Single-phase bimetal sulfide or metal sulfide heterojunction:Which one is better for reversible oxygen electrocatalyst?

Bimetallic sulfides,integrating the merits of individual components,are ideal structures for efficient electrocatalysis.However,for bimetallic sulfides including metal sulfide heterojunctions(MSH)and singlephase bimetallic sulfides(SBS),it is still unclear about which one has better catalytic activity toward reversible oxygen catalysis and its difference on catalytic mechanism.In this work,we demonstrate a bimetallic sulfide electrocatalyst that could transform from metal sulfide heterojunction(CoS/FeS)to single-phase bimetallic sulfide(CoFeS_(2))through a facile temperature control strategy.The single-phase bimetallic sulfide(CoFeS_(2))affords high intrinsic activity,fast reaction kinetics and superior durability toward oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Density functional theory(DFT)simulations reveal that the(CoFeS_(2))has homogeneous electron distribution of the CoFeS_(2)structure,improves the central energy level of d band,and optimizes the O*and OOH*intermediate and efficiently reduces the energy barrier of the reaction rate-determining step(RDS).The assembled rechargeable zincair battery is more stable than the Pt/C and IrO_(2) assemblies due to the excellent electrocatalytic activity and stability of CoFeS_(2)/NC,suggesting that it has potential for use in practical applications.

Development and validation of depletion code system IMPC Burnup for ADS

Depletion calculation is important for studying the transmutation efficiency of minor actinides and longlife fission products in accelerator-driven subcritical reactor system(ADS). Herein the Python language is used to develop a burnup code system called IMPC-Burnup by coupling FLUKA, OpenMC, and ORIGEN2. The program is preliminarily verified by OECD-NEA pin cell and IAEAADS benchmarking by comparison with experimental values and calculated results from other studies. Moreover,the physics design scheme of the CIADS subcritical core is utilized to test the feasibility of IMPC-Burnup program in the burnup calculation of ADS system. Reference results are given by the COUPLE3.0 program. The results of IMPC-Burnup show good agreement with those of COUPLE3.0. In addition, since the upper limit of the neutron transport energy for OpenMC is 20 MeV, neutrons with energies greater than 20 MeV in the CIADS subcritical core cannot be transported; thus, an equivalent flux method has been proposed to consider neutrons above 20 MeV in the OpenMC transport calculation. The results are compared to those that do not include neutrons greater than 20 MeV. The conclusion is that the accuracy of the actinide nuclide mass in the burnup calculation is improved when the equivalent flux method is used. Therefore, the IMPC-Burnup code is suitable for burnup analysis of the ADS system.

Hierarchically Structured Three-Dimensional Carbon-Based Integrated Electrodes with Enhanced Pseudocapacitance and Deformability

Compressible supercapacitors play an increasingly significant role in flexible sensors and wearable electronic devices.However,the integration of mechanical compressibility and excellent electrochemical performance into a single device remains a challenge.Herein,we demonstrate a compressible and high-performance supercapacitor based on an N-doped carbon foam elastomer with hierarchical carbon nanotubes.Hierarchically structured Fe3C@N-doped carbon nanotubes/N-doped carbon foam and Ni@N-doped carbon nanotubes/N-doped carbon foam have been synthesized via a simple and universal self-catalytic strategy.The hierarchical structural features of self-catalytic N-doped carbon nanotubes serve as a cushion when the composite is subjected to an external force,exhibiting excellent mechanical properties with a maximum compressive strain of 80%and fatigue resistance of 1000 cycles.Moreover,the different electroactive potentials of the transition-metal species in the composites provide the assembly with a maximum operating voltage of 1.4 V,which shows a maximum energy density of∼10.74 Wh kg^(−1)(0.084 mWh cm^(−3))at the power density of∼179.2 W kg^(−1)(1.4 mWh cm^(−3)),and retains 88.4%of the original capacitance after 20,000 charge–discharge cycles,even at a strain of 80%.This work paves the way for controllable fabrication of compressible electrodes and supercapacitors.

