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Highly monodisperse colloidal InAs quantum dots (QDs) with superior optoelectronic properties are promising candidates for various applications, including infrared photodetectors and photovoltaics. Recently, a synthetic process involving continuous injection has been introduced to synthesize uniformly sized InAs QDs. Still, synthetic efforts to increase the particle size of over 5 nm often suffer from growth suppression. Secondary nucleation or interparticle ripening during the growth accompanies the inhomogeneity in size as well. In this study, we propose a growth model for the continuous synthetic processing of colloidal InAs QDs based on molecular diffusion. The experimentally validated model demonstrates how precursor solution injection reduces monomer flux, limiting particle growth during synthesis. As predicted by our model, we control the diffusion dynamics by tuning reaction volume, precursor concentration, and injection rate of precursor. Through diffusion-dynamics-control in the continuous process, we synthesize the InAs QDs with a size over 9.0-nm (1Smax of 1600 nm) with a narrow size distribution (12.2%). Diffusion-dynamics-controlled synthesis presented in this study effectively manages the monomer flux and thus overcome monomer-reactivity-originating size limit of nanocrystal growth in solution., Monodisperse colloidal InAs quantum dots have been envisioned as Pb-free materials for various infrared applications. Here, the authors provide a growth model based on monomer diffusion dynamics, enabling extended spectral coverage of InAs quantum dots beyond 1Smax of 1600 nm.

We prepared a highly active and stable cathode catalyst for a solid oxide electrolysis cell (SOEC), decorated with in situ exsolved Fe nanoparticles (NPs) socketed on La1.2Sr0.8Mn0.4Fe0.6O4−α (R.P.LSMF), toward the CO2 electrolysis reaction to produce CO selectively. This catalyst was derived from the perovskite structure of La0.6Sr0.4Mn0.2Fe0.8O3−δ (LSMF) by simple annealing in a H2 atmosphere and showed high current densities of 2.04, 1.43, and 0.884 A cm−2 at 850, 800, and 750 °C, respectively, at a voltage of 1.5 V with corresponding total polarization resistance values of 0.205, 0.326, and 0.587 Ω cm2, respectively, at an open circuit voltage. The highly improved performance should be ascribed to the in situ exsolved Fe NPs anchored on Ruddlesden–Popper oxide and to the increased contents of oxygen vacancies in R.P.LSMF. More importantly, this active catalyst also exhibited a stable voltage profile for 100 h operation at an constant current density of 1.8 A cm−2, suggesting that the catalyst Fe–R.P.LSMF proposed in this study is a highly promising candidate for use in an efficient SOEC cathode for CO2 electrolysis processes.

The yield and length of carbon nanotube (CNT) forests were increased by using regenerated quartz tubes. Carbonaceous impurities remained in the walls of the regenerated quartz tube. When CNT forests were synthesized in regenerated quartz tubes, the carbonaceous impurities were released at temperatures between 400 and 450 °C, and by facilitating nucleation, caused increase in the number density (NCat) of Fe catalyst particles on the substrate. The substrate in the regenerated quartz tube had NCat = 6.0 × 1010/cm2, whereas a fresh quartz tube had NCat = 7.7 × 109/cm2. Furthermore, after the early stage (5 s) of synthesis process, the volumetric density of the CNT forest was higher in the regenerated quartz tube (0.016 g/cm3) than in the fresh quartz tube (0.011 g/cm3). When a regenerated quartz plate was placed in a fresh quartz tube, CNT forests were longer than when a fresh quartz tube was used alone. These results suggest that the carbonaceous impurity in the quartz tube establishes an environment that increases the reproducibility of synthesis of long CNT forests.

We report a highly improved cathode catalyst by doping fluorine anions in oxygen sites of Ruddlesden-Popper material for CO2 electrolysis to produce CO in solid oxide electrolysis cells (SOECs). Th...

Herein, we demonstrate the ultraviolet (UV) light activated high-performance room-temperature NO gas sensor based on nitrogen-doped graphene quantum dots (NGQDs)-decorated TiO2 hybrid structure. Ti...

