The homogeneous incorporation of heteroatoms into two-dimensional C nanostructures, which leads to an increased chemical reactivity and electrical conductivity as well as enhanced synergistic catalysis as a conductive matrix to disperse and encapsulate active nanocatalysts, is highly attractive and quite challenging. In this study, by using the natural and cheap hydrotropic amino acid proline—which has remarkably high solubility in water and a desirable N content of ~12.2 wt.%—as a C precursor pyrolyzed in the presence of a cubic KCl template, we developed a facile protocol for the large-scale production of N-doped C nanosheets with a hierarchically porous structure in a homogeneous dispersion. With concomitantly encapsulated and evenly spread Fe2O3 nanoparticles surrounded by two protective ultrathin layers of inner Fe3C and outer onion-like C, the resulting N-doped graphitic C nanosheet hybrids (Fe2O3@Fe3C-NGCNs) exhibited a very high Li-storage capacity and excellent rate capability with a reliable and prolonged cycle life. A reversible capacity as high as 857 mAh•g–1 at a current density of 100 mA•g–1 was observed even after 100 cycles. The capacity retention at a current density 10 times higher—1,000 mA•g–1—reached 680 mAh•g–1, which is 79% of that at 100 mA•g–1, indicating that the hybrids are promising as anodes for advanced Li-ion batteries. The results highlight the importance of the heteroatomic dopant modification of the NGCNs host with tailored electronic and crystalline structures for competitive Li-storage features.
Developing low-energy input route for conversion of methane (CH4) to value-added methanol (CH3OH) at room temperature is important in environment and industry. Bonding in electron donor-acceptor hybrid can potentially promote charge transfer and photocatalytic efficiency of CH4 conversion. Herein, bonding in electron donor rhodamine B (RhB)-acceptor (TiO2) hybrid (RhB/TiO2) significantly promotes the selectivity of photocatalytic oxidation of CH4 to CH3OH and utilization of visible light (low-energy photons) at ambient condition. Even under green light irradiation (λ = 550 nm), the noble-metal-free RhB/TiO2 hybrid synthesized presents enhanced oxidation of CH4 to CH3OH with a generation rate of 143 µmol·g−1·h−1 and selectivity of 94%. This work demonstrates the possibility and feasibility of noble-metal-free catalysts for activating CH4 under visible light at room temperature.
Elucidating the reaction mechanism of hydrazine oxidation reaction (HzOR) over carbon-based catalysts is highly propitious for the rational design of novel electrocatalysts for HzOR. In present work, isolated first-row transition metal atoms have been coordinated with N atoms on the graphite layers of carbon nanotubes via a M-N4-C configuration (MSA/CNT, M=Fe, Co and Ni). The HzOR over the three single atom catalysts follows a predominant 4-electron reaction pathway to emit N2 and a negligible 1-electron pathway to emit trace of NH3, while their electrocatalytic activity for HzOR is dominated by the absorption energy of N2H4 on them. Furthermore, FeSA/CNT reverses the passivation effect on Fe/C and shows superior performance than CoSA/CNT and NiSA/CNT with a recorded high mass activity for HzOR due to the higher electronic charge of Fe over Co and Ni in the M-N4-C configuration and the lowest absorption energy of N2H4 on FeSA/CNT among the three MSA/CNT catalysts.
In order to well arrange active sites and avoid byproducts, the reasonable structured carrier nanocatalyst plays a crucial role in high catalytic performance, but still remains a challenge. Herein, the layered CuNi-Cu2O/NiAlOx nanosheets have been constructed through hydrothermal synthesis followed by calcination and H2 reduction treatment process. The in-situ formed CuNi nanoalloys (NAs) and nano-Cu2O were evenly distributed on the bilateral surface of layered NiAlOx nanosheets. Based on the planar structure of nanosheet, the synergy between catalytic active CuNi NAs and photocatalytic active nano-Cu2O endows CuNi-Cu2O/NiAlOx nanosheets with rapid conversion efficiency for catalyzing p-nitrophenol (p-NP, 14 mg·L−1) to p-aminophenol (p-AP) in 32 s with the reaction rate constant k up to 0.1779 s−1, and no obvious performance decay can be observed even over 27 cycles. Moreover, high concentration of p-NP at 10 and 20 g·L−1 could be reduced to p-AP within 14 and 20 min, respectively. Such designed nanoalloy/bimetal-oxide heterostructure can provide a solution for rapid conversion of aminoaromatics from nitroaromatics wastewater even at a large concentration range.
One dimensional (1D) nanostructures attract considerable attention, enabling a broad application owing to their unique properties. However, the precise mechanism of 1D morphology attainment remains a matter of debate. In this study, ultrafast picosecond (ps) laser-induced treatment on upconversion nanoparticles (UCNPs) is offered as a tool for 1D-nanostructures formation. Fragmentation, reshaping through recrystallization process and bioadaptation of initially hydrophobic (β-Na1.5Y1.5F6: Yb3+, Tm3+/β-Na1.5Y1.5F6) core/shell nanoparticles by means of one-step laser treatment in water are demonstrated. “True” 1D nanostructures through “Medusa”-like structures can be obtained, maintaining anti-Stokes luminescence functionalities. A matter of the one-dimensional UCNPs based on direction of energy migration processes is debated. The proposed laser treatment approach is suitable for fast UCNP surface modification and nano-to-nano transformation, that open unique opportunities to expand UCNP applications in industry and biomedicine.
