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Carbon neutral becomes one of the most important environmental goals due to the excessive emission of CO2. The reduction of CO2 into valuable chemicals or fuels is one of the important strategies to solve the carbon cycle and achieve carbon neutral. Atomic site catalysts show high activity and selectivity in CO2 reduction reactions. However, due to the complexity of the multistep CO2 reduction reaction, it is difficult for an isolated atomic site to achieve multi-functional requirements. Bimetallic atomic site catalysts can take advantage of the high activity and selectivity of atomic sites, and the synergies between bimetallic atomic sites can fully optimize the CO2 reduction reactions. In this review, firstly, we summarize the design considerations of catalysts for CO2 reduction reactions. Secondly, the preparation and characterization of bimetallic atomic site catalysts are reviewed. Thirdly, the role of bimetallic atomic sites in CO2 reduction reactions was analyzed in detail.

Atomically dispersed transition metals on carbon-based aromatic substrates are an emerging class of electrocatalysts for the electroreduction of CO2. However, electron delocalization of the metal site with the carbon support via d-π conjugation strongly hinders CO2 activation at the active metal centers. Herein, we introduce a strategy to attenuate the d-π conjugation at single Ni atomic sites by functionalizing the support with cyano moieties. In situ attenuated total reflection infrared spectroscopy and theoretical calculations demonstrate that this strategy increases the electron density around the metal centers and facilitates CO2 activation. As a result, for the electroreduction of CO2 to CO in aqueous KHCO3 electrolyte, the cyano-modified catalyst exhibits a turnover frequency of ~22,000 per hour at −1.178 V versus the reversible hydrogen electrode (RHE) and maintains a Faradaic efficiency (FE) above 90% even with a CO2 concentration of only 30% in an H-type cell. In a flow cell under pure CO2 at −0.93 V versus RHE the cyano-modified catalyst enables a current density of −300 mA/cm2 with a FE above 90%.

In this work, effect of Mo content on the microstructure, thermal conductivity, and corrosion resistance of the die steels was investigated by optical microscopy, scanning electron microscopy, x-ray diffraction, laser thermal conductivity meter, electrochemical experiments, and pitting tests. The microstructure of the die steels is mainly composed of lath-shaped tempered martensite. At all the tested temperatures, the thermal conductivity of the die steels is decreased with the increase in Mo content from 1.2 to 5.0 wt.%. However, electrochemical experiments indicate that increase in Mo content in the die steels can reduce the corrosion current density and increase the charge transfer resistance in 0.5 mol·L−1 HCl solution. Furthermore, it was found that Mo in the die steels is beneficial to decrease weight loss and pitting corrosion rate, which improves the pitting corrosion resistance of the die steels.

Electrocatalytic CO2 reduction reaction (CO2RR) to obtain C2 products has drawn widespread attentions. Copper-based materials are the most reported catalysts for CO2 reduction to C2 products. Design of high-efficiency pseudo-copper catalysts according to the key characteristics of copper (Cu) is an important strategy to understand the reaction mechanism of C2 products. In this work, density function theory (DFT) calculations are used to predict nickel-zinc (NiZn) alloy catalysts with the criteria similar structure and intermediate adsorption property to Cu catalyst. The calculated tops of 3d states of NiZn3(001) catalysts are the same as Cu(100), which is the key parameter affecting the adsorption of intermediate products. As a result, NiZn3(001) exhibits similar adsorption properties with Cu(100) on the crucial intermediates *CO2, *CO and *H. Moreover, we further studied CO formation, CO hydrogenation and C-C coupling process on Ni-Zn alloys. The free energy profile of C2 products formation shows that the energy barrier of C2 products formation on NiZn3(001) is even lower than Cu(100). These results indicate that NiZn3 alloy as pseudo-copper catalyst can exhibit a higher catalytic activity and selectivity of C2 products during CO2RR. This work proposes a feasible pseudo-copper catalyst and provides guidance to design high-efficiency catalysts for CO2RR to C2 or multi-carbon products.

