Hollow Ni Mo-based nitride heterojunction with super-hydrophilic/aerophobic surface for efficient urea-assisted hydrogen production

Hydrogen evolution reaction(HER)and urea oxidation reaction(UOR)are key reactions of the watercycling associated catalytic process/device.The design of catalysts with a super-hydrophilic/aerophobic structure and optimized electron distribution holds great promise.Here,we have designed a threedimensional(3D)hollow Ni/NiMoN hierarchical structure with arrayed-sheet surface based on a onepot hydrothermal route for efficient urea-assisted HER based on a simple hydrothermal process.The Ni/NiMoN catalyst exhibits super-hydrophilic/aerophobic properties with a small droplet contact angle of 6.07°and an underwater bubble contact angle of 155.7°,thus facilitating an escape of bubbles from the electrodes.Density functional theory calculations and X-ray photoelectron spectroscopy results indicate the optimized electronic structure at the interface of Ni and NiMoN,which can promote the adsorption/desorption of reactants and intermediates.The virtues combining with a large specific surface area endow Ni/NiMoN with efficient catalytic activity of low potentials of 25 mV for HER and 1.33 V for UOR at10 mA cm^(-2).The coupled HER and UOR system demonstrates a low cell voltage of 1.42 V at 10 mA cm^(-2),which is approximately 209 mV lower than water electrolysis.

Pt single atoms in oxygen vacancies boost reverse water-gas shift reaction by enhancing hydrogen spillover

The construction of synergistic catalysis of single atom catalysts(SACs)and oxygen vacancies(OV)on supports is crucial for the enhancement of heterogeneous catalytic efficiency,yet presents considerable challenges.Herein,we have developed an amine-molecule-assisted in-situ anchoring strategy that effectively stabilizes Pt SACs on OV sites of reduced TiO_(2)(TiO_(2)–x)by controlling the interaction of amine with Pt species and TiO_(2)–x.Direct evidence indicates that Pt SACs are anchored on the OV with forming Ptδ+–OV–Ti3+sites and strong metal-support interaction,which not only prevents the sintering of Pt SACs under high-temperature reduction treatments,but also enhances the hydrogen spillover process to facilitate the formation of more OV sites.During the reverse water-gas shift(RWGS)reaction,the enhanced amount of OV sites can increase CO_(2)adsorption,while the Pt SACs can efficiently promote the activation and spillover of hydrogen.Their combined synergistic effects greatly improve its catalytic performance with a high turnover frequency(TOF)of 9289 h−1 at 330℃ and notable stability for over 200 h,surpassing those of Pt clusters and nanoparticles on TiO_(2)–x.This work provides a new avenue for the controllable synthesis of synergistic catalysts with SACs and OV,significantly advancing catalytic efficiency.

Porous S-doped carbon nitride foam with accelerated charge dynamics for synchronous photocatalytic hydrogen production and highly selective oxidation of amines

Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-valueadded chemicals,but it is hampered by sluggish charge dynamics and limited redox potential.Herein,a porous S-doped carbon nitride(S-C_(3)N_(4−y))foam assembled from ultrathin nanosheets with rich nitrogen vacancies was synthesized using a molecular selfassembly strategy.The S dopants and N vacancies synergistically adjusted the band structure,facilitating light absorption and enhancing the oxidation ability.Moreover,the ultrathin nanosheets and porous structure provided more exposed active sites and facilitated mass and charge transfer.Consequently,S-C_(3)N_(4−y) foam exhibited enhanced photocatalytic activities for synchronous hydrogen evolution(4960μmol/(h·g))and benzylamine oxidation to N-benzylidenebenzylamine(4885μmol/(h·g))with high selectivity of>99%,which were approximately 17.6 and 72.9 times higher than those of bulk CN,respectively.The photocatalytic coupling pairing reaction promotes the water splitting by consuming H2O2,thereby improving the hydrogen evolution efficiency and achieving the production of high value-added imines.This study provides an effective route for regulating the morphology and band structure of carbon nitride for synthesizing highly valuable chemicals.