The application of electrocatalysts with high activity to a practical water electrolysis cell is a crucial challenge for the production of pure hydrogen and commercialization of the water electrolyzer. Herein, a nanosized Cu0.5Co2.5O4 catalyst synthesized by co-precipitation by adjusting pH is applied to the anion exchange membrane water electrolysis (AEMWE) cell as an anode, which is demonstrated to have higher efficiency and stability than noble metal-based anodes. The composition (Cu/Co) and morphology of Cu0.5Co2.5O4 change as the pH increases and then nanoparticles are formed at pH 11, where oxygen vacancies are formed by the etching of Cu. In the density functional theory study, the electronic structure of Co modified by Cu in the Co3O4 lattice leads to an optimal adsorption strength, resulting in a free energy diagram in which the potential of Cu0.5Co2.5O4 (1.756 V vs. reversible hydrogen electrode, RHE) is more thermodynamically favorable than that of Co3O4 (1.951 V vs. RHE). The Cu0.5Co2.5O4 catalyst has a recorded overpotential of 285 mV at 10 mA cm−2 in 1 M KOH. Furthermore, the AEMWE cell using Cu0.5Co2.5O4 as an anode exhibited a current density of 1.3 A cm−2 at 1.8 V, which is the highest performance among the reported papers and maintains around 80% energy conversion efficiency for 100 hours.

The selective and efficient electrocatalytic transformation of carbon dioxide (CO2) to multicarbon alcohols (e.g., C2H5OH and C3H7OH) is a challenge in renewable and sustainable energy research. Herein, a series of hybrid catalysts consisting of Cu nanoparticles supported on N-doped porous carbon (Cu/NPC) were prepared. It was demonstrated that the selectivity for C2H5OH or C3H7OH could be tuned by introducing N-doped porous carbon materials as cocatalysts with different pyridinic N contents, which could in situ produce a reactive CO intermediate from CO2. By varying the pyridinic N content, highly selective production of multicarbon alcohols was achieved using the Cu/NPC hybrid catalysts with a high faradaic efficiency for one pot production of multicarbon alcohols up to 73.3% at −1.05 V (vs. RHE). The faradaic efficiency for C2H5OH and C3H7OH was 64.6% and 8.7%, respectively. The pyridinic N species were likely the CO-producing sites and together with Cu catalytic sites acted cooperatively to produce C2H5OH and C3H7OH via a two-site mechanism for efficient CO2 reduction to multicarbon alcohols. These findings provide novel guidance for the rational design of electrocatalysts and for tuning the catalytic activity and selectivity for multicarbon alcohol production from CO2.

We developed a new and efficient sulfur-tolerant catalyst for application as a solid oxide electrolysis cell (SOEC) cathode designed with in situ exsolved CoNi alloy nanoparticles anchored on a Ruddlesden–Popper (R.P.) support of La1.2Sr0.8Co0.4Mn0.6O4 and evaluated its catalytic activity for CO2 electrolysis to CO under a CO2 gas stream containing H2S species. This catalyst was prepared by in situ annealing of a perovskite derivative (La0.6Sr0.4Co0.5Ni0.2Mn0.3O3) in a 20% H2/N2 gas at 800 °C. The catalyst exhibited good reversibility of structural transitions during reduction and re-oxidation processes. A high current density of 703 mA cm−2 was achieved at 1.3 V and 850 °C with a maximum faradaic efficiency of 97.8%. In situ grown CoNi alloy nanoparticles and the high oxygen vacancy content in the R.P. support were responsible for its high catalytic activity and efficiency. Importantly, no sign of performance degradation was observed in galvanostatic tests over a period of 90 h operation under H2S-containing CO2 gas conditions. Moreover, the catalyst showed no noticeable structural changes even after exposure to 100 ppm H2S/N2, indicating that the catalyst developed in this study is highly active for CO2 electrolysis with a high tolerance against sulfur-poisoning species. Therefore, this Ruddlesden–Popper material with in situ exsolved CoNi alloy nanoparticles should be a promising cathode catalyst for practical application to H2S-containing CO2 gas streams that are effluents of power stations or steel making plants.

Converting CO2 into useful chemicals through an electrocatalytic process is an attractive solution to reduce CO2 in the atmosphere. However, the process suffers from high overpotential, low activity, or poor product selectivity. In this study, N,S dual-doped carbon nanoweb (NSCNW) materials were proposed as an efficient nonmetallic electrocatalyst for CO2 reduction. The NSCNW catalysts preferentially and rapidly converted CO2 into CO with a high Faradaic efficiency of 93.4 % and a partial current density of -5.93 mA cm-2 at a low overpotential of 490 mV. A small Tafel slope value (93 mV dec-1 ) was obtained, demonstrating a high rate for CO2 reduction. Moreover, the catalysts also exhibited a quite stable current-density profile during 20 h with a high CO Faradaic efficiency above 90 % throughout the electrolysis reaction. The high catalytic performance of the catalysts for CO2 reduction could be attributed to synergistic effects associated with the structural advantages of 3 D carbon nanoweb structures and effective S doping of the carbon materials with the highest ratio of thiophene-like S to oxidized S species.