Iron phthalocyanine (FePc) is a promising non-precious catalyst for the oxygen reduction reaction (ORR). Unfortunately, FePc with plane-symmetric FeN4 site usually exhibits an unsatisfactory ORR activity due to its poor O2 adsorption and activation. Here, we report an axial Fe–O coordination induced electronic localization strategy to improve its O2 adsorption, activation and thus the ORR performance. Theoretical calculations indicate that the Fe–O coordination evokes the electronic localization among the axial direction of O–FeN4 sites to enhance O2 adsorption and activation. To realize this speculation, FePc is coordinated with an oxidized carbon. Synchrotron X-ray absorption and Mössbauer spectra validate Fe–O coordination between FePc and carbon. The obtained catalyst exhibits fast kinetics for O2 adsorption and activation with an ultralow Tafel slope of 27.5 mV dec−1 and a remarkable half-wave potential of 0.90 V. This work offers a new strategy to regulate catalytic sites for better performance., Iron phthalocyanine with a 2D structure and symmetric electron distribution around Fe-N4 active sites is not optimal for O2 adsorption and activation. Here, the authors report an axial Fe–O coordination induced electronic localization strategy to enhance oxygen reduction reaction performance.

The effects of Nb addition on the microstructure and corrosion resistance of the as-rolled Ti-stabilized Fe-17Cr ferritic stainless steels were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction, pitting tests, and electrochemical measurements. TiN precipitate tends to form in the microstructure of Ti-stabilized Fe-17Cr ferritic stainless steel. After 0.1 wt. % Nb addition, (Ti, Nb) (C, N) composite precipitates with MgO and Al2O3 core form in the microstructure. After adding 0.1 wt. % Nb, the corrosion rate of the Ti-stabilized Fe-17Cr ferritic stainless steel in FeCl3 solution is decreased significantly. The corrosion current densities decrease in HNO3, NaOH, and NaCl solutions, and the pitting corrosion potentials can be improved in NaCl solution for the Fe-17Cr ferritic stainless steel with 0.1 wt. % Nb addition.

The chirp managed laser (CML) mainly includes a directly modulated laser followed by an optical spectrum reshaper (OSR) filter. In this paper, an integral layer-peeling method has been applied to synthesize the OSR filter with the desired reflection spectrum, which breaks the trade-off between the filter bandwidth and the filter slope steepness inherently existing in the FP etalon based filter, and hence greatly facilitates the optimization design of the OSR for a better transmission performance of a CML. Using this approach, we have, respectively, investigated the optimization design of the OSR filter in terms of the edge slope and the 3 dB bandwidth in the CML modulated at 10 and 25 Gb/s, through studying their transmission performances over the standard single-mode fiber. With the optimum design of OSR, the longest transmission distances at which the power penalty is 1 dB at a bit error rate of 10−12 are 135 and 18 km for the 10 and 25 Gb/s CML, respectively.

In this paper, a 1310 nm InAlGaAs/InP multiple quantum well ridge waveguide FP laser with a built-in wavelength detuned band-pass filter has been fabricated and investigated in experiments. When compared to the reference FP laser fabricated in the same wafer, it is observed that the root-mean-square spectral width can be approximately reduced to half; and moreover, significant improvements on the transmission performances in terms of the power penalty at given transmission distance and the longest transmission distance at given bit error rate, have been achieved for the proposed laser at the same fabrication cost.

In this paper, we propose a DFB laser with a horn ridge waveguide (HRW) to suppress the longitudinal spatial hole burning (LSHB) effect in the lasers cavity, thus to reduce the rolloff at low frequency. The simulation result shows that HRW DFB lasers could significantly suppress the LSHB effect and its modulation bandwidth is increased by 14% comparing with the conventional straight ridge waveguide (RW) DFB lasers when the normalized coupling coefficient (κL) is 3.0. The calculated eye diagrams of HRW DFB lasers under direct 25 Gbps modulation have clearer opening than that of the conventional RW DFB lasers. These superior properties are due to the suppression of the LSHB effect by the HRW structure.

