Structure and Wettability Engineering of Polycrystalline Diamond Films Treated by Thermally Oxidation,Second Growth and Surface Termination

High-quality polycrystalline diamond films with dominated(100)-oriented grains are realized by combining the thermally oxidation and the homogeneous second growth processes.Moreover,we investigate the wettability property of the polycrystalline diamonds in various stages.Different surface structures(with various grain sizes,voids,and orientations,etc.)and terminations(hydrogen or oxygen)have significant effects on the wettability of polycrystalline diamond films.The wettability is further closely related to the polarity of solutions.By measuring the contact angle and calculating the dispersion and polarity components,we estimate the surface energy of polycrystalline diamond films,and explore the factors affecting the surface energy.The modulations in growth quality and wettability property of polycrystalline diamond films provide valuable data for development of diamond-based multiple devices in practical applications.

Pressure-Induced Structural Transitions of the Zinc Sulfide Nano-particles with Different Sizes

ZnS nano-particles with average sizes of 10 nm and 5 nm were fabricated by sol-gel method, and their pressure-induced phase transformations were in-situ examined in a diamond anvil cell by energy dispersive X-ray diffraction （EDXD） from ambient pressure to 35.0 GPa. From the obtained interplanar spacing data,the volume compression ratios were derived at different pressures, and then the bulk modulus and its pressure derivative were obtained by fitting to the Murnaghan equation. It is found that both ZnS nano-particles initially in the zinc-blende phase transformed to cubic NaCl structure in the presence of pressure and the transition was reversible when the pressure was released. Moreover, it is suggested that a smaller particle size will induce a larger transition pressure.

Structural model of substitutional sulfur in diamond

Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literature.The energy difference of C2vand C3vstructures is qualitatively affected by the supercell size,and the 216-atom supercell could be proposed as the minimum to obtain stable configuration of substitutional S in diamond.Using supercells of up to 512 atoms,the donor level of substitutional S with C2vsymmetry is deep.

Coordination engineering of cobalt phthalocyanine by functionalized carbon nanotube for efficient and highly stable carbon dioxide reduction at high current density

Coordination engineering can enhance the activity and stability of the catalyst in heterogeneous catalysis.However,the axial coordination engineering between different groups on the carbon carrier and molecular catalysts in the electrocatalytic carbon dioxide reduction reaction(CO_(2)RR)has been studied rarely.Through coordination engineering strategy,a series of amino(NH_(2)),hydroxyl(OH),and carboxyl(COOH)groups functionalized carbon nanotubes(CNT)immobilized cobalt phthalocyanine(CoPc)catalysts are designed.Compared with no groups,OH groups and COOH groups,NH_(2)groups can effectively change the coordination environment of the central metal Co,thereby significantly increasing the turnover frequency(TOF)(31.4 s^(-1)at-0.6 V vs.RHE,CoPc/NH_(2)-CNT>CoPc/OH-CNT>CoPc/COOH-CN>CoPc/CNT).In the flow cell,the CoPc/NH_(2)-CNT catalyst has high carbon monoxide(CO)selectivity at high current density(~100%at-225 mA·cm^(-2),~96%at-351 mA·cm^(-2)).Importantly,the CoPc/NH_(2)-CNT catalyst can operate stably for 100 h at 225 mA·cm^(-2).Theoretical calculations reveal that CoPc/NH_(2)-CNT catalyst is beneficial to the formation of^(*)COOH and desorption of^(*)CO,thus promoting CO_(2)RR.This work provides an excellent platform for understanding the effect of coordination engineering on electrocatalytic performance and promotes a way to explore efficient and stable catalysts in other applications.

Hot electron assisted photoelectrochemical water splitting from Audecorated ZnO@TiO_(2) nanorods array

Engineering of semiconductor nanomaterials is critical to enhance the photoelectrochemical(PEC)performance for water splitting.However,semiconductors often show the low light absorption,slow charge transfer,and easy recombination of carriers,thus leading to the low catalytic efficiency.In this work,we show facile synthesis of ZnO@TiO_(2) core–shell nanorods(NRs)arrays modified with Au nanoparticles(NPs)as the photoelectrode for PEC water splitting.Impressively,the obtained ZnO@TiO_(2)(15 nm)/Au(8 nm)array shows the maximum photocurrent density of 3.14 mA/cm^(2) at 1.2 V vs.reversible hydrogen electrode(RHE),2.6 times and 1.7 times higher than those obtained from ZnO NRs and ZnO@TiO_(2)(15 nm)arrays.The electric-field simulation and transient absorption spectroscopy show that the Au-decorated core–shell nanostructures have an enhanced hot electron generation and prolonged decay time,indicating effective charge transfer and recombination inhibition of carriers.This work provides an efficient preparation strategy for photoelectrodes as well as great potential for the large-scale development of this technology.