Synergistic Ru/RuO_(2) heterojunctions stabilized by carbon coating as efficient and stable bifunctional electrocatalysts for acidic overall water splitting

The development of highly active and stable acidic water oxidation electrocatalysts is of great significant for promoting the industrial application of proton exchange membrane electrolyzers.Ru-based catalysts have broad application prospects in acidic water oxidation,but their limitations in stability and activity hinder their further application.Herein,a nitrogen-doped carbon(NC)coated porous Ru/RuO_(2) heterojunctional hollow sphere(Ru/RuO_(2)/NC)is designed as high-active and stable bifunctional electrocatalyst for acidic oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).In synthesis,the key is to use mesoporous polydopamine spheres as a template for forming hollow spheres,a source of NC coating and a reducing agent for forming Ru/RuO_(2) heterojunction.The Ru/RuO_(2) heterojunction adjusts the electronic structure of Ru active sites,optimizing the adsorption of intermediate species.Furthermore,the NC coating and the interaction between NC and Ru/RuO_(2) effectively prevent Ru from over-oxidation and dissolution.The porous hollow structure provides more exposed active sites and promotes mass transfer.Impressively,Ru/RuO_(2)/NC exhibits outstanding OER and HER performance with low overpotentials of 211 and 32 mV at 10 mA·cm^(−2),respectively,and shows excellent stability.The acid water splitting electrolyzer,based on the bifunctional Ru/RuO_(2)/NC,requires low cell voltages of 1.46 and 1.76 V at 10 and 100 mA·cm^(−2),respectively,with good stability for over 100 h operation,surpassing Pt/C||RuO_(2) and most of the reported catalysts.

Few-layered MoS_(2)anchored on 2D porous C_(3)N_(4)nanosheets for Ptfree photocatalytic hydrogen evolution

The Pt-free photocatalytic hydrogen evolution(PHE)has been the focus in the photocatalytic field.The catalytic system with the large accessible surface and good mass-transfer ability,as well as the intimate combination of co-catalyst with semiconductor is promising for the promotion of the application.Here,we have reported the design of the two-dimensional(2D)porous C_(3)N_(4)nanosheets(PCN NS)intimately combined with few-layered MoS_(2)for the high-effective Pt-free PHE.The PCN NS were synthesized based on peeling the melamine–cyanuric acid precursor(MC precursor)by the triphenylphosphine(TP)molecular followed by the calcination,mainly due to the matched size of the(100)plane distance of the precursor(0.8 nm)and the height of TP molecular.The porous structure is favorable for the mass-transfer and the 2D structure having large accessible surface,both of which are positive to promote the photocatalytic ability.The few-layered MoS_(2)are grown on PCN to give 2D MoS_(2)/PCN composites based on anchoring phosphomolybdic acid(PMo_(12))cluster on polyetherimide(PEI)-modified PCN followed by the vulcanization.The few-layered MoS_(2)have abundant edge active sites,and its intimate combination with porous PCN NS is favorable for the faster transfer and separation of the electrons.The characterization together with the advantage of 2D porous structure can largely promote the photocatalytic ability.The MoS_(2)/PCN showed good PHE activity with the high hydrogen production activity of 4,270.8μmol·h^(−1)·g^(−1)under the simulated sunlight condition(AM1.5),which was 7.9 times of the corresponding MoS_(2)/bulk C_(3)N_(4)and 12.7 times of the 1 wt.%Pt/bulk C_(3)N_(4).The study is potentially meaningful for the synthesis of PCN-based catalytic systems.

The“mediated molecular”-assisted construction of Mo_(2)N islands dispersed on Co-based nanosheets for high-efficient electrocatalytic hydrogen evolution reaction

