钴钒水滑石纳米片用于电催化尿素氧化

电解水是一种常用的制氢方法,但高能耗的阳极析氧反应(OER)阻碍了其应用。尿素氧化反应(UOR)具有较低的热力学电势,是最有前景的OER替代反应之一。过渡金属基水滑石具有独特的层状结构和层间阴离子可交换等优点,被认为是性能优异的UOR催化剂,然而目前大多数研究主要聚焦于后过渡金属元素。该研究通过一步法制备了具有前/后过渡金属的CoV-LDHs纳米片。与相同方法制备的Co(OH)_(2)相比,CoV-LDHs纳米片具有以下优点:1)纳米片结构有利于暴露更多的活性位点。2)V的引入增强了CoV-LDHs的亲水性,提高了其本征电催化动力学。3)Co(3d^(7)4s^(2))和V(3d^(3)4s^(2))之间的d-电子补偿效应有利于促进尿素的吸附。因此,CoV-LDHs仅需要1.52 V(vs.RHE)就可以达到10 mA·cm^(−2)的电流密度,比Co(OH)_(2)低了70 mV,同时CoV-LDHs较低的塔菲尔斜率表明了其较快的反应动力学。此外,CoV-LDHs在连续反应10 h后,驱动电位几乎没有增加,表明其具有良好的稳定性。该研究结果不仅证明了前/后过渡金属之间的d-电子补偿效应可以提高UOR催化性能,还为设计高效的UOR催化剂提供了可行的途径。

Electrodeposited 3D hierarchical NiFe microflowers assembled from nanosheets robust for the selective electrooxidation of furfuryl alcohol

A robust and green strategy for the selective upgrading of biomass-derived platform chemicals towards highly valuable products is important for the sustainable development.Herein,the efficient electrocatalytic oxidation of biomass-derived furfuryl alcohol(FFA)into furoic acid(FurAc)catalyzed by the electrodeposited non-precious NiFe microflowers was successfully reached under the low temperature and ambient pressure.The 3D hierarchical NiFe microflowers assembled from ultrathin nanosheets were controllably synthesized by the electrodeposition method and uniformly grown on carbon fiber paper(CFP).Electrochemical analysis confirmed that NiFe nanosheets more preferred in the selective oxidation of FFA(FFAOR)than oxygen evolution reaction(OER).The linear sweep voltammetry(LSV)in FFAOR displayed a clear decrease towards lower potential,resulting in 30 mV reduction of overpotential at 20 mA cm^(-2) compared with that of OER.The optimal catalyst Ni_(1)Fe_(2) nanosheets exhibited the highest selectivity of FurAc(94.0%)and 81.4%conversion of FFA within 3 h.Besides,the influence of various reaction parameters on FFAOR was then explored in details.After that,the reaction pathway was investigated and rationally proposed.The outstanding performance for FFAOR can be ascribed to the unique structure of 3D flower-like NiFe nanosheets and oxygen vacancies,resulting in large exposure of active sites,faster electron transfer and enhanced adsorption of reactants.Our findings highlight a facile and convenient mean with a promising green future,which is promising for processing of various biomass-derived platform chemicals into value-added products.

Efficient electrooxidation of biomass-derived aldehydes over ultrathin Ni V-layered double hydroxides films

Selective upgrading of C=O bonds to afford carboxylic acid is significant for the petrochemical industry and biomass utilization.Here we declared the efficient electrooxidation of biomass-derived aldehydes family over NiV-layered double hydroxides(LDHs) thin films.Mechanistic studies confirmed the hydroxyl active intermediate(-OH*) generated on the surface of NiV-LDHs films by employing electrochemical impedance spectroscopy and the electron paramagnetic resonance spectroscopy.By using advanced techniques,e.g.,extended X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy,NiV-LDHs films with 2.6 nm could expose larger specific surface area.Taking benzaldehyde as a model,high current density of 200 mA cm^(-2)at 1.8 V vs.RHE,81.1% conversion,77.6% yield of benzoic acid and 90.8% Faradaic efficiency were reached,which was superior to most of previous studies.Theoretical DFT analysis was well matched with experimental findings and documented that NiV-LDHs had high adsorption capacity for the aldehydes to suppress the side reaction,and the aldehydes were oxidized by the electrophilic hydroxyl radicals formed on NiV-LDHs.Our findings offer a universal strategy for the robust upgrading of diverse biomass-derived platform chemicals.