S, N co-doped carbon nanotube-encapsulated core-shelled CoS2@Co nanoparticles： efficient and stable bifunctional catalysts for overall water splitting

Hydrogen, serving as a clean, sustainable energy source, may be mainly produced from electrolysis water.Herein, we report cobalt disulphide encapsulated in self-catalyzed carbon nanotubes(S,N-CNTs/CoS_2@Co) serving as a bifunctional catalyst, which exhibits excellent hydrogen evolution reaction performance(10.0 mA cm^(-2) at 0.112 V, and low Tafel slope for 104.9 mV dec^(-1)) and oxygen evolution reaction performance(10.0 mA cm^(-2) at 1.57 V, and low Tafel slope for 76.1 mV dec^(-1)), meanwhile with a strong stability at various current densities. In-depth study reveals that the excellent catalytic properties can be mainly attributed to the increased catalytic sites induced by S, N co-doping, the improved electronic conductivity derived from the carbon nanotubes, and Mott-Schottky effect between the metal cobalt and semiconductive cobalt disulfide. Notably, when the bifunctional catalysts are applied to overall water splitting, a low potential of 1.633 V at the current density of 10.0 mA cm^(-2) is achieved, which can compete with the precious metal catalyst benchmarks in alkaline media, demonstrating its promising practicability in the realistic water splitting application. This work elucidates a practicable way to the design of transition metal and nano-carbon composite catalysts for a broad application in the fields of energy chemistry.

Cascaded electron transition in CuWO4/CdS/CDs heterostructure accelerating charge separation towards enhanced photocatalytic activity

CuWO4,as an n-type oxide semiconductor with a bandgap of 2.2 eV,has stimulated enormous interest as a potential broad-spectrum-active photocatalyst for environmental pollution remediations.However,rapid charge recombination greatly hinders its practical applications.Herein,we present a cascaded electron transition pathway in a ternary heterostructure consisting of CdS quantum dots,carbon dots(CDs)and CuWO4 hollow spheres,which proves to greatly facilitate the photogenerated electron-hole separation,and eventually boosts the degradation efficiency of phenol and congo red by 100%and 46%compared to bare CuWO4.The enhanced performance of the CuWO4/CdS/CDs heterostructure mainly originates from the unidirectional electron migration from CdS to CuWO4 and then to the organics through CDs.This work elucidates the electron transfer kinetics in multi-phase system and provides a new design paradigm for optimizing the properties of CuWO4 based photocatalysts.

Electrochemical disproportionation strategy to in-situ fill cation vacancies with Ru single atoms

Supported single-atom catalysts(SACs)possess high catalytic activity,selectivity,and atom utilizations.However,the atom coordination environments of SACs are difficult to accurately regulate due to the high complexity of coordination site and local environment of support.Herein,we develop an in-situ electrochemical cation-exchange method to fill the cation vacancies in MnO_(2)with Ru single atoms(SAs).This obtained catalyst exhibits high mass activity,which is~44 times higher than commercial RuO2 catalyst and excellent stability,superior to the most state-of-the-art oxygen evolution reaction(OER)catalysts.The experimental and theoretical results confirm that the doped Ru can induce charge density redistribution,resulting in the optimized binding of oxygen species,and the strong covalent interaction between Ru and MnO2 for resisting oxidation and corrosion.This work will provide a new concept in the synthesis of well-defined local environments of supported SAs.

Constructing Z-schemeβ-Bi_(2)O_(3)/ZrO_(2)heterojunctions with 3D mesoporous SiO_(2)nanospheres for efficient antibiotic remediation via synergistic adsorption and photocatalysis

A series of Z-schemeβ-Bi_(2)O_(3)/ZrO_(2)hetero-junction composites containing three-dimensional(3D)mesoporous silica nanospheres(MSNs)were synthesized as efficient catalysts for antibiotic remediation.The obtained MSN/β-Bi_(2)O_(3)/ZrO_(2)ternary composites possess novel lamellar cross structure,which is well constructed byβ-Bi_(2)O_(3)nanosheets,3D MSNs,and ZrO_(2)nanoparticles.The optimal sample BZS-2(Bi∶Zr∶Si=1∶0.4∶0.33)shows an adsorptive-photocatalytic removal efficiency of 92.7%towards levofloxacin(LVF)and a total organic carbon(TOC)removal efficiency of 60.0%under simu-lated solar light irradiation for 100 min.BZS-2 can also remove 90.1%and 91.2%of tetracycline hydrochloride(TC)and oxytetracycline hydrochloride(OTC),respectively,and themaximum adsorptioncapacityof TCover BZS-2is almost 10 times that of-BiO.Theimprovement ofphotocatalytic activitycan bemainly attributed to the enhanced visible-light adsorption capacity and more efficientseparationof photogenerated electron-hole pairs.A possible Z-scheme photocatalytic mechanism of p BiO/ZrOheterojunctions based on valence band offset(AEvBo)andconduction band offset(EcBo)isproposed.This study provides an efficient way to construct novel mesoporous ternary photocatalyst with increased accessible surface area and active sites for treatment of antibiotics by synergistic adsorption and photocatalysis.