The rational design of the catalysts with easily-accessible surface and high intrinsic activity is desirable for electrocatalytic hydrogen evolution reaction(HER).Here,we reported the construction of two-dimensional(2D)Co-Mo nitrides based heterojunctional catalyst for efficient HER based on a“mediated molecular”assisted route.The 2D Co(OH)_(2)sheet reacted partially with the“mediated molecular”(2-methylimidazole(2-MIM))to form zeolitic imidazolate framework(ZIF)-67 at surface,giving ZIF-67/Co(OH)_(2)sheets.The ZIF-67 combines with[PMo_(12)O_(40)]^(3−)cluster(PMo_(12))due to the interaction of mediated molecular with PMo_(12),producing 2D Mo-Co-2MIM/Co(OH)_(2)bimetallic precursor.After controlled nitriding,the Mo_(2)N islands dispersed on 2D porous Co-based sheets were formed.A series of characterizations and density functional theory(DFT)calculation indicated the formation of a close contact interface,which promotes the electron transfer between Mo and Co components,enhances the electron migration/redistribution and redistribution and down-shift of d-band center and thus gives a high intrinsic activity.The 2D characteristics make the catalyst more accessible contact sites,which is favourable to promot the HER.The tests showed that the optimized catalyst exhibits an onset potential of 0 mV and an overpotential of 10 mA·cm^(−2)at 35.0 mV,which is quite close to that of Pt/C catalyst.It also exhibits an activity superior to Pt/C at high current density(>100 mA·cm^(−2)).A good stability of the catalyst was achieved with no significant decay for 100 h of continuous operation.The electrolytic cell composed of optimized catalyst and P-NiFe-layered double hydroxide(LDH)can be driven by low voltage(only 1.47 V)to reach a current density of 10 mA·cm^(−2).

Recent progress in synergistic electrocatalysis for generation of valuable products based on water cycle

Given the grim situation of global warming and energy crisis,replacing traditional energy conversions based on carbon cycle with water cycle is a sustainable development trend.The synergistic electrocatalysis for value-added chemical production through oxygen species(O_(ads):OH^(*),O^(*),and OOH^(*))and the active hydrogen species(H_(ads))derived from water splitting powered by“green”electricity from renewable energy resource(wind,solar,etc.)is a promising manner,because of its reduced energy consumption and emission and high Faradaic efficiency.The study and summarization of catalytic mechanism of synergistic electrocatalysis are particularly significant,but are rarely involved.In this review,recent progress of various synergistic electrocatalysis systems for generating valuable products based on water cycle is systematically summarized.Importantly,the catalytic mechanism of synergistic electrocatalysis and the positive effect of O_(ads) and H_(ads) species produced by water splitting during the synergistic electrocatalytsis are detailedly elucidated.Furthermore,the regulation of water-derived O_(ads) and H_(ads) species for achieving efficient matchability of synergistic electrocatalysis is emphatically discussed.Finally,we propose the limitations and future goals of this synergistic system based on water cycle.This review is guidance for design of synergistic electrocatalysis architectures for producing valuable substances based on water cycle.

Tuning electronic structure of Ni_(3)S_(2) with tungsten doping for high-performance electrooxidation of 5-hydroxymethylfurfural

Electrooxidation of the biomass derivative 5-hydroxymethylfurfural (HMF) is a highly promising approach for attaining versatile value-added chemicals (e.g.,2,5-furandicarboxylic acid,FDCA).Ni-based sulfides are promising electrocatalysts for HMF electrooxidation reaction (HMFOR).However,the HMFOR activity of Ni-based catalysts is far from satisfactory due to the unfavorable adsorption of HMF and OH^(*).Herein,we propose controlled W doping to effectively modify the electronic configuration of nanostructured Ni_(3)S_(2) to manipulate adsorption of HMF and OH^(*),for efficiently converting HMF into FDCA.Experimental and theoretical calculations indicate the incorporation of high-valence W results in the upshift of d-band center of Ni_(3)S_(2),which facilitates the adsorption and dissociation of water to produce more OH^(*).Meanwhile,the high-valence W has strong electron-withdrawing ability and attracts electrons from Ni,leading to the elevated Ni valence,which is beneficial to optimizing the adsorption energy of HMF.Both concurrently contribute to the superb HMFOR performance.As a result,W_(20)-Ni_(3)S_(2)@NF with optimal W dopant exhibits a low driving potential (1.34 V vs.RHE at 10 mA cm^(-2)),accompanying with the 100% HMF conversion,99.2%FDCA selectivity,and 97.3%Faraday efficiency.This work provides a design principle for HMFOR electrocatalysts by modulating the adsorption behaviors of HMF and OH^(*)via rational electronic structure engineering.

