathione and other oxidizable amino acids (tryptophan, tyrosine, l-lysine and methionine). [ABSTRACT FROM AUTHOR]