High selective electrocatalytic reduction of carbon dioxide to ethylene enabled by regulating the microenvironment over Cu-Ag nanowires.

Copper-based tandem catalysts are effective candidates for yielding multi-carbon (C2+) products in electrochemical reduction of carbon dioxide (CO2RR). However, these catalysts still face a significant challenge regarding in the low selectivity for the production of a specific product. In this study, we report a high selectivity of 77.8 %±2 % at -1.0 V (vs RHE) for the production of C2H4 by using a Cu88Ag12NW catalyst which is primarily prepared through a combined Cu-Ag co-deposition and wet chemical method, employing an attractive strategy focused on regulating the microenvironment over Cu-Ag nanowires. The experimental and computational studies show that the higher *CO coverage and lower intermediate adsorption energy are important reasons for achieving the high C2H4 selectivity of Cu88Ag12NW catalyst. Comsol simulation results indicate that dense nanowires exhibit a nano-limiting effect on OH- ions, thereby leading to an increase in local pH and promoting coupling reactions. The catalyst demonstrates no noticeable decrease in current density or selectivity even after 12 h of continuous operation. The Cu-Ag nanowire composite exhibits remarkable catalytic activity, superior faradaic efficiency, excellent stability, and easy synthesis, which highlights its significant potential for electro-reducing carbon dioxide into valuable products.

Experimental and Theoretical Study of the New Leveler Basic Blue 1 during Copper Superconformal Growth.

A novel chlorinated functional group-modified triphenylmethane derivative leveler BB1 is used to achieve superconformal electrodeposition in microvias. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are performed to study the suppressing effect of BB1, while the convection-dependent adsorption of BB1 on the copper surface is analyzed by galvanostatic measurement, and a BB1 concentration window between 100 and 200 mg/L is beneficial for superfilling. The interactions among BB1, bis-(sodium sulfopropyl) disulfide (SPS), and poly(ethylene glycol) (PEG) are also investigated. Density functional theory (DFT) calculation and in situ Raman spectroscopy are coupled to study the suppression mechanism and synergistic suppression mechanism, namely, the adsorption effect between BB1 and copper substrate, as well as the coordination effect between the modified chlorinated functional group and Cu2+, is proposed. The copper layer becomes smoother and more compact with an increase in BB1 concentration, according to scanning electron microscopy (SEM) and atomic force microscopy (AFM), while X-ray diffraction (XRD) analysis shows that the introduction of BB1 is conducive to the formation of the copper (220) plane. Besides, the solution wettability is boosted by BB1. A copper interconnecting layer with high quality is achieved with 150 mg/L BB1, while the surface deposition thickness (SDT) is about 34 µm and filling percentages (FPs) for microvias with diameters of 100, 125, and 150 µm are 81.34, 82.72, and 81.39%, respectively.

N-Doping Induced Lattice Expansion of 1D Template Confined Ultrathin MoS2 Sheets to Significantly Enhance Lithium Polysulfides Redox Kinetics for Li-S Battery.

Preparing MoS2 -based materials with reasonable structure and catalytic activity to enhance the sluggish kinetics of lithium polysulfides (LiPSs) conversion is of great significance for Li-S batteries (LSBs) but still remain a challenge. Hence, hollow nanotubes composed of N-doped ultrathin MoS2 nanosheets (N-MoS2 NHTs) are fabricated as efficient S hosts for LSBs by using CdS nanorods as a sacrifice template. Characterization and theoretical results show that the template effectively inhibits the excessive growth of MoS2 sheets, and N doping expands the interlayer spacing and modulates the electronic structure, thus accelerating the mass/electron transfer and enhancing the LiPSs adsorption and transformation. Benefiting from the merits, the N-MoS2 NHTs@S cathode exhibits an excellent initial capacity of 887.8 mAh g-1 and stable cycling performances with capacity fading of only 0.0436% per cycle at 1.0 C (500 cycles). Moreover, even at high S loading that of 7.5 mg cm-2 , the N-MoS2 NHTs@S cathode also presents initial excellent areal capacity of 7.80 mAh cm-2 at 0.2 C. This study offers feasible guidance for designing advanced MoS2 -based cathode materials in LSBs.