Two-dimensional porous Cu-CuO nanosheets: Integration of heterojunction and morphology engineering to achieve high-effective and stable reduction of the aromatic nitro-compounds

The morphology and heterojunction engineering are effective ways to boost the performance of Cubased catalysts. Herein, we have reported the designed synthesis of two-dimensional Cu-Cu O heterojunction nanosheets(2D Cu-Cu O NS) based on 3-aminopropyl-triethoxysilane(APTES, KH550) aided synthetic strategy. The APTES can act as both the ligand and alkali(-OH) source to guide the large-scale synthesis of 2D Cu-based precursor, which can transform into 2D Cu-Cu O NS by the controllable post-treatment.The Si species from APTES can protect the particles from the severe aggregation and growth, guaranteeing the formation of 2D sheets composed of small-sized Cu-Cu O heterojunction(about 20 nm). The heterojunction interfaces can provide plentiful active sites to boost the catalytic ability. The 2D sheets can provide large accessible surface, being conducive to the contact of the catalyst and reactants. Benefiting from above virtues, the 2D Cu-Cu O NS showed the superior catalytic performance for the reduction of a series of nitro compounds, being superior to most reported non-noble metal-based catalysts. Notably,it exhibited good re-cycled performance with no obvious performance degradation after 10 consecutive catalysis. The present study will be promising to promote the application of the Cu-based catalysts, due to its ability to control the morphology and potential for the large-scale synthesis.

Morphological and heterojunctional engineering of two-dimensional porous Mo-Ni based catalysts for highly effective catalytic reduction of aromatic nitro compounds

Hydrogenation reactions play crucial roles on chemical synthesis and pollutant elimination.The improvement of the ability to activate reactants and increase of the contact probability between the catalysts and reactants are positive to improve the catalytic performance.Herein,we have reported the design of two-dimensional porous Ni-Ni_(3)N-Ni Mo N heterojunction sheets(2D Mo-Ni based nanosheets)for efficient catalytic hydrogenation of the aromatic nitro-compounds.The heterojunction interfaces provide plentiful active sites to improve the activating ability of the catalyst on the reactants.Additionally,the 2D porous structure facilitates not only the contact of catalytic sites with reactants but also mass transfer and diffusion,both of which are favorable to accelerating the hydrogenation process.As a result,the optimized sample of 2D Mo-Ni sheet exhibits good activity for the hydrogenation of aromatic nitro-compounds by converting 0.2 mmol/L(30 mL)of p-nitrophenol to p-aminophenol within 45 s with good recyclability.The activation energy and the reaction rate at 25℃ is 31.11 k J/mol and 0.0796 s^(-1),respectively,both of which surpass most of reported non-noble metal catalysts and rivals with most noble metal-based catalysts.The combination of late and early transition metals provides an innovative way to obtain outstanding catalysts for the hydrogenation.

Synchronous regulation of morphology and electronic structure of FeNi-P nanosheet arrays by Zn implantation for robust overall water splitting

FeNi-based phosphides are one of the most hopeful electrocatalysts,whereas the significant challenge is to achieve prominent bifunctional catalytic activity with low voltage for water splitting.The morphology and electronic structure of FeNi-based phosphides can intensively dominate effective catalysis,therefore their simultaneous regulating is extremely meaningful.Herein,a robust bifunctional catalyst of Zn-implanted FeNi-P nanosheet arrays(Zn-FeNi-P)vertically well-aligned on Ni foam is successfully fabricated by Zn implanting strategy.The Zn fulfills the role of electronic donor due to its low electronegativity to enhance the electronic density of FeNi-P for optimized water dissociation kinetics.Meanwhile,the implantation of Zn into FeNi-P can effectively regulate morphology of the catalyst from thick and irregular nanosheets to ultrathin lamellar structure,which generates enriched catalytic active sites,leading to accelerating electron/mass transport ability.Accordingly,the designed Zn-FeNi-P catalyst manifests remarkable hydrogen evolution reaction(HER)activity with low overpotentials of 55 and 225 mV at 10 and 200 mA·cm^(−2),which is superior to the FeNi-P(82 mV@10 mA·cm^(−2)and 301 mV@200 mA·cm^(−2)),and even out-performing the Pt/C catalyst at a high current density>200 mA·cm^(−2).Moreover,the oxygen evolution reaction(OER)activity of Zn-FeNi-P also has dramatically improved(207 mV@10 mA·cm^(−2))comparable to FeNi-P(221 mV@10 mA·cm^(−2))and RuO_(2)(239 mV@10 mA·cm^(−2)).Noticeably,an electrolyzer based on Zn-FeNi-P electrodes requires a low cell voltage of 1.47 V to achieve 10 mA·cm^(−2),far beyond the catalytic activities of FeNi-P||FeNi-P(1.51 V@10 mA·cm^(−2))and the benchmark RuO_(2)||Pt/C couples(1.56 V@10 mA·cm^(−2)).This Zn-implanting strategy paves a new perspective for the development of admirable bifunctional catalysts.

