Tuning the reversible chemisorption of hydroxyl ions to promote the electrocatalysis on ultrathin metal-organic framework nanosheets

Interfacial engineering to alter the configuration of active sites in heterogeneous catalysts is a potential strategy for activity enhancement,but it remains unelucidated for metal-organic frameworks(MOFs).Here,we demonstrate that the surface of two-dimensional Co-based MOF is modified by decorating Ag quantum dots(QDs)simply through in-situ reduction of Ag+ions.Toward oxygen evolution reaction(OER),it reveals that the catalysis is mediated by the reversible redox of Co sites between Co^(3+) and Co^(4+) states coupling with transfer of OHions.The decoration of Ag QDs decreases the redox potential of Co sites,and thus effectively decreases the overpotential of OER.The TOFs of Co sites are increased by 77 times to reach 5.4 s^(-1) at an overpotential of 0.35 V.We attribute the activity enhancement to the tuning of the coupling process between Co sites and OHions during the redox of Co sites by Ag QDs decoration based on Pourbaix analysis.

Layered Trichalcogenidophosphate:A New Catalyst Family for Water Splitting

Due to the rapidly increasing demand for energy and environmental sustainability, stable and economical hydrogen production has received increasing attention in the past decades. In this regard, hydrogen production through photo-or electrocatalytic water splitting has continued to gain ever-growing interest. However, the existing catalysts are still unable to fulfill the demands of highefficiency, low-cost, and sustainable hydrogen production.Layered metal trichalcogenidophosphate(MPQ_3) is a newly developed two-dimensional material with tunable composition and electronic structure. Recently, MPQ_3 has been considered a promising candidate for clean energy generation and related water splitting applications. In this minireview, we firstly introduce the structure and methods for the synthesis of MPQ_3 materials. In the following sections, recent developments of MPQ_3 materials for photo-and electrocatalytic water splitting are briefly summarized. The roles of MPQ_3 materials in different reaction systems are also discussed. Finally, the challenges related to and prospects of MPQ_3 materials are presented on the basis of the current developments.

Graphene-supported bimetal phosphorus trisulfides as novel 0D–2D nanohybrid for high rate Li-ion storage

Herein, we report on the synthesis and Li-ion storage properties of the 0D–2D nanohybrid consisted of bimetal phosphorus trisulfides nanoneedles（Co_（0.5）Ni_（0.5）PS_3） and graphene nanosheets（denoted as Co_（0.5）Ni_（0.5）PS_3@G）. By choosing the Co_（0.5）Ni_（0.5）（OH）_2 nanoneedles as precursor, the Co_（0.5）Ni_（0.5）PS_3 derived by a simple solid-state transformation（SST） process was successfully attached onto the graphene surface.The as-prepared nanohybrids showed a superior cycling stability and rate performance for Li-ion storage.After cycling at a current density of 0.5 A g^（-1） for 500 cycles, the capacity are 456 mAh g^（-1）. Particularly,the capacity can reach 302 mAh g^（-1） at a current density of 10 A g^（-1）, which is 66.2% of the capacity at0.5 A g^（-1）. Even cycling at a current density of 50 A g^（-1）, the nanocomposite can still kept a capacity of 153 mAh g^（-1） with a capacity retention of 33.6%.

Co/Zn-metal organic frameworks derived functional matrix for highly active amorphous Se stabilization and advanced lithium storage

Lithium-selenium batteries,as an advanced rechargeable battery system,have attracted wide attention.However,its application is hurdled by the ambiguous underlying mechanism such as the unclear active phase and the key role of the host materials.Herein,a three-dimensional(3D) functional matrix derived from the Co/Znmetal organic framework is synthesized to unravel the questions raised.It reveals that the strong interaction and voids in the 3D matrix serve to anchor the amorphous Se with high electrochemical properties.The obtained 3DC/Se exhibits 544.2 and 273.2 mAh·g^(-1) t current densities of 0.1C and 2.0C,respectively,with a diffusion-controlled mechanism.The excessive amount of Se beyond the loading capacity of the matrix leads to the formation of trigonal phase Se,which shows an unsatisfying electrochemical property.

Ni nanoparticles anchoring on vacuum treated Mo_(2)TiC_(2)T_(x) MXene for enhanced hydrogen evolution activity

MXenes with metal nanoparticles(NPs)immobilized on their surface are greatly desired for high-performance electrocatalysts,while the homogeneous nucleation and growth of NPs are still challenging.Herein,a new method has been proposed for uniformly anchoring Ni NPs on the altered surficial MXene.The pre-vacuum treatment on Mo_(2)TiC_(2)T_(x)(oMX)not only removes the surficial terminal groups but also induces surface oxidation defects.Meanwhile,the nucleation and growth behaviors of Ni NPs on the oMX are altered in the hydrothermal reaction,which results in a grain-size reduction of more than 50%as well as homogeneous coverage.Eventually,the oxidized surface contributes a strong coupling between oMX and Ni NPs via Ni−O binging,which endows the Ni@oMX hybrid with the lowest overpotential and high durability over 75 h in 1 M KOH solution for electrocatalytic hydrogen evolution reaction(HER).

V4C3Tx MXene:A promising active substrate for reactive surface modification and the enhanced electrocatalytic oxygen evolution activity

Presented are the synthesis,characterizations,and reactive surface modification(RSM)of a novel nine atomic layered V4C3Tx MXene.With the advantages of the multilayered V4C3Tx MXene that can simultaneously support the RSM reaction and keep the inner skeleton stable,a series of amorphous Ni/Fe/Vternary oxide hydroxides thin layer can be successfully modified on the surface of the V4C3Tx MXene(denoted as MOOH@V4C3Tx,M=Ni,Fe,and V)without disrupting its original structure.Attributed to the in situ reconstruction of highly active oxide hydroxide layer,the nanohybrids exhibited an enhanced oxygen evolution reaction(OER)activity and excellent long-time stability over 70 hours.In particular,a current density of 10 mA cm−2 can be reached by the nanohybrid with the optimized Ni/Fe ratio at an overpotential(η)as low as 275.2 mV,which is comparable to most of the state-of-the-art OER catalysts and better than other MXene-based derivatives.Demonstrated by the tunable physicochemical properties and excellent structural stability of these nanohybrids,we may envision the promising role of the M4X3-based MXenes as substrates for a wide range of energy conversion and storage materials.