Key Roles of Interfacial OH- ion Distribution on Proton Coupled Electron Transfer Kinetics Toward Urea Oxidation Reaction.

Enhancing alkaline urea oxidation reaction (UOR) activity is essential to upgrade renewable electrolysis systems. As a core step of UOR, proton-coupled electron transfer (PCET) determines the overall performance, and accelerating its kinetic remains a challenge. In this work, a newly raised electrocatalyst of NiCoMoCuOx Hy with derived multi-metal co-doping (oxy)hydroxide species during electrochemical oxidation states is reported, which ensures considerable alkaline UOR activity (10/500 mA cm-2 at 1.32/1.52 V vs RHE, respectively). Impressively, comprehensive studies elucidate the correlation between the electrode-electrolyte interfacial microenvironment and the electrocatalytic urea oxidation behavior. Specifically, NiCoMoCuOx Hy featured with dendritic nanostructure creates a strengthened electric field distribution. This structural factor prompts the local OH- enrichment in electrical double layer (EDL), so that the dehydrogenative oxidation of the catalyst is directly reinforced to facilitate the subsequent PCET kinetics of nucleophilic urea, resulting in high UOR performance. In practical utilization, NiCoMoCuOx Hy -driven UOR coupled cathodic hydrogen evolution reaction (HER) and carbon dioxide reduction reaction (CO2 RR), and harvested high value-added products of H2 and C2 H4 , respectively. This work clarifies a novel mechanism to improve electrocatalytic UOR performance through structure-induced interfacial microenvironment modulation.

Cobalt-Carbon nanotubes supported on V2O3 nanorods as sulfur hosts for High-performance Lithium-Sulfur batteries.

Exploring advanced sulfur cathode materials with high catalytic activity to accelerate the slow redox reactions of lithium polysulfides (LiPSs) is of great significance for lithium-sulfur batteries (LSBs). In this study, a coral-like hybrid composed of cobalt nanoparticle-embedded N-doped carbon nanotubes supported by Vanadium (III) oxide (V2O3) nanorods (Co-CNTs/C @V2O3) was designed as an efficient sulfur host using a simple annealing process. Characterization combined with electrochemical analysis confirmed that the V2O3 nanorods exhibited enhanced LiPSs adsorption capacity, and the in situ grown short-length Co-CNTs improved electron/mass transport and enhanced the catalytic activity for conversion to LiPSs. Owing to these merits, the S@Co-CNTs/C@V2O3 cathode exhibits effective capacity and cycle lifetime. Its initial capacity was 864 mAh g-1 at 1.0C and remained at 594 mAh g-1 after 800cycles with a decay rate of 0.039%. Furthermore, even at a high sulfur loading (4.5 mg cm-2), S@Co-CNTs/C@V2O3 also shows acceptable initial capacity of 880 mAh g-1 at 0.5C. This study provides new ideas for preparing long-cycle S-hosting cathodes for LSBs.

Solvent environment engineering to synthesize FeNC nanocubes with densely Fe-Nx sites as oxygen reduction catalysts for Zn-air battery.

Zeolitic imidazole framework (ZIF)-derived iron-nitrogen-carbon (FeNC) materials are expected to be high-efficiency catalysts for oxygen reduction reaction (ORR). However, increasing the density of active sites while avoiding metal accumulation still faces significant challenges. Herein, solvent environment engineering is used to synthesize the FeNC containing dense Fe-Nx moieties by adjusting the solvent during the ZIF precursor synthesis process. Compared with methanol and water/methanol, the aqueous media can provide a more moderate Fe content for the ZIF precursor, which facilitates the construction of high-density Fe-Nx sites and prevent the appearance of iron-based nanoparticles during pyrolysis. Therefore, the FeNC(C) nanocubes synthesized in an aqueous media have the highest single atom Fe loading (0.6 at%) among the prepared samples, which presents excellent oxygen reduction properties and durability under alkaline and acidic conditions. The advantage of FeNC(C) is proven in Zn-air batteries, with outstanding performance and long-term stability.