Small-sized tungsten nitride anchoring into a 3D CNT- rGO framework as a superior bifunctional catalyst for the methanol oxidation and oxygen reduction reactions

The application of direct methanol fuel cells （DMFC） is hampered by high cost, low activity, and poor CO tolerance by the Pt catalyst. Herein, we designed a fancy 3D hybrid by anchoring tungsten nitride （WN） nanoparticles （NPs）, of about 3 nm in size, into a 3D carbon nanotube-reduced graphene oxide framework （CNT-rGO） using an assembly route. After depositing Pt, the contacted and strongly coupled Pt-WN NPs were formed, resulting in electron transfer from Pt to WN. The 3D Pt-WN/CNT-rGO hybrid can be used as a bifunctional electrocatalyst for both methanol oxidation reaction （MOR） and oxygen reduction reaction （ORR）. In MOR, the catalysts showed excellent CO tolerance and a high mass activity of 702.4 mA.mgpt-1, 2.44 and 3.81 times higher than those of Pt/CNT-rGO and Pt/C（JM） catalysts, respectively. The catalyst also exhibited a more positive onset potential （1.03 V）, higher mass activity （151.3 mA.mgpt-1）, and better cyclic stability and tolerance in MOR than ORR. The catalyst mainly exhibited a 4e-transfer mechanism with a low peroxide yield. The high activity was closely related to hybrid structure. That is, the 3D framework provided a favorable path for mass-transfer, the CNT-rGO support was favorable for charge transfer, and strongly coupled Pt-WN can enhance the catalytic activity and CO-tolerance of Pt. Pt-WN/CNT-rGO represents a new 3D catalytic platform that is promising as an electrocatalyst for DMFC because it can catalyze both ORR and MOR in an acidic medium with good stability and highly efficient Pt utilization.

Surface curvature-confined strategy to ultrasmall nickel-molybdenum sulfide nanoflakes for highly efficient deep hydrodesulfurization

Size-controlled synthesis of two-dimensional(2D)catalysts with low stacking numbers and small nanoflake lengths is crucial for promoting the catalytic performance in diverse heterogeneous catalysis.Herein,we report a facile and general“surface curvature-confined synthesis”strategy to modulate the slab lengths and stacking numbers of 2D transition metal sulfides by controlling the strain induced by different surface curvature of supports.An efficient NiMo sulfide with shorter slab length(average 3.71 nm),less stacking number(1–2 layers)and more edge active sites is synthesized onto ZSM-5 zeolites with the average size of 100 nm,which shows superior kHDS value of dibenzothiophene(14.05×10^−7 mol/(g·s)),enhanced stability up to 80 h,and high direct desulfurization selectivity(>95%).This design concept is also proved to be generally applicable to modulate the slab lengths and stacking numbers of other 2D catalysts such as MoS2 and WS2 nanoflakes,which shows great potentials for developing more ultrasmall 2D catalysts with controlled sizes and excellent catalytic activities.