Enhancing electrocatalytic water splitting performance by modulating the intrinsic electronic structure is of great importance. Here, porous bimetallic oxide and chalcogenide nanosheets grown on carbon paper denoted as NiCo2X4/CP (X = O, S, and Se) are prepared to demonstrate how the anion components affect the electronic structures and thereby disclose the correlation between their intermediates interaction and catalytic activities. The experimental characterization and theoretical calculation demonstrate that Se and S substitution can promote the ratio of Co3+/Co2+ and thereby modulate the electronic structure accompanied with the upshift of d band centers, which not only enhance the inner conductivity but also regulate the interaction between the catalyst surface and intermediates, especially for the adsorption of absorbed H and hydroperoxy intermediates towards respective hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As a result, a full alkaline electrolyzer using NiCo2Se4/CP and NiCo2S4/CP as cathode and anode delivers a low voltage of 1.51 V at 10 mA·cm−2, which is comparable even superior to most transition metal-based electrolyzers.
Designing earth-abundant electrocatalysts with high performance towards water oxidation is highly decisive for the sustainable energy technologies. This study develops a facile natural corrosion approach to fabricate nickel-iron hydroxides for water oxidation. The resulted electrode demonstrates an outstanding activity and stability with an overpotential of 275 mV to deliver 10 mA·cm−2. Experimental and theoretical results suggest the corrosion-induced formation of hydroxides and their transformation to oxyhydroxides would account for this excellent performance. This work not only provides an interesting corrosion approach for the fabrication of excellent water oxidation electrode, but also bridges traditional corrosion engineering and novel materials fabrication, which would offer some insights in the innovative principles for nanomaterials and energy technologies.
The metal—organic frameworks (MOFs) are expected as ideal biomimetic enzymes for colorimetric glucose detection because of their large surface areas, well defined pore structures, tunable chemical composition, and multi-functional sites. However, the intrinsically chemical instability and low mimetic enzyme activity of MOFs hinder the application of them in imitating the enzyme reactions. In this work, we demonstrated a metal-MOF synergistic catalysis strategy, by loading Pt nanoparticles (Pt NPs) on MIL-88B-NH2 (Fe-MOF) to increase peroxidase-like activity for the detection of glucose. The induced electrons transfer from Pt atom to Fe atom accelerated the redox cycling of Fe3+/Fe2+, improved the overall efficiency of the peroxidase-like reaction, and enabled the efficient and robust colorimetric glucose detection, which was proved by both experiments and density functional theory (DFT) calculation. Additionally, the sensitivity and chemical stability of this synergistic effect strategy to detect the glucose are not affected by the complex external factors, which represented a great potential in fast, easy, sensitive, and specific recognition of clinical diabetes.
The rational fabrication of highly efficient electrocatalysts with low cost toward oxygen evolution reaction (OER) is greatly desired but remains a formidable challenge. In this work, we present a facile and straightforward method of incorporating NiCo-layered double hydroxide (NiCo-LDH) into GO-dispersed CNTs (GO-CNTs) with interconnected configuration. X-ray absorption spectroscopy (XAS) reveals the strong electron interaction between NiCo-LDH and the underlying GO-CNTs substrate, which is supposed to facilitate charge transfer and accelerate the kinetics for OER. By tuning the amount of CNTs, the optimized NiCo-LDH/GO-CNTs composite can achieve a low overpotential of 290 mV at 10 mA·cm−2 current density, a small Tafel slope of 66.8 mV·dec−1 and robust stability, superior to the pure NiCo-LDH and commercial RuO2 in alkaline media. The preeminent oxygen evolution performance is attributed to the synergistic effect stemming from the merits and the intimate electron interaction between LDH and GO-CNTs. This allows NiCo-LDH/GO-CNTs to be potentially applied in an industrial non-noble metal-based water electrolyzer as the anodic catalysts.
Emerging layered semiconductors present multiple advantages for optoelectronic technologies including high carrier mobilities, strong light-matter interactions, and tunable optical absorption and emission. Here, metal-semiconductor-metal avalanche photodiodes (APDs) are fabricated from Bi2O2Se crystals, which consist of electrostatically bound [Bi2O2]2+ and [Se]2− layers. The resulting APDs possess an intrinsic carrier multiplication factor up to 400 at 7 K with a responsivity gain exceeding 3,000 A/W and bandwidth of ~ 400 kHz at a visible wavelength of 515.6 nm, ultimately resulting in a gain bandwidth product exceeding 1 GHz. Due to exceptionally low dark currents, Bi2O2Se APDs also yield high detectivities up to 4.6 × 1014 Jones. A systematic analysis of the photocurrent temperature and bias dependence reveals that the carrier multiplication process in Bi2O2Se APDs is consistent with a reverse biased Schottky diode model with a barrier height of ~ 44 meV, in contrast to the charge trapping extrinsic gain mechanism that dominates most layered semiconductor phototransistors. In this manner, layered Bi2O2Se APDs provide a unique platform that can be exploited in a diverse range of high-performance photodetector applications.