Bimetallic co-doping engineering over nickel-based oxy-hydroxide enables high-performance electrocatalytic oxygen evolution.

Enhancing the electrocatalytic oxygen evolution reaction (OER) performance is essential to realize practical energy-saving water electrolysis and CO2 electroreduction. Herein, we report a bimetallic co-doping engineering to design and fabricate nickel-cobalt-iron collaborative oxy-hydroxide on nickel foam that labeled as NiCoFeOxHy-NF. As expected, NiCoFeOxHy-NF exhibits an outstanding OER activity with current density of 10 mA cm-2 at 194 mV, Tafel slope of 53 mV dec-1, along with the robust long-term stability, which is significantly better than bimetallic NiCo and NiFe combinations. Comprehensive computational simulations and characterizations jointly unveil that the twisted ligand environment induced by heteroatoms ensures the balance strength between the metal-oxygen hybrid orbital states and the oxidized intermediates adsorption, thus lowering the oxygen cycling energy barriers for overcoming the sluggish OER kinetics. Moreover, a novel phase transition behavior is monitored by in-situ Raman spectra under OER operating conditions, which facilitates electron-mass transfer as well as boosts the exposure of activity sites. For practical applications, Ni2P-NF || NiCoFeOxHy-NF and Cu || NiCoFeOxHy-NF couples were constructed to realize high-efficiency water electrolysis and CO2 electrochemical reduction for the production of valuable H2 and C2H4, respectively. This work elucidates a novel mechanism by which bimetallic co-doping improves the electrocatalytic OER activity of nickel-based hydroxides.

Construction of Self-Supporting NiCoFe Nanotube Arrays Enabling High-Efficiency Alkaline Oxygen Evolution.

Enhancing the intrinsic activity and modulating the electrode-electrolyte interface microenvironment of nickel-based candidates are essential for breaking through the sluggish kinetics limitation of the oxygen evolution reaction (OER). Herein, a ternary nickel-cobalt-iron solid solution with delicate hollow nanoarrays architecture (labeled as NiCoFe-NTs) was designed and fabricated via a ZnO-templated electrodeposition strategy. Owing to the synergistic nanostructure and composition feature, NiCoFe-NT presents desirable alkaline OER performance, with a η10 and η500 of 187 and 310 mV, respectively, along with favorable long-term durability. In-depth analyses identify the heterogeneous nickel-based (oxy)hydroxide species derived from the oxidative reconstruction acting as an active contributor for oxygen evolution. Impressively, the regulatory mechanism of the catalytic performance by a rationally designed nanostructure was elucidated by compressive analyses; that is, the faster gas release processes induced by nanotube arrays can modulate the heterogeneous interface states during OER, which effectively facilitates the electrochemical charge-mass transfer to promote the reaction kinetics. To assess the practical feasibility, an alkaline water electrolyzer and a CO2 electrochemical reduction flow cell were constructed by coupling the anodic NiCoFe-NTs and cathodic nickel phosphides (Ni2P-NF) and metallic Cu electrocatalysts, respectively, both of which achieved high-efficiency operation.

Synergistic doping and structural engineering over dendritic NiMoCu electrocatalyst enabling highly efficient hydrogen production.

The development of non-precious metal electrocatalysts with remarkable activity is a major objective for achieving high-efficiency hydrogen generation. Here, a trimetallic electrocatalyst with a dendritic nanostructure, which is denoted as NiMoCu-NF, was fabricated on nickel foam via a gas-template electrodeposition strategy. By virtue of the metallic doping and structural optimization, NiMoCu-NF exhibits superior HER electrocatalytic activity with an overpotential of 52 mV at 10 mA cm-2. Additionally, the NiMoCu-NF-derived nickel-based (oxy)hydroxide species in the oxidation operating state deliver considerable electrocatalytic urea oxidation reaction (UOR) performance to match the efficient H2 generation, with a low voltage of 1.54 V to realize overall electrolysis at 50 mA cm-2. Impressively, combined experimental and simulation analysis demonstrate that the NiMoCu-NF with a favorable 3D nanostructure feature effectively regulates the heterogeneous interface states, inducing a "Gas Microfluidic Pumping" (GMP) effect that improved electron-mass transfer properties to accelerate the electrocatalytic reaction kinetics of either the HER or UOR.