Strong High Entropy Alloy-Support Interaction Enables Efficient Electrocatalytic Water Splitting at High Current Density

In electrocatalysis, the stability issue between catalyst and support still needs great attention. Here, a series of highentropy alloy nanoparticles(HEA-NPs) embedded in carbon cloth(CC) were synthesized by using the scalable strategy-microwave heating. Among them, PtRhCoNiCu/CC exhibits outstanding hydrogen evolution reaction(HER) activity(19 and 170 mV overpotential at 10 and 1000 mA cm^(-2)) and stability(150 h), outperforming other recently reported HEAs catalysts. IrRuCoNiCu/CC displays superior oxygen evolution reaction(OER) activity(166 and 354 mV overpotential at 10 and 1000 m A cm^(-2)) and stability(150 h), and shows a lower overpotential than recently reported HEA catalysts. In water splitting, IrRuCoNiCu/CC(+)//Pt Rh Co Ni Cu/CC(-) electrolyzer achieves 500 m A cm^(-2)(1000 m A cm^(-2)) high current density at 1.76 V(1.88 V) and exhibits excellent stability, which is one of the best catalysts currently. Therefore, the novel supported HEA catalyst with high stability is expected to be a promising candidate material for industrialized water splitting.

Dual-functional conductive nanofilm absorber

Converting solar energy by to other forms of energy has attracted a lot of interest from academy to industry.However,the overall utilization efficiency of solar energy is inferior due to the limited effective solar spectrum range.Here,in order to utilize the broadband solar spectrum more efficiently,a novel hybrid absorber structure was proposed,which consists of a four-layer planar nanofilm with dual functions of heat absorption and photocatalysis.The average absorption in the visible range is larger than 0.95,and in the near-infrared spectral region,the average absorption is still larger than 0.85.The overall absorption of the absorber is over 0.86,while the thermal emittance is lower than 0.04,which can lead to remarkable thermal utilization efficiency.Moreover,the full range of the solar irradiance can be utilized by incorporating the photocatalytic TiO_(2) layer into the absorber,which is active in the ultraviolet spectral range.In addition to the broadband spectral usage,the virtues of inexpensiveness and environmental friendliness make it a facile alternative to be applied in solar energy transformation.

Noble metal aerogels rapidly synthesized by ultrasound for electrocatalytic reaction

Noble metal aerogels(NMAs), belonging to the porous material, have exhibited excellent catalytic performance. Although the synthesis method continues to improve, it still exists some problems which hindered the experimental process, such as high concentration of noble metal precursors, long synthesis cycle, expensive production cost, and uncontrollable ligament length. In this work, ultrasonic wave and reducing agent Na BH;were simultaneously applied to gelation process. With the cavitation of ultrasound,it can generate huge energy with heating and stirring, thus gelation reaction proceeded quickly, and even completed the process in only a few seconds, that is much faster than the recorded. A wide concentration range was successfully expanded from 0.02 mmol/L to 62.5 mmol/L. Further, we extended this method to a variety of noble metal elements(Au, Ru, Rh, Ag, Pt, Pd), and this method is adaptive for the synthesis of single metal aerogels(Au, Ag, Ru, Rh, Pd), bimetal and trimetal aerogels(Au-Ag, Au-Rh, Au-Ru, Au-Pt,Au-Pd, Au-Pt-Pd). In addition, the ligament size of alloy aerogels are 10 nm or less. Moreover, their brilliant properties were demonstrated in hydrogen evolution reaction(HER) and ethanol oxidation reaction(EOR).

Acidic electroreduction CO_(2)to formic acid via interfacial modification of Bi nanoparticles at industrial-level current

Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)in acidic media is a promising approach to overcome the unavoidable formation of carbonates in alkaline or neutral electrolytes.However,the proton-rich environment near the catalyst surface favors hydrogen evolution reactions(HER),leading to lower energy efficiency of the desired products,especially in industrial-level current densities.Here,quaternary ammonium cationic surfactant(cetyltrimethylammonium bromide(CTAB))was introduced into acidic electrolyte to modulate the interfacial microenvironment,which greatly enhanced CO_(2)electroreduction to formic acid(HCOOH)at the Bi/C nanoparticles electrode.Using a Bi/C nanoparticles electrode with CTAB added,constant production of formic acid was enabled with a cathodic energy efficiency of>40%and maximum FE_(HCOOH)(FE=Faradaic efficiency)of 86.2%at−400 mA·cm^(−2)over 24 h.Combined with in-situ attenuated total reflection Fourier transform infrared spectroscopy,the concentration of*OCHO intermediates significantly increased after CTAB modification,confirming that the hydrophobic interface microenvironment formed by dynamic adsorption of positively charged long alkyl chains on Bi/C nanoparticle electrodes inhibited HER and improved the selectivity of CO_(2)RR to HCOOH.