Nitrogen-doped graphene supported Pd@PdO core- shell clusters for C-C coupling reactions

The introduction of nitrogen significantly decreases the metal particle size and improves the performance of metal-based graphene-supported catalysts. In this work, the density functional theory is used to understand the interaction between nitrogen-doped graphene and Pd@PdO clusters. Experiments show that small size Pd@PdO clusters （1-2 nm） can be grown uniformly on nitrogen-doped graphene sheets by a facile oxidation-reduction method. The nanoscale interaction relationship between nitrogen-doped graphene and Pd@PdO clusters is investigated through X-ray photoelectron spectroscopy （XPS） and X-ray absorption spectra （XAS）. The composite catalysts are applied in Suzuki-Miyaura reactions giving high yields and good structural stability. These results have potential impact in design and optimization of future high performance catalyst materials for cross coupling reactions.

A dual-active Co-CoO heterojunction coupled with Ti_(3)C_(2)-MXene for highly-performance overall water splitting

Development of cost-effective and highly-efficient bifunctional hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalysts is crucial for overall water splitting in practical utilization.Herein,we proposed a novel non-noble metal bifunctional,HER/OER electrocatalyst by synergistically coupling a dual-active Co-based heterojunction(Co-CoO)with high conductive and stable two-dimensional Ti_(3)C_(2)-MXene(defined as Co-CoO/Ti^(3)CrMXene).A series of characterizations and theoretical calculations'verify that the synergistic effect of metallic Co with HER activity and Coo with OER performance leads to superb bifunctional catalytic performance,and Ti_(3)C_(2)-MXene can enhance electrical conductivity and prevent the aggregation of the Co-based catalysts,thereby improving both the activity arid stability.Co-Co0/Ti_(3)C_(2)-MXene presents low onset potential(11onse1)of 8 mV and,Tafel slope of 47 mV·dec^(-1) for HER(close to that of Pt/C)and 17onset of 196 mV and Tafel slope of 47 mV·dec^(-1) for OER(superior to:that of Ru02).Assembled as an electrolyzer,Co-CoO/Ti_(3)C_(2)-MXene shows a low voltage of 1.55 V at 10 mA·cm^(-2),high Faradaic efficiency and remarkable stability.It can be driven by a solar cell of-1.55 V for consecutive production of hydrogen and oxygen gases.

From graphite to porous graphene-like nanosheets for high rate lithium-ion batteries

Graphene nanosheets possess a promising potential as electrodes in Li-ion batteries （LIBs）; consequently, the development of low-cost and high-productivity synthetic approaches is crudal. Herein, porous grapheneqike nanosheets （PGSs） have been synthesized from expandable graphite （EG） by initially intercalating phosphoric acid, and then performing annealing to enlarge the interlayer distance of EG, thus fadlitating the successive intercalation of zinc chloride. Subsequently, the following pyrolysis of zinc chloride in the EG interlayer promoted the formation of the porous PGS structure; meanwhile, the gas produced during the formation of the porous structure could exfoliate the EG to graphene-like nanosheets. The synthetic PGS material used as LIB anode exhibited superior Li＋ storage performance, showing a remarkable discharge capacity of 830.4 mAh.g-1 at 100 mA.g-1, excellent rate capadty of 211.6 mAh＇g-1 at 20,000 mA-g-1, and excellent cycle performance （near 100% capacity retention after 10,000 cycles）. The excellent rate performance is attributed to the Li＋ ion rapid transport in porous structures and the high electrical conductivity of graphene-like nanosheets. It is expected that PGS may be widely used as anode material for high-rate LIBs via this facile and low-cost route by employing EG as the raw material.

Porous NiCoP nanowalls as promising electrode with high-area and mass capacitance for supercapacitors