A Facile Microwave Hydrothermal Method for Fabricating SnO2@C/Graphene Composite With Enhanced Lithium Ion Storage Properties.

SnO2@C/graphene ternary composite material has been prepared via a double-layer modified strategy of carbon layer and graphene sheets. The size, dispersity, and coating layer of SnO2@C are uniform. The SnO2@C/graphene has a typical porous structure. The discharge and charge capacities of the initial cycle for SnO2@C/graphene are 2,210 mAh g-1 and 1,285 mAh g-1, respectively, at a current density of 1,000 mA g-1. The Coulombic efficiency is 58.60%. The reversible specific capacity of the SnO2@C/graphene anode is 955 mAh g-1 after 300 cycles. The average reversible specific capacity still maintains 572 mAh g-1 even at the high current density of 5 A g-1. In addition, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are performed to further investigate the prepared SnO2@C/graphene composite material by a microwave hydrothermal method. As a result, SnO2@C/graphene has demonstrated a better electrochemical performance.

Synergistic Interfacial and Doping Engineering of Heterostructured NiCo(OH)x-CoyW as an Efficient Alkaline Hydrogen Evolution Electrocatalyst.

To achieve high efficiency of water electrolysis to produce hydrogen (H2), developing non-noble metal-based catalysts with considerable performance have been considered as a crucial strategy, which is correlated with both the interphase properties and multi-metal synergistic effects. Herein, as a proof of concept, a delicate NiCo(OH)x-CoyW catalyst with a bush-like heterostructure was realized via gas-template-assisted electrodeposition, followed by an electrochemical etching-growth process, which ensured a high active area and fast gas release kinetics for a superior hydrogen evolution reaction, with an overpotential of 21 and 139 mV at 10 and 500 mA cm-2, respectively. Physical and electrochemical analyses demonstrated that the synergistic effect of the NiCo(OH)x/CoyW heterogeneous interface resulted in favorable electron redistribution and faster electron transfer efficiency. The amorphous NiCo(OH)x strengthened the water dissociation step, and metal phase of CoW provided sufficient sites for moderate H immediate adsorption/H2 desorption. In addition, NiCo(OH)x-CoyW exhibited desirable urea oxidation reaction activity for matching H2 generation with a low voltage of 1.51 V at 50 mA cm-2. More importantly, the synthesis and testing of the NiCo(OH)x-CoyW catalyst in this study were all solar-powered, suggesting a promising environmentally friendly process for practical applications.

Correction: Complexing agent study via computational chemistry for environmentally friendly silver electrodeposition and the application of a silver deposit.

[This corrects the article DOI: 10.1039/C4RA05869K.].

Transition Metal and Nitrogen Co-Doped Carbon-based Electrocatalysts for the Oxygen Reduction Reaction: From Active Site Insights to the Rational Design of Precursors and Structures.

Considering the urgent requirement for clean and sustainable energy, fuel cells and metal-air batteries have emerged as promising energy storage and conversion devices to alleviate the worldwide energy challenges. The key step in accelerating the sluggish oxygen reduction reaction (ORR) kinetics at the cathode is to develop cost-effective and high-efficiency non-precious metal catalysts, which can be used to replace expensive Pt-based catalysts. Recently, the transition metal and nitrogen co-doped carbon (M-Nx /C) materials with tailored morphology, tunable composition, and confined structure show great potential in both acidic and alkaline media. Herein, the mechanism of ORR is provided, followed by recent efforts to clarify the actual structures of active sites. Furthermore, the progress of optimizing the catalytic performance of M-Nx /C catalysts by modulating nitrogen-rich precursors and porous structure engineering is highlighted. The remaining challenges and development prospects of M-Nx /C catalysts are also outlined and evaluated.

A theoretical study of atomically dispersed MN4/C (M = Fe or Mn) as a high-activity catalyst for the oxygen reduction reaction.