In situ growth of hydrophilic nickel-cobalt layered double hydroxides nanosheets on biomass waste-derived porous carbon for high-performance hybrid supercapacitors

Rational design and cost-effective fabrication of layered double hydroxides(LDHs)nanosheets with extraordinary electrochemical performance is a key challenge for hybrid supercapacitors(HSCs).Herein,we report a facile in situ growth methodology to eco-friendly synthesize hydrophilic Ni Co-LDHs nanosheets on biomass waste-derived porous carbon(BC)for robust high-performance HSC cathode.The in situ growth process under ultrasonication realizes the rational arrangement of Ni Co-LDHs nanosheets on the surface of BC,which effectively increases the specific surface area,promotes the electronic conductivity and enhances the wettability of Ni Co-LDHs nanosheets without affecting their thickness values.With the beneficial effects of ultrathin thickness of LDHs nanosheets(6.20 nm),large specific surface area(2324.1 m^(2)g^(-1)),low charge transfer resistance(1.65Ω),and high wettability with electrolyte(34°–35°),the obtained Ni2Co1-LDHs/BC50 electrode possesses an ultra-high specific capacitance of 2390 F g^(-1)(956 C g^(-1))at 1 A g^(-1),which is superior to most reported values.Furthermore,an assembled Ni_(2)Co_(1)-LDHs/BC50//YP-80F HSC delivers a maximum specific energy of 52.47 Wh kg^(-1)at375 W kg^(-1),and maintains a high capacitance retention of 75.9%even after 4000 cycles.This work provides a facile approach to fabricate LDHs nanosheets based cathode materials for high-performance HSCs.

一步法构筑双功能富含氧空位的花瓣状镍铝水滑石纳米薄片用于高性能超级电容器和尿素氧化

镍基水滑石在能量存储(超级电容器)和转化(尿素氧化)领域是很有前景的电极材料.合理构建镍基水滑石的原子和电子结构对于实现其理想的电化学性能至关重要.本论文报道了一种简单、环境友好的一步法制备富含氧空位的花瓣状镍铝水滑石(NiAl-LDHs)纳米薄片用于混合超级电容器和尿素氧化.性能最好的富氧空位NiAl-LDHs纳米薄片具有216.6 m^(2) g^(-1)的大比表面积和3.45×10^(-4)S cm^(-1)的高电导率,可在1 A g^(-1)的比电流下展示出2801 F g^(-1)(700 C g^(-1))的超高比电容.基于NiAl-LDHs//商业活性炭组装的混合超级电容器在400 W kg^(-1)比功率密度下可获得50.0 W h kg^(-1)的比能量,且循环10,000次后仍有91%的电容保持率.同时,NiAl-LDHs纳米薄片作为高效的尿素氧化电催化剂,在1 mol L^(-1)KOH和0.33 mol L^(-1)尿素中仅需1.42 V vs.可逆氢电极的氧化电位就可达到10 mA cm^(-2)的电流密度.由于NiAl-LDHs的纳米薄片结构暴露了更多的活性位点和丰富的氧空位,其电化学性能优于大部分报道的镍基水滑石.因此,本研究为多功能纳米能源材料的合理设计奠定了良好的基础.

Facile synthesis of Ni-,Co-,Cu-metal organic frameworks electrocatalyst boosting for hydrogen evolution reaction

The conductive metal-organic frameworks(MOFs)are suggested as the ideal electrocatalysts for hydrogen evolution reaction(HER)because of the high utilization of metal atoms.Rational design and facile synthesis of MOFs with large specific surface area,proper metals as center,and tunable chemical components is still full of challenges.Herein,we report the facile synthesis three types of porous MOFs by regulating metal center using benzene-1,3,5-tricarboxylic acid(H3 BTC)as organic ligand and have successfully synthesized the rhombic octahedral Cu-BTC,rod-shaped Co-BTC and spherical Ni-BTC materials with large specific surface area ranged in 350-500 m^(2)g^(-1).These as-prepared MOFs materials exhibit high performance of HER in 0.5 M H_(2)SO_(4).Ni-BTC material exhibits the lowest overpotential of 53 mV at 10 mA cm-2 and the smallest Tafel slope of 62 mV dec^(-1)than those of Cu-BTC(270 mV,155 mV dec^(-1))and Co-BTC(123 mV,100 mV dec^(-1)),which are much superior to these previously reported MOFs catalysts.In addition,the fast catalytic kinetic of Ni-BTC was confirmed by the smaller charge transfer resistance(Rct)value of 0.9Ωand larger electrochemical active surface area(ECSA)of 35.5 cm^(2)than those of Cu-BTC(8.2Ω,22.5 cm^(2))and Co-BTC(1.9Ω,27.7 cm^(2)).Because of the structural advantage and large ECSA,the turnover frequency(TOF)value of Ni-BTC reaches up to 0.041 s-1 at 120 mV overpotential,which is 20.5 and 2.6 times greater than that of Cu-BTC(0.002 s-1)and Co-BTC(0.016 s-1).Besides,these three types of MOFs exhibited excellent durability over 12 h.This study unfolds diverse insights into the design and facile synthesis of MOFs for electrochemical energy conversion system.

Bidirectional Light-Driven Ion Transport through Porphyrin Metal–Organic Framework-Based van der Waals Heterostructures via pH-Induced Band Alignment Inversion

Heterogeneous two-dimensional layered membranes reconstructed fromnatural or synthetic van derWaals materials enable novel ion transport mechanisms by coupling with the chemical and optoelectronic properties of the layered constituents.Here,we report a light-driven and pH-dependent bidirectional ion transport phenomenon through porphyrin metal–organic framework(PMOF)and transition metal dichalcogenides-based multilayer van der Waals heterostructures with sub-nanometer ionic channels.