We report a highly active Ruddlesden-Popper material with a mechanism of in situ exsolution of Co nanoparticles and its use as an effective catalyst for CO2 reduction to produce CO in a solid oxide electrolysis cell. This catalyst is simply prepared by transforming a perovskite of La0.6Sr0.4Co0.7Mn0.3O3 and revealed a good reversibility of structural transition between the Ruddlesden-Popper and the perovskite structure during reaction cycles. A very high current density of 630 mA/cm2 can be accomplished at a voltage of 1.3 V and temperature of 850 °C with a very high Faraday efficiency of 95% or larger. More importantly, no sign of degradation is indicated as observed by galvanostatic stability test, implying that this Ruddlesden-Popper structure is highly robust as the cathode catalyst for the CO2 electrolysis. In situ exsolved Co nanoparticles and high concentration of oxygen vacancies caused by the structural transition are responsible for its high stability and catalytic activity, as characterized by several physicochemical analyses.

A Cu–Co–P electrocatalyst for hydrogen evolution reaction (HER) was designed with a dendritic and porous foam structure. Fabricated by one-step electrodeposition with binary alloy on a hydrogen bub...

Flexible materials with sufficient mechanical endurance under bending or folding is essential for flexible electronic devices. Conventional rigid materials such as metals and ceramics are mostly brittle so that their properties can deteriorate under a certain amount of strain. In order to utilize high-performance, but brittle conventional materials in flexible electronics, we propose a novel flexible substrate structure with a low-modulus interlayer. The low-modulus interlayer reduces the surface strain, where active electronic components are placed. The bending results with indium tin oxide (ITO) show that a critical bending radius, where the conductivity starts to deteriorate, can be reduced by more than 80% by utilizing the low-modulus layer. We demonstrate that even rigid electrodes can be used in flexible devices by manipulating the structure of flexible substrate.

Converting CO2 into valuable chemicals using electrocatalysis is an attractive approach for sustainable energy storage and artificial carbon cycle. In this study, atomically dispersed Ir species (Ad-Ir) that are supported on three-dimensional (3D) porous carbon networks are proposed as electrocatalysts for highly efficient CO2 conversion. The resulting catalysts can preferentially and rapidly produce CO with a high Faradaic efficiency of 95.6 % and a very high turnover frequency (TOF) value of 33,365 h−1. Furthermore, it shows no obvious decay in both FE for CO and current density over 20 h of continuous operation. Based on detailed experimental studies and density functional theory (DFT) calculations, such outstanding catalytic performance for CO2 conversion to CO production can be attributed to the structural advantages of 3D network of porous carbon and atomically dispersed Ir species on the 3D carbon support.

In this study, a highly efficient Pd catalyst supported on a conducting polymer-carbon composite was prepared for electro-oxidations of ethanol and formic acid. A polypyrrole-carbon composite was synthesized and modified by doping camphor sulfonic acid (CSA) during the polymerization step of pyrrole at room temperature. The resulting CSA-doped polypyrrole-carbon composite (PPyCC) showed significantly increased specific surface area and enhanced electrical conductivity compared with a polypyrrole-carbon composite without doping (PPyC). From the electrochemical tests, it was observed that the Pd-supported on CSA-doped polypyrrole-carbon composite (Pd/PPyCC) exhibited much larger electrochemical surface area (ECSA), enhanced catalytic activity and high durability towards the oxidations of ethanol and formic acid. The results indicate that the camphor sulfonic acid serving as both dopant and surfactant could improve the electrical conductivity and morphology of support material with enhanced interaction between Pd nanoparticles and support material.

