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.
Heteroatom doping in carbon‐based anode materials is crucial to improve their capacity and promoting the practical application of low‐cost potassium‐ion batteries (KIBs). Herein, ...the selenium/nitrogen co‐doped amorphous carbon nanocluster (SeN‐ACN) anodes exhibit an ultra‐high reversible capacity of 621 mAh g−1 at 0.75 C (225 mA g−1) and a capacity retention of 93% after 2000 cycles at 5 C, which represent a remarkable achievement in potassium storage in nonmetallic doped carbon materials. This is attributed to the synergistic effects of Se/N co‐doping and their anchoring effects on potassium ions. As a proof of concept, a potassium‐based dual‐ion battery (K‐DIB), which consists of a SeN‐ACN anode and low‐cost graphite cathode, demonstrates a high reversible capacity of 118 mAh g−1 at 150 mA g−1 with a high cut‐off voltage of 5.2 V. Moreover, it presents excellent long‐term cycling performance, with 70% capacity retention after 500 cycles, among the best reported results of K‐DIBs.
Thanks to the synergistic and anchoring effect of Se/N co‐doping in amorphous carbon nanoclusters, the SeN‐ACNs‐based KIB half‐cells demonstrate high capacity of 621 mAh g–1 at 0.75 C with high‐capacity retention of 93% after 2000 cycles at 5 C. Furthermore, the integration of SeN‐ACNs/EG K‐DIBs also exhibits a high capacity of 118 mAh g–1 and remarkable cycling performance.
As a representative composite metal oxide belonging to a perovskite, strontium titanate (SrTiO
3
) possesses the merits of chemical stability, low toxicity and low cost, endowing it with significant ...application potentials in environmental remediation, clean energy generation and valuable chemical production from greenhouse gas conversion. However, the pure-phase SrTiO
3
suffers from many fatal weaknesses, especially the wide energy bandgap and low photoexcited electron–hole pair separation efficiency, thus limiting its photocatalytic performance and large-scale applications. To address this issue, researchers have made great efforts to modify the electronic and physicochemical structure of SrTiO
3
. In particular, doping treatments have attracted considerable attention, but some problems still block effective doping, while impropriate doping might worsen the photocatalytic performance of SrTiO
3
by introducing the photogenerated hole–electron pair recombination centres. Consequently, many challenges remain for this research topic that is undergoing an intense study. This short review presents the hot spots of appropriate doping treatments of SrTiO
3
for photocatalytic performance enhancement over recent years. Different kinds of doping species are systematically discussed. The current problems that remain are summarized and analysed, and the perspectives for the rational doping of SrTiO
3
are presented.
Graphical abstract
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.
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.
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.
PDF