Carbon-based, non-noble metal catalysts for the oxygen reduction reaction (ORR) are crucial for the large-scale application of metal-air batteries and fuel cells. Density functional theory calculations were performed to explore the potential of atomically dispersed MN4/C (M = Fe or Mn) as an ORR catalyst in an acidic electrolyte and the ORR mechanism on MN4/C was systematically studied. The results indicated MN4 as the active site of MN4/C and a four-electron OOH transformation pathway as the preferred ORR mechanism on the MN4/C surface. The Gibbs free energy diagram showed that the rate-determining step of the FeN4/C and MnN4/C catalysts is the formation of the second H2O molecule and OOH*, respectively. FeN4/C exhibited higher thermodynamic limiting potential (0.79 V) and, thus, higher ORR activity than MnN4/C (0.52 V) in an acidic environment; its excellent catalytic performance is due to the nice electron structure and adsorption properties of the FeN4 site. Therefore, this work demonstrates that atomically dispersed MN4/C is a promising catalyst for the ORR.

Graphite N-C-P dominated three-dimensional nitrogen and phosphorus co-doped holey graphene foams as high-efficiency electrocatalysts for Zn-air batteries.

The search for metal-free catalysts for oxygen reduction reactions (ORRs) in energy storage and conversion devices, such as fuel cells and metal-air batteries, is highly desirable but challenging. Here, we have designed and synthesized controllable 3D nitrogen and phosphorous co-doped holey graphene foams (N,P-HGFs) as a high-efficiency ORR catalyst through structural regulation and electronic engineering. The obtained catalyst shows a half-wave potential of 0.865 V in alkaline electrolytes. It is found that Zn-air batteries with the N,P-HGFs-1000 air electrode exhibit excellent discharge performance and durability. Our study suggests that the remarkable ORR performance of N,P co-doped graphene is mainly due to the graphite N-C-P structure, where an enhanced charge density and increased HOMO energy level are confirmed by both experimental results and theoretical density-functional theory calculations.

A Facile and Flexible Approach for Large-Scale Fabrication of ZnO Nanowire Film and Its Photocatalytic Applications.

A novel strategy for large-scale synthesis of ZnO nanowire film is reported, which inherits the advantages of the solution-phase method and seeded growth process, such as low-temperature, efficient, economical, facile and flexible. It is easy to implement on various metals through room-temperature electrodeposition, followed by hydrothermal treatment at 90 °C, and suitable for industrialized production. The ZnO nanowires with an average wire diameter about 40 nm are in situ grown from and on nanocrystalline zinc coating, which forms a strong metallurgical bonding with the substrates. The p-type ZnO nanowire film has a well-preferred orientation along the (100) direction and a wurtzite structure, thereby displaying an effective photocatalytic capability for carcinogenic Cr6+ ions and CO2 greenhouse gas reduction under visible light irradiation. In addition to these features, the ZnO nanowire film is easy to recycle and, therefore, it has broad application prospects in contaminant degradation and renewable energy.

Nucleation and growth mechanism of a nanosheet-structured NiCoSe2 layer prepared by electrodeposition.

Ni-Co-Se layers have attracted a great deal of attention in the field of solar cells, electrocatalyst water splitting and supercapacitors. Electrodeposition is a simple, convenient and low-cost way to obtain Ni-Co-Se layers. However, until now, the electrochemical kinetics of the Ni-Co-Se system, including its growth and nucleation mechanisms, are still unclear. In present work a NiCoSe2 layer with a nanosheet structure was electrodeposited in a chloride bath. The electrochemical mechanisms of the Ni-Co-Se system were also studied. It is noted that the electrochemical kinetics of Ni-Co-Se electrodeposition can be influenced by both temperature and electrode material; however, temperature does not change the progressive nucleation process and mixed controlled growth mechanism of Ni-Co-Se. The diffusion coefficient D and charge-transfer coefficient α of the Ni-Co-Se system were calculated. The values of D obtained by cyclic voltammogram and chromoamperometry are close to each other at both 20 and 50 °C, respectively, and increase with the increase of temperature. Moreover, the activation energy E a was also calculated. Specially, a uniform 3D network-structure NiCoSe2 layer was electrodeposited on ITO glass at -0.9 V and 40 âˆ¼ 60 °C. The increased overpotential during deposition makes the NiCoSe2 layer more easily gather together; however, there is no significant effect on the surface morphology of the NiCoSe2 layer when the temperature is between 40 and 60 °C.