In the present study, the effects of Mg, Cu, Sc and Zr combined additions on the microstructure and mechanical properties of hypoeutectic Al–Si cast alloy were systematically investigated. Characterization techniques such as optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron back-scatter diffraction (EBSD), atomic force microscopy (AFM), transmission electron microscope (TEM), Brinell hardness tester and universal testing machine were employed to analyze the microstructure and mechanical properties. The results showed that Sc served as modifier on the microstructure of Al–3Si–0.45Mg–0.45Cu–0.2Zr alloys, including modification of eutectic Si and grains. Extraordinarily, grain refinement was found to be related to the primary particles, which exhibited a close orientation to matrix. After T6 heat treatment, the grain structures were composed of nano-scaled secondary Al3(Sc, Zr) precipitates and spherical eutectic Si. Combined with T6 heat treatment, the highest hardness, yield strength, ultimate tensile strength and elongation were achieved in 0.56 wt.% Sc-modified alloy. Interestingly, the strength and ductility had a similar tendency. This paper demonstrated that combined additions of Mg, Cu, Sc and Zr could significantly improve the microstructure and performance of the hypoeutectic Al–Si cast alloy.

The relationship between morphology and crystallography of an entangled lathy ferrite during directional solidification in Fe–Cr–Ni alloy has been investigated. During solidification, morphology of the lathy ferrite depends on the orientation relationship between the lathy ferrite and austenite. When the plane in the austenite substrate is (111)γ, “Y-shaped” lathy ferrite grows in an entangled cluster and the orientation relationship between the lathy ferrite and austenite is the Nishiyama–Wassermann relationship. Lathy ferrite is preferentially elongated along γ and γ directions on (111)γ plane due to lower misfit. The included angle among the “Y-shaped” lathy ferrite is about 120° because the angle between each pair of [211]γ, [112]γ, and [121]γ crystal directions is equal to 120°. Formation mechanism of the perpendicular lathy ferrite has also been analyzed according to the relationship between γ and γ and γ and γ on (111)γ and γ plane. This indicates that required crystal morphology of the lathy ferrite in the solidified microstructure can be obtained by controlling the crystal plane of austenite.

Microstructure, corrosion behavior and evolution of hot-rolled high-carbon–chromium bearing steel were investigated using scanning electron microscopy and energy dispersive spectrometer (EDS). The results show that corrosion initiates adjacent to the network carbide, which is the initial austenite grain boundary. With the further increase in corrosion time, corrosion fraction is increased and extended into the grains. Finally, the whole grain near the network carbide is etched off and the grain boundary is detached from the sample, which forms the corroded holes. Based on the EDS analyses, it is confirmed that this corrosion behavior is resulted from the depletion of Cr as solid solute at the grain boundary. The depletion of Cr is the result of the formation of Cr carbide near the grain boundary.

Hydrogen bonding configurations and hydrogen content in hydrogenated amorphous silicon (a-Si:H) thin films prepared at different precursor gas temperatures with undiluted silane have been investigated by means of Fourier transform infrared (FTIR) spectroscopy. The results show that the gas temperature before precursor gases entering the glow-discharge zone remarkably influences the hydrogen bonding configurations and the hydrogen content in a-Si:H thin films. The hydrogen content decreases from 18% down to 11% when increasing the gas temperature from room temperature (RT) to 433 K. Meanwhile, the clustered hydrogen at the physical film surface or at the internal surfaces of the microvoids decreases, indicating that a-Si:H thin films are densified at higher precursor gas temperatures. For a-Si:H thin films deposited at gas temperature of 433 K, the isolated silicon-hydrogen bonding configuration is predominant in the testing films.

A novel reversible addition-fragmentation chain transfer (RAFT) reagent bearing triphenylamine (TPA) group, 4-diphenylamino-dithiobenzoic acid benzyl ester (DDABE), was designed and synthesized. It was used in the RAFT polymerizations of styrene (St) and methyl acrylate (MA) to prepare end-functionalized polymers. The results of the polymerization showed that the RAFT polymerizations could be well controlled using DDABE as the RAFT agent. Number-average molecular weight (Mn,GPC) increased linearly with monomer conversion, and molecular weight distributions were relatively narrow (PDI< 1.50). The results of chain-extension reaction, 1H NMR spectra and UV/Vis spectra confirmed that most of the polymers chains were end-capped by the functional triphenylamine (TPA) groups. The effect of feed molar ratios of St/DDABE/AIBN on polymerization was investigated.