In this paper, we have demonstrated few-layer MoS 2 doping using potassium iodide (KI) solution to realize stable/reliable ohmic contacts and achieve efficient electron transport. We have shown that ...KI doping allows MoS 2 doping with a dopant density up to <inline-formula> <tex-math notation="LaTeX">{1}\times {10}^{{12}}\,\,\text {cm}^{-{2}} </tex-math></inline-formula> near source/drain edge. The same has been explained using density-functional-theory (DFT)-based band structure calculations. KI doping of MoS 2 resulted in contact resistance reduction by <inline-formula> <tex-math notation="LaTeX">3.5\times </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">0.75\,\,\text {k} \Omega {-}\mu \text {m} </tex-math></inline-formula>). The proposed technique and improved contacts have also resulted in <inline-formula> <tex-math notation="LaTeX">2\times </tex-math></inline-formula> improvement in ON-state current (<inline-formula> <tex-math notation="LaTeX">500~\mu \text {A}/\mu \text {m} </tex-math></inline-formula>), transconductance and field-effect mobility (<inline-formula> <tex-math notation="LaTeX">70~\text {cm}^{{2}}/\text {Vs} </tex-math></inline-formula>) without compromising with OFF-state behavior, while maintaining ON to OFF ratio well above <inline-formula> <tex-math notation="LaTeX">10^{{6}} </tex-math></inline-formula>. The reproducibility of the transistor characteristics after a longer period (2 months) confirms the stability of proposed doping technique against environmental conditions.
Designing catalysts to accelerate the conversion of soluble lithium polysulfides (LiPSs) is regarded as a promising strategy to inhibit the shuttle effect, improving cathode performance of ...lithium–sulfur batteries (LSBs). Herein, a bifunctional Ni/Zn dual‐doped CoSe2 is designed to enhance the catalytic effect of CoSe2. Specifically, Ni functions better in catalyzing the conversion of LiPSs into Li2S with shorter CoS bond and longer SS bonds than Zn, while Zn demonstrates a better catalytic effect for Li2S decomposition with reduced Li2S decomposition barrier and elongated LiS bonds than Ni. Those endows Ni/Zn dual‐doped CoSe2 with bifunction in catalyzing conversion reaction of LiPSs and Li2S precipitation as well as the decomposition of Li2S, originating from the modified molecular structure of LiPSs and Li2S. As a result, the sulfur cathode with Ni0.1Zn0.1Co0.8Se2 achieves a rate capability of 681.74 mAh g–1 at 2C, and a cycling stability for 400 cycles with a decay rate of 0.065%. This work provides an effective way to improve catalytic effect of transition metal compounds for advanced LSBs by homogenous dual doping.
A bifunctional Ni/Zn dual‐doped CoSe2 is designed and used as a catalyst for lithium‐sulfur batteries, to improve the catalytic effect of CoSe2. Ni/Zn dual‐doped CoSe2 exhibits excellent catalytic effect due to bifunctional roles in catalyzing conversion reaction of lithium polysulfides (LiPSs), precipitation, and decomposition of Li2S, by combining the function of Ni and Zn.
The electrochemical nitrogen reduction reaction (e‐NRR) is envisaged as alternative technique to the Haber–Bosch process for NH3 synthesis. However, how to develop highly active e‐NRR catalysts faces ...daunting challenges. Herein, a viable strategy to manipulate local spin state of isolated iron sites through S‐coordinated doping (FeSA‐NSC) is reported. Incorporation of S in the coordination of FeSA‐NSC can induce the transition of spin‐polarization configuration with the formation of a medium‐spin‐state of Fe (t2g6 eg1), which is beneficial for facilitating eg electrons to penetrate the antibonding π‐orbital of nitrogen. As a consequence, a record‐high current density up to 10 mA cm−2 can be achieved, together with a high NH3 selectivity of ≈10% in a flow cell reactor. Both experimental and theoretical analyses indicate that the monovalent Fe(I) atomic center in the FeSA‐NSC after the S doping accelerates the N2 activation and protonation in the rate‐determining step of *N2 to *NNH.