Transition metal-based electrocatalysts for overall water splitting

Electrochemical overall water splitting is attracting a broad focus as a promising strategy for converting the electrical output of renewable resources into chemical fuels,specifically oxygen and hydrogen.However,the urgent challenge in water electrolysis is to search for low-cost,high-efficiency catalysts based on earth-abundant elements as an alternative to the high-cost but effective noble metal-based catalysts.The transition metal-based catalysts are more appealing than the noble metal catalysts because of its low cost,high performance and long stability.Some recent advances for the development in overall water splitting are reviewed in terms of transition metal-based oxides,carbides,phosphides,sulfides,and hybrids of their mixtures as hybrid bifunctional electrocatalysts.Concentrating on different catalytic mechanisms,recent advances in their structural design,controllable synthesis,mechanistic insight,and performance-enhancing strategies are proposed.The challenges and prospects for the future development of transition metal-based bifunctional electrocatalysts are also addressed.©2021 Chinese Chemical Society and Institute of Materia Medica,Chinese Academy of Medical Sciences.

Visible light-assisted peroxydisulfate activation via hollow copper tungstate spheres for removal of antibiotic sulfamethoxazole

The contamination of antibiotics in aqueous environment causes increasing concerns recently.Lightassisted activation of peroxydisulfate(PDS)has been demonstrated as an efficient technology for re moval of contamination in water.Herein,a hollow sphere of CuWO_(4)(h-CuWO_(4))was employed as a visible lightactivated photocatalyst for the activation of PDS,and following with high removal efficiency(98%)of antibiotic sulfamethoxazole(SMX).Under visible light irradiation,the degradation rate on hollow structures system is nearly 2 times higher than the traditional solid CuWO_(4) spheres.Furthermore,the underlying mechanism and detailed pathway of SMX degradation were proposed based on density functional theory(DFT)calculations and liquid chromatography-mass spectrometry(LC-MS).This work provides a new feasible way for advanced oxidation processes to remove antibiotics SMX in heterogeneous system,and open up new application possibilities of CuWO_(4)-based materials.

Enhanced electron transport through two-dimensional Ti_(3)C_(2) in dye-sensitized solar cells

Two-dimensional(2D)Ti_(3)C_(2) material has a wide range of photovoltaic applications due to its unique electronic,optical,and plasmonic properties.Herein,we present a series of Ti_(3)C_(2)(0,0.6,0.8;wt%)nanosheets-modified P25 nanoparticles as photoanode films for dye-sensitized solar cells(DSSCs).The DSSC based on P25 and 0.6 wt%Ti_(3)C_(2) photoanode achieves a fairly good efficiency(9.22%),which greatly exceeds the counterpart based on the pure P25(7.16%).Benefiting from high light scattering and metallic electrical conductivity of Ti_(3)C_(2) additive,the P25/Ti_(3)C_(2)-based DSSC exhibits a superior behavior of controlling photogenerated charge recombination compared with pure P25 one.

A topotactic tailored synthesis of waxberry-like mixed-phase TiO_(2) hollow spheres for dye-sensitized solar cells

The waxberry-like mixed-phase TiO_(2)hollow microstructures (WMTHMs) are controllably prepared via a topotactic synthetic method,involving the synthesis of monodispersed Ca TiO_(2)precursors by a solvothermal method and subsequently transforming them into TiO_(2)through a Na_(2)EDTA-assisted ion-exchange process.The ratio of anatase-rutile is adjustable,and the two phases are connected well with each other.WMTHMs are composed of radially aligned nanorods,speeding up the electron transport.The optimum WMTHMs sample shows a specific surface area of 68.05 m^(2)/g and exhibits an excellent light scattering capacity.The cell based on WMTHMs light scattering layer obtained an optimal efficiency of 9.12%.The improvement of cell efficiency is mainly attributed to the high specific surface area,the efficient light scattering,the appropriate ratio of anatase-rutile,the staggered bandgap structure,and the convenient one-dimensional electron transport channel.