The ladder-like polysilsesquioxanes containing both the bio-mimicking adhesive polycatechol and polyethylene oxide (CA-PEO-LPSQ) were synthesized as an organic-inorganic hybrid material and applied as a surface modifier for the preparation of a compatible polyethylene (PE) separator in high performing lithium ion batteries (LIBs). The dip-coating of CA-PEO-LPSQ onto PE (PE-M) separator was optimized at different alkaline pH values. The PE-M separator contained an inorganic ladder-like polysilsesquioxane-based backbone chain with organic moieties PEO and catechol acting as functional groups for enhancing the surface wettability, lithium ion conductivity, and thermal and electrochemical stability. The LIBs fabricated using PE-M as the separator, LiCoO2 as the cathode, and Li metal foil as the anode showed excellent capacity retention of 96% and 82% after the first cycle and 300th cycle at 0.5C rate, respectively, when compared to bare a PE separator exhibiting 95% and 15%, respectively.

The design of the cost-effective, efficient, and durable electrocatalysts for hydrogen evolution reaction (HER) is of great importance in the field of clean and renewable energies. In this study, Ni/NiO nanocomposite supported on N-doped carbon nanoweb (Ni/NiO/NCW) hybrid materials are proposed as an efficient electrocatalyst for HER in alkaline media. A series of Ni/NiO/NCW hybrid catalysts were prepared via polymerization of polypyrrole (PPy) in the presence of a surfactant, followed by incipient wetness impregnation and heat treatment techniques. The resulting Ni/NiO/NCW hybrid catalysts exhibit an excellent electrocatalytic properties with a lower overpotential of 105.3 mV (vs RHE) at 10 mA cm−2, a smaller value of Tafel slope (55.2 mV dec−1) and almost 100% Faradaic efficiency. It also shows good stability in performance attenuation during continuous cyclic voltammetry sweeps for 1000 cycles. Its excellent electrocatalytic performance for alkaline hydrogen evolution reaction can be attributed to the synergistic effect associated with the morphological benefit of 3D N-doped carbon nanoweb and Ni/NiO heterostructure with the optimal ratio of Ni to NiO.

A highly stable electrode material of Ruddlesden–Popper structure, La1.2Sr0.8Mn0.4Fe0.6O4 (RPLSMF), is prepared from La0.6Sr0.4Mn0.2Fe0.8O3 (LSMF) perovskite by in situ annealing in flowing H2 at the operation temperature of solid oxide fuel cells. The crystallinity, morphology, and oxidation states of each element and electrochemical properties of RPLSMF are characterized. Doping Mn into the B-site of RPLSMF improves the phase stability of the structure in H2 to prevent formation of La2O3. The XPS results also suggest that improved phase stability promotes formation of Fe2+/3+ pairs that facilitate fuel oxidation by redox coupling. Additionally, during phase transition to RPLSMF, metallic Fe nanoparticles form, which enlarge H2 chemisorption and oxidation sites. Consequently, RPLSMF exhibits outstanding and stable electrochemical activity with a maximum power density of 0.72 W cm−2 at 1073 K when used as an anode material in LSGM electrolyte-supported cells. As the phase transition between the RPLSMF and LSMF is reversible under a redox environment, RPLSMF/GDC is applied as an electrode in the symmetrical cell of RPLSMF-GDC/LSGM/LSMF-GDC. It exhibits a substantial power density of 0.64 W cm−2 with a total polarization resistance of 0.51 Ω cm2.

A replacement technique has been regarded as a promising strategy for both CH4 exploitation from gas hydrates and CO2 sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI hydrates due to their prevalence in natural gas hydrates. However, sII hydrates in nature have been also discovered in some regions, and the replacement mechanism in sII hydrates significantly differs from that in sI hydrates. In this study, we have intensively investigated the replacement reaction of sII (C3H8 + CH4) hydrate by externally injecting CO2/N2 (50:50) gas mixture with a primary focus on powder X-ray diffraction, Raman spectroscopy, NMR spectroscopy, and gas chromatography analyses. In particular, it was firstly confirmed that there was no structural transformation during the replacement of C3H8 + CH4 hydrate with CO2/N2 gas injection, indicating that sII hydrate decomposition followed by sI hydrate formation did not occur. Furthermore, the cage-specific replacement pattern of the C3H8 + CH4 hydrate revealed that CH4 replacement with N2 in the small cages of sII was more significant than C3H8 replacement with CO2 in the large cages of sII. The total extent of the replacement for the C3H8 + CH4 hydrate was cross-checked by NMR and GC analyses and found to be approximately 54%. Compared to the replacement for CH4 hydrate with CO2/N2 gas, the lower extent of the replacement for the C3H8 + CH4 hydrate with CO2/N2 gas was attributable to the persistent presence of C3H8 in the large cages and the lower content of N2 in the feed gas. The structural sustainability and cage-specific replacement observed in the C3H8 + CH4 hydrate with external CO2/N2 gas will have significant implications for suggesting target gas hydrate reservoirs and understanding the precise nature of guest exchange in gas hydrates for both safe natural gas production and long-term CO2 sequestration.