An atomically dispersed monovalent iron(I) site with a medium‐spin state is developed to promote cleavage of the N≡N bonds and facilitate the rate‐determining step of N2 hydrogenation kinetics.
Two‐step‐fabricated FAPbI3‐based perovskites have attracted increasing attention because of their excellent film quality and reproducibility. However, the underlying film formation mechanism remains ...mysterious. Here, the crystallization kinetics of a benchmark FAPbI3‐based perovskite film with sequential A‐site doping of Cs+ and GA+ is revealed by in situ X‐ray scattering and first‐principles calculations. Incorporating Cs+ in the first step induces an alternative pathway from δ‐CsPbI3 to perovskite α‐phase, which is energetically more favorable than the conventional pathways from PbI2. However, pinholes are formed due to the nonuniform nucleation with sparse δ‐CsPbI3 crystals. Fortunately, incorporating GA+ in the second step can not only promote the phase transition from δ‐CsPbI3 to the perovskite α‐phase, but also eliminate pinholes via Ostwald ripening and enhanced grain boundary migration, thus boosting efficiencies of perovskite solar cells over 23%. This work demonstrates the unprecedented advantage of the two‐step process over the one‐step process, allowing a precise control of the perovskite crystallization kinetics by decoupling the crystal nucleation and growth process.
The whole crystallization pathways and mechanism of two‐step‐fabricated perovskites are unveiled by in situ grazing‐incidence wide‐angle X‐ray scattering measurements and density functional theory calculations. Sequential A‐site doping of Cs+ and GA+ is found to alter the crystallization kinetics and improves the perovskite film morphology, giving rise to device efficiency as high as 23.5%.
Structural design and modification are effective approaches to regulate the physicochemical properties of TiO2, which play an important role in achieving advanced materials. Herein, a plasma‐assisted ...method is reported to synthesize a surface‐defect‐rich and deep‐cation‐site‐rich S doped rutile TiO2 (R‐TiO2–x‐S) as an advanced anode for the Na ion battery. An amorphous shell (≈3 nm) is induced by the Ar/H2 plasma, which brings about the subsequent high S doping concentration (≈4.68 at%) and deep doping depth. Experimental results and density functional theory calculations demonstrate greatly facilitated ion diffusion, improved electronic conductivity, and an increased mobility rate of holes for R‐TiO2−x‐S, which result in superior rate capability (264.8 and 128.5 mAh g−1 at 50 and 10 000 mA g−1, respectively) and excellent cycling stability (almost 100% retention over 6500 cycles). Such improvements signify that plasma treatment offers an innovative and general approach toward designing advanced battery materials.
Surface amorphous TiO2 with a high content of cation‐site‐doped S is achieved with the assistance of plasma. Those features give rise to greatly improved intrinsic electronic conductivity and enhanced sodium‐ion diffusion of TiO2, leading to superior sodium‐storage performance. This strategy opens a new avenue to design advanced materials for energy‐storage systems.
Conjugated polymers with high thermoelectric performance enable the fabrication of low‐cost, large‐area, low‐toxicity, and highly flexible thermoelectric devices. However, compared to their p‐type ...counterparts, n‐type polymer thermoelectric materials show much lower performance, which is largely due to inefficient doping and a much lower conductivity. Herein, it is reported that the development of a donor–acceptor (D–A) polymer with enhanced n‐doping efficiency through donor engineering of the polymer backbone. Both a high n‐type electrical conductivity of 1.30 S cm−1 and an excellent power factor (PF) of 4.65 µW mK−2 are obtained, which are the highest reported values among D–A polymers. The results of multiple characterization techniques indicate that electron‐withdrawing modification of the donor units enhances the electron affinity of the polymer and changes the polymer packing orientation, leading to substantially improved miscibility and n‐doping efficiency. Unlike previous studies in which improving the polymer‐dopant miscibility typically resulted in lower mobilities, the strategy maintains the mobility of the polymer. All these factors lead to prominent enhancement of three orders magnitude in both the electrical conductivity and the PF compared to those of the non‐engineered polymer. The results demonstrate that proper donor engineering can enhance the n‐doping efficiency, electrical conductivity, and thermoelectric performance of D–A copolymers.