The design of the electrode with high-area and mass capacitance is important for the practical application of supercapacitors. Here, we fabricated the porous NiCoP nanowalls supported by Ni foam(NiCo-P/NF) for supercapacitors with win-win high-area and mass capacitance. The NiCoOH nanowall precursor was prepared by controlling the deposition rate of Ni^2+ and Co^2+ on NF through a sodium acetate-assisted(floride-free) process. After the phosphorization, the NiCo-P nanowalls formed with high loading about8.6 mg cm-2 on NF. The electrode combined several advantages favorable for energy storage: the plentiful pores beneficial for ion transport, the nanowalls for easy accommodation of electrolyte, good conductivity of NiCo-P for easy transport of electrons. As expected, the NiCo-P/NF exhibited a high specific mass capacitance(1,861 F g^-1 at 1 A g^-1,1,070 F g^-1 at 10 A g^-1 and high area capacitance(17.31 F cm-2 at 5 mA cm-2 and 10 F cm^-2 at 100 mA cm^-2.The asymmetric supercapacitor(ASC) composed of NiCo-P/NF positive electrode coupled with commercial active carbon negative electrode exhibited a high energy density of44.9 W h kg^-1 at a power density of 750 W kg^-1. The ASC can easily drive fans, electronic watch and LED lamps, implying their potential for the practical application.

One-dimensional Co_(9)S_(8)-V_(3)S_(4)heterojunctions as bifunctional electrocatalysts for highly efficient overall water splitting

Development of cost-effective,active and durable electrocatalysts for overall water splitting is still a huge challenge.Herein,we have constructed one-dimensional(1D)cobalt sulfide and vanadium sulfide heterojunction nanowires arranged on carbon cloth(Co_(9)S_(8)-V_(3)S_(4)/CC)as bifunctional electrocatalysts for the efficient overall water splitting.The 1D wire-structured Co_(9)S_(8)-V_(3)S_(4)heterojunctions possess large surface area,plentiful active sites and rapid transport of electrons/reactants and the release of gas.Importantly,the electron transfer from Co9S8 to V3S4 occurs at the interface due to the strong electronic coupling effect in Co_(9)S_(8)-V_(3)S_(4)heterojunction,in which the electron-attracting V3S4(V2^(+))optimizes the adsorption of H*active species for hydrogen evolution reaction(HER),while the electron-losing Co9S8(Co3+)responds to the enhancement of oxygen evolution reaction(OER)activity.Co_(9)S_(8)-V_(3)S_(4)/CC exhibits low overpotentials of 85 and 232 mV at 10 mA cm^(−2)and small Tafel slopes of 51 and 59 mV dec^(−1)for HER and OER,respectively.Especially,the electrolyzer with Co_(9)S_(8)-V_(3)S_(4)/CC as both the anode and cathode requires low onset voltage of 1.35 V and cell voltage of 1.53 V at 10 mA cm^(−2)and exhibits high Faradaic efficiencies and robust stability.It can be driven by a solar cell(1.53 V)for continuous production of hydrogen and oxygen.This study highlights the design of 1D sulfide heterojunction in pursuit of highly efficient electrocatalysts for overall water splitting.

Cubic imidazolate frameworks-derived CoFe alloy nanoparticles-embedded N-doped graphitic carbon for discharging reaction of Zn-air battery

The construction of transition metal-based catalysts with high activity and stability has been widely regarded as a promising method to replace the precious metal Pt for oxygen reduction reaction(ORR).Herein,we synthesized CoFe alloy nanoparticle-embedded N-doped graphitic carbon(CoFe/NC)nanostructures as ORR electrocatalysts.The ZIF-67(zeolitic imidazolate framework,ZIF)nanocubes were first synthesized,followed by an introduction of Fe2+ions to form CoFe-ZIF precursors via a simple ion-exchange route.Subsequently,the CoFe/NC composites were synthesized through a facile pyrolysis strategy.The ORR activity and the contents of cobalt and iron could be effectively adjusted by controlling the solution concentration of Fe2+ions used for the ion exchange and the pyrolysis temperature.The CoFe/NC-0.2-900 composite(synthesized with 0.2 mmol of FeSO4·7H2O at a pyrolysis temperature of 900℃)exhibited ORR activity that was superior to the other samples owing to a synergistic effect of the bimetal,especially considering the extremely high limiting current density of 6.4 mA cm^-2 compared with that of Pt/C(5.1 mA cm^-2).Rechargeable Zn-air batteries were assembled employing CoFe/NC-0.2-900 and NiFeP/NF(NiFeP supported on nickel foam(NF))as the catalysts for the discharging and charging processes,respectively,The above materials achieved reduced discharging and charging platforms,high power density,and prolonged cycling stability compared with conventional Pt/C+RuO2/C catalysts.