Designing robust underwater superoleophobic microstructures on copper substrates.

Recently, surfaces with a robust underwater superoleophobicity have attracted much attention. Although it is recognized that stable microstructures are significant for such surfaces, a clear picture of how microstructural features such as morphology, size, etc. influence their own stability and related wettability is still missing. Herein, three low adhesive underwater superoleophobic copper surfaces with different microstructures (hemispheric, pinecone-like, and honeycomb) were first prepared, and then the stability of these microstructures was examined by a series of physical and chemical damage experiments (sand grain abrasion, corrosion in acid/base solutions, etc.). The results indicate that the hemispheric microstructure is more stable than the other two microstructures and the corresponding surface has a robust underwater superoleophobicity. Theoretical simulation analysis further confirms the experimental results and reveals that different stabilities are ascribed to different stress distributions on these microstructures under an external force due to distinct microstructure shapes. Furthermore, based on the same design strategy, a robust underwater superoleophobic oil/water separation copper mesh film was also prepared. This work provides an insight into the effect of microstructural features on the stability and related underwater oil-repellent properties of superoleophobic copper surfaces, and could provide us with some fresh design ideas for robust superwetting surfaces.

Theoretical and experimental studies of the influence of gold ions and DMH on cyanide-free gold electrodeposition.

Quantum chemical calculations based on density functional theory (DFT) were employed to determine an appropriate gold source for gold electroplating and to ascertain the stable structures of gold-complexes in cyanide-free electrolyte. Based on the charge distribution of 5,5-dimethylhydantoin (DMH) and the bonding energy of gold complexes, Au3+ is the appropriate gold source for DMH-based gold electroplating electrolyte to get greater cathodic polarization and [Au(DMH)4]- with 2N(4)-Au coordination structure is the most stable form of gold ion in the electrolyte. The influence of DMH, used as the complexing agent, on electrochemical behaviors was investigated using cathodic polarization, cyclic voltammetry, and chronoamperometry measurements. With DMH as the complexing agent, the cathodic polarization of gold electrodeposition was significantly enhanced. DMH concentration was determined as 0.30 mol L-1 based on the investigation of the influence of the DMH concentration on cathodic polarization and gold electrodeposit micromorphology. The kinetic features based on cyclic voltammogram measurements revealed that the electrodeposition was an irreversible process under diffusion control with 0.30 mol L-1 DMH as the complexing agent. The ion and electron transfers were obviously inhibited by DMH. The gold electrodeposition process displayed progressive nucleation according to the Scharifker and Hills nucleation model with various applied potentials. The growth rate of the crystal nucleus was reduced by DMH and promoted by a negative shift of E ap.

Superior cycle performance and high reversible capacity of SnO2/graphene composite as an anode material for lithium-ion batteries.

SnO2/graphene composite with superior cycle performance and high reversible capacity was prepared by a one-step microwave-hydrothermal method using a microwave reaction system. The SnO2/graphene composite was characterized by X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, X-ray photoelectron spectroscopy, transmission electron microscopy and high resolution transmission electron microscopy. The size of SnO2 grains deposited on graphene sheets is less than 3.5 nm. The SnO2/graphene composite exhibits high capacity and excellent electrochemical performance in lithium-ion batteries. The first discharge and charge capacities at a current density of 100 mA g(-1) are 2213 and 1402 mA h g(-1) with coulomb efficiencies of 63.35%. The discharge specific capacities remains 1359, 1228, 1090 and 1005 mA h g(-1) after 100 cycles at current densities of 100, 300, 500 and 700 mA g(-1), respectively. Even at a high current density of 1000 mA g(-1), the first discharge and charge capacities are 1502 and 876 mA h g(-1), and the discharge specific capacities remains 1057 and 677 mA h g(-1) after 420 and 1000 cycles, respectively. The SnO2/graphene composite demonstrates a stable cycle performance and high reversible capacity for lithium storage.