Heterostructures of NiFe LDH hierarchically assembled on MoS_(2) nanosheets as high-efficiency electrocatalysts for overall water splitting

Typically,rational interfacial engineering can effectively modify the adsorption energy of active hydrogen molecules to improve water splitting efficiency.NiFe layered double hydroxide(NiFe LDH)composite,an efficient oxygen evolution reaction(OER)catalyst,suffers from slow hydrogen evolution reaction(HER)kinetics,restricting its application for overall water splitting.Herein,we construct the hierarchical MoS_(2)/NiFe LDH nanosheets with a heterogeneous interface used for HER and OER.Benefiting the hierarchical heterogeneous interface optimized hydrogen Gibbs free energy,tens of exposed active sites,rapid mass-and charge-transfer processes,the MoS_(2)/NiFe LDH displays a highly efficient synergistic electrocatalytic effect.The MoS_(2)/NiFe LDH electrode in 1 mol/L KOH exhibits excellent HER activity,only 98 mV overpotential at 10 mA/cm^(2).Significantly,when it assembled as anode and cathode for overall water splitting,only 1.61 V cell voltage was required to achieve 10 mA/cm^(2)with excellent durability(50 h).

Molybdenum phosphide(MoP) with dual active sites for the degradation of diclofenac in Fenton-like system

The leaching and non-recoverability of mental ions have always limited the practical application of Fenton-like processes. For the first time, we synthesized molybdenum phosphide (MoP) with dual active sites for the degradation of diclofenac (DCF) in the Fenton-like process. The DCF degradation rate constant (k) of MoP + H_(2)O_(2) process was calculated to be 0.13 min^(-1) within 40 min, indicating a highly efficient catalytic ability of MoP. In addition, this catalyst exhibits a stable structure and good activity, which could apply in a broad pH range, different ions solution and real wastewater condition. Accordingly, this efficient catalytic capability may be attributed to the presence of the metal sites Mo^(δ+) and the electron-rich sites P^(δ-) in MoP, which could induce the generation of hydroxyl radical (^(·)OH) and superoxide radical (^(·)O_(2)^(-)) through electron transfer, resulting in the effective removal of DCF. This study provides an idea for the optimization of Fenton-like technologies and environmental remediation.

Single-phase La_(0.8)Sr_(0.2)Co_(1-x)Mn_(x)O_(3-δ) electrocatalyst as a triple H^(+)/O^(2-)/e^(-) conductor enabling high-performance intermediate-temperature water electrolysis

Hydrogen,especially the“green hydrogen”based on water electrolysis,is of great importance to build a sustainable society due to its high-energy-density,zero-carbon-emission features,and wide-range applications.Today's water electrolysis is usually carried out in either low-temperature(<100℃),e.g.,alkaline electrolyzer,or high-temperature(>700℃)applications,e.g.,solid oxide electrolyzer.However,the low-temperature devices usually suffer from high applied voltages(usually>1.5 V@0.01 A cm^(-2))and high cost;meanwhile,the high-temperature ones have an unsatisfied lifetime partially due to the incompatibility among components.Reasonably,an intermediate-temperature device,namely,proton ceramic cell(PCC),has been recently proposed.The widely-used air electrode for PCC is based on double O^(2-)/e^(-)conductor or composited O^(2-)/e^(-)-H^(+)conductor,limiting the accessible reaction region.Herein,we designed a single-phase La_(0.8)Sr_(0.2)Co_(1-x)Mn_(x)O_(3-δ)(LSCM)with triple H^(+)/O^(2-)/e^(-)conductivity as the air electrode for PCCs.Specifically,the La_(0.8)Sr_(0.2)Co_(0.8)Mn_(0.2)O_(3-δ)(LSCM8282)incorporates 5.8%proton carriers in molar fraction at 400℃,indicating superior proton conducting ability.Impressively,a high current density of 1580 mA cm^(-2) for hydrogen production(water electrolysis)is achieved at 1.3 V and 650℃,surpassing most low-and high-temperature devices reported so far.Meanwhile,such a PCC can also be operated under a reversible fuel cell mode,with a peak power density of 521 mW cm^(-2) at 650℃.By correlating the electrochemical performances with the hydrated proton concentration of single-phase triple conducting air electrodes in this work and our previous work,a principle for rational design of high-performance PCCs is proposed.