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.
Large‐area “in situ” transition‐metal substitution doping for chemical‐vapor‐deposited semiconducting transition‐metal‐dichalcogenide monolayers deposited on dielectric substrates is demonstrated. In ...this approach, the transition‐metal substitution is stable and preserves the monolayer's semiconducting nature, along with other attractive characteristics, including direct‐bandgap photoluminescence.
This work demonstrates that photochemical doping of CVD‐grown graphene can be easily achieved using photoacid (PAG) and photobase (PBG) generators such as triphenylsulfonium ...perfluoro‐1‐butanesufonate (TPS‐Nf) and 2‐nitrobenzyl N‐cyclohexylcarbamate (NBC). The TPS‐Nf ionic onium salt photoacid generator does not noticeably dope or alter the electrical properties of graphene when coated onto the graphene surface, but is very effective at inducing p‐doping of graphene upon exposure of the PAG‐coated graphene sample. Likewise, the neutral NBC photobase generator does not significantly affect the electrical properties of graphene when coated, but upon exposure to ultraviolet light produces a free amine, which induces n‐doping of the graphene. Electrical measurements show that the doping concentration can be modulated by controlling the deep ultraviolet (DUV) light exposure dose delivered to the sample. The interaction between both dopants and graphene is also investigated. The photochemical doping process is able to tune the work function of the single‐layer graphene samples used in this work from 3.4 eV to 5.3 eV. Finally, a p–n junction is fabricated and analyzed, showing that it is possible to control the position of the two current minima (two Dirac points) in the ambipolar p–n junction.
Photochemical p‐ and n‐doping of CVD‐grown graphene is achieved using photoacid and photobase generators which do not themselves affect the electrical properties of the graphene, but which prime it for doping upon exposure to UV light. The doping level can be modulated by adjusting the exposure dose. This process tunes the Fermi level of the graphene sample.
The use of lead-free piezoelectric materials in high-power applications requires a high mechanical quality factor Qm and temperature-stable ferroelectric properties. In this article, the influence of ...Mg-doping on the 0.94Na1/2Bi1/2TiO3-0.06BaTiO3 system is analysed with focus on the role of defects related to ferroelectric hardening. Temperature stability (depolarization temperature), electromechanical properties (piezoelectric activity, Qm), electrical properties (conductivity) and crystal structure for compositions were quantified. Compositions with similar amount of Zn-doping were analyzed for reference. A drastic increase in electrical conductivity at −0.3/−0.5 mol% Mg was associated with a concomitant increase in Qm. Similar behavior in Zn-doped compositions provides a basis for a more comprehensive mechanistic understanding of acceptor doping in these lead-free piezoceramics. The very high and almost vibration-velocity-independent Qm above 800 makes Mg-doped 0.94Na1/2Bi1/2TiO3-0.06BaTiO3 an excellent candidate for high-power application.
Hierarchical nanostructured architectures are demonstrated as an effective approach to develop highly active and bifunctional electrocatalysts, which are urgently required for efficient rechargeable ...metal–air batteries. Herein, a mesoporous hierarchical flake arrays (FAs) structure grown on flexible carbon cloth, integrated with the microsized nitrogen‐doped carbon (N‐doped C) FAs, nanoscaled P‐doped CoSe2 hollow clusters and atomic‐level P‐doping (P‐CoSe2/N‐C FAs) is described. The P‐CoSe2/N‐C FAs thus developed exhibit a reduced overpotential (≈230 mV at 10 mA cm−2) toward oxygen evolution reaction (OER) and large half‐wave potential (0.87 V) for oxygen reduction reactions. The excellent bifunctional electrocatalytic performance is ascribed to the synergy among the hierarchical flake arrays controlled at both micro‐ and nanoscales, and atomic‐level P‐doping. Density functional theory calculations confirm that the free energy for the potential‐limiting step is reduced by P‐doping for OER. An all‐solid‐state zinc–air battery made of the P‐CoSe2/N‐C FAs as the air‐cathode presents excellent cycling stability and mechanical flexibility, demonstrating the great potential of the hierarchical P‐CoSe2/N‐C FAs for advanced bifunctional electrocatalysis.
Multilevel N‐doped carbon flake arrays embedded with P‐doped CoSe2 hollow nanoclusters exhibit excellent bifunctional electrocatalytic performance toward both oxygen evolution and oxygen reduction reactions, which are ascribed to the synergy among the hierarchical nanoarrays structure controlled at both micro‐ and nanoscales, and atomic level P‐doping.
It is demonstrated that the n‐type thermoelectric performance of donor–acceptor (D–A) copolymers can be enhanced by a factor of >1000 by tailoring the density of states (DOS). The DOS distribution is ...tailored by embedding sp2‐nitrogen atoms into the donor moiety of the D–A backbone. Consequently, an electrical conductivity of 1.8 S cm−1 and a power factor of 4.5 µW m−1 K−2 are achieved. Interestingly, an unusual sign switching (from negative to positive) of the Seebeck coefficient of the unmodified D–A copolymer at moderately high dopant loading is observed. A direct measurement of the DOS shows that the DOS distributions become less broad upon modifying the backbone in both pristine and doped states. Additionally, doping‐induced charge transfer complexes (CTC) states, which are energetically located below the neutral band, are observed in DOS of the doped unmodified D–A copolymer. It is proposed that charge transport through these CTC states is responsible for the positive Seebeck coefficients in this n‐doped system. This is supported by numerical simulation and temperature dependence of Seebeck coefficient. The work provides a unique insight into the fundamental understanding of molecular doping and sheds light on designing efficient n‐type OTE materials from a perspective of tailoring the DOS.
Significantly boosted n‐type organic thermoelectric performance of donor–acceptor (D–A) copolymers by a factor of three orders of magnitude is realized by tailoring the density of states through molecular design. This strategy improves the electrical conductivity effectively and reduces the loss of the Seebeck coefficient, leading to a very good power factor of 4.5 µW m−1 K−2 for doped D–A copolymers.
Organic crystals are generally brittle and tend to crack under applied stress. Doped organic crystals are even more brittle because of lattice defects. Herein, the first doped organic crystals 1d@2d, ...which display elastic bending ability under applied stress, are reported. Moreover, the potential applications of elastic‐doped crystals 1d@2d in flexible optoelectronics are impressively demonstrated. The elastic crystals 1d@2d with high quality and large size are crystalized by a simple and unique “self‐doping” process, which is a regular solution evaporation of crude product 1d (2,5‐dihydro‐3,6‐bis(octylamino)terephthalate) containing a minute amount of 2d (3,6‐bis(octylamino)terephthalate) as the oxidized byproduct. The host 1d is easily crystallized to form elastic crystals but is nonfluorescent, while the guest 2d has poor crystallinity and is highly emissive. The doping approach integrates the advantages of both 1d and 2d, and thus endows doped crystals 1d@2d with good elasticity as well as intense orange fluorescence. Taking these advantages, the application potentials of these doped crystals 1d@2d are evaluated by measuring optical waveguide and amplified spontaneous emission in both the straight and bent states.
Elastic‐doped organic crystals 1d@2d are crystalized by a simple and unique “self‐doping” process. Taking advantage of the good elasticity and intense fluorescence, a flexible optical waveguide and amplified spontaneous emission are realized in bent crystals 1d@2d, highlighting the feature of elasticity and the potential applications in flexible optoelectronics.
PDF