1000‐fold enhancements in n‐type electrical conductivity and power factor of a donor–acceptor copolymer are obtained by donor engineering. Donor engineering enhances electron affinity and n‐doping efficiency, prevents phase separation, lowers hopping barrier and keeps mobility unaffected. A record electrical conductivity of 1.30 S cm−1 and a power factor of 4.65 μW mK−2 are achieved in this work.
Developing cost‐effective and efficient electrocatalysts for oxygen evolution reaction (OER) is of paramount importance for the storage of renewable energies. Perovskite oxides serve as attractive ...candidates given their structural and compositional flexibility in addition to high intrinsic catalytic activity. In a departure from the conventional doping approach utilizing metal elements only, here it is shown that non‐metal element doping provides an another attractive avenue to optimize the structure stability and OER performance of perovskite oxides. This is exemplified by a novel tetragonal perovskite developed in this work, i.e., SrCo0.95P0.05O3–
δ
(SCP) which features higher electrical conductivity and larger amount of O2
2−/O− species relative to the non‐doped parent SrCoO3–
δ
(SC), and thus shows improved OER activity. Also, the performance of SCP compares favorably to that of well‐developed perovskite oxides reported. More importantly, an unusual activation process with enhanced activity during accelerated durability test (ADT) is observed for SCP, whereas SC delivers deactivation for the OER. Such an activation phenomenon for SCP may be primarily attributed to the in situ formation of active A‐site‐deficient structure on the surface and the increased electrochemical surface area during ADT. The concept presented here bolsters the prospect to develop a viable alternative to precious metal‐based catalysts.
Phosphorus‐doped perovskite oxide SrCo0.95P0.05O3–
δ
(SCP) is demonstrated for the first time as a high‐efficient oxygen evolution reaction (OER) electrocatalyst in alkaline solution. The SCP exhibits enhanced OER activity and stability compared to parent SrCoO3–
δ
(SC). More importantly, an activation process is observed for SCP during accelerated durability test, which primarily originates from the in situ formed Sr‐deficient layer on its surface.
Novel MnO
-doped holey carbon materials were obtained by an efficient and facile synthetic method using chitosan, potassium hydroxide and potassium permanganate as the raw materials. The carbon ...framework with high specific surface area was derived from chitosan by carbonization and activation approach, afterwards, MnO
nanorods were grown on the surface of porous carbon by one-step agitation method and the MnO
-doped holey carbon material was obtained. The scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, N
adsorption-desorption measurements, Raman spectroscopy and X-ray photoelectron spectroscopy were employed to analyze the physicochemical characteristics of the MnO
-doped holey carbon materials. The electrochemical performance of these materials displayed well through relative tests including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy measurements in 6.0 M KOH solution. Especially, this as-obtained electrode material with the optimum ratio presented a high gravimetric capacitance (460F g
at 0.2 A g
) and exceptional capacitance reservation (91.67% at 10 A g
over 10,000 cycles) in the three-electrode system with 6.0 M KOH solution as the electrolyte.
Carbon element is a widely distributed element in nature, and carbon nanomaterials have been widely used in the fields of energy storage, CO2 capture and H2 storage, high capacity adsorption of ...specific pollutants and sensors. In order to meet the more advanced applications of carbon nanomaterials, heteroatom doping of carbon materials has attracted much attention in recent years. Among the several usual elements for doping, sulfur atoms have many attractive characteristics, such as, large atomic radius, small electronegativity, many electrons and various covalent bonds. These characteristics make them play unique roles in different applications. Here, a comprehensive review is presented for establishing the connection between the basic properties and the performance, and revealing how sulfur doping has improved the applications. In-situ and post-treatment synthetic routes of S-doped carbons are summarized. Characteristics and properties of S-doped carbons including molecular structure, electronegativity, conductivity, hydrophilicity and co-doping effects are stated. And, the promising applications of S-doped carbons are presented. Especially, we put emphasis to explain the effects of S doping on the properties and application performances for S-doped carbons. At the end, a perspective is presented.
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•In-situ and post-treatment synthetic routes of S-doped carbons.•Molecular structure, electronegativity, conductivity and hydrophilicity of S-doped carbons.•Promising applications of S-doped carbons.
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