Recently, oxygen vacancy engineering represents a new direction for rational design of high-performance catalysts for electrochemical CO2 reduction (CO2RR). In this work, a series of amorphous MnOx catalysts with different concentrations of oxygen vacancies, namely, low (a-MnOx-L), pristine (a-MnOx-P), and high oxygen vacancy (a-MnOx-H), have been prepared by simple plasma treatments. The resultant a-MnOx-H catalyst with a larger amount of oxygen vacancy on the catalyst surface is able to preferentially convert CO2 to CO with a high Faradaic efficiency of 94.8% and a partial current density of 10.4 mA cm−2 even at a relatively lower overpotential of 510 mV. On the basis of detailed experimental results and theoretical density functional theory (DFT) calculations, the enhancement of CO production is attributable to the abundant oxygen vacancies formed in the amorphous MnOx which should favor CO2 adsorption/activation and promote charge transfer with the catalyst for efficient CO2 reduction.

Coke-resistant Ni catalyst supports are evaluated for steam reforming (SR) n-dodecane, the alkane used as a surrogate for diesel fuel in this study. Reactions are conducted at 800 °C for 5 h, with a molar steam-to-carbon ratio of 3.0 and a gas hourly space velocity of 20000 h−1. Thermally stable, coke-resistant supports loaded with 15 wt% Ni are prepared using the following potassium oxides: K2Ti2O5 (KTI), K4Zr5O12 (KZR), KNbO3 (KNB), KTaO3 (KTA), and K2WO4 (KW). Ni/KZR and Ni/KW show the best catalytic performance in the SR reaction due to their moderate-to-strong acidities and lack of porosity, which are necessary features for hydrocarbon cracking. Unfortunately, these catalysts are poorly stable under the defined operating conditions. KNB is the most suitable support due to its excellent thermal stability and coke-resistance; however, it lacks acidity. The acidity of KNB is enhanced by impregnation with ZrO2, which transforms it into an acidic oxide (ZR-KNB). ZR-KNB features high thermal stability and high coke-resistance during the SR of n-dodecane under the applied test conditions. The Ni/ZR-KNB catalyst delivers excellent SR performance with respect to both n-dodecane conversion and hydrogen selectivity.

Metal-free catalysts have gained substantial attention as a promising candidate to replace the expensive platinum (Pt) catalysts for the oxygen reduction reaction (ORR) which is a key process in low temperature fuel cells. Development of highly efficient and mass-producible N-doped carbon catalysts, however, remains to be a great challenge. In this study, N-doped porous carbon (NPC) materials were synthesized via a simple, cost-effective and scalable method for mass production by using the D-gluconic acid sodium salt, pyrrole, Triton X-100 and KOH. The resulting NPC possessed a multidirectional porous carbon network (SBET: 1026.6 m2 g−1, Vt: 1.046 cm3 g−1) with hierarchical porosity and plenty of graphitic N species (49.1%). Electrochemical tests showed that the NPC itself was highly active for the ORR under alkaline and acidic conditions via a four electron pathway for the complete reduction of O2 in water. More importantly, this NPC catalyst demonstrated better performance than commercial Pt/C catalysts in terms of long-term durability and methanol tolerance under both conditions.

A facile synthesis of nickel cobalt sulfide (NCS) nanoflowers have been deposited successfully onto binder free 3D nickel foam electrodes using simple successive ionic layer adsorption and reaction (SILAR) method for supercapacitor applications. The obtained NCS nanoflowers manifest ultrahigh specific capacitance of 1899 F g−1 at a scan rate of 5 mV s−1. The NCS nanoflowers exhibit a prominent energy density of 55.16 Wh kg−1 at power density of 495 W kg−1 and superior cyclic stability of 94% after 10000 cycles. In addition, the asymmetric supercapacitor (ASC) device is fabricated using NCS nanoflower as positive and reduced graphene oxide (rGO) as negative electrodes, respectively. The ASC (NCS//rGO) delivered good capacity with excellent energy and power densities within 1.6 V wider potential window. Hence, NCS nanoflowers are an outstanding material for energy storage applications in near future.

Herein, we show that DNA nanostructures have great potential as templates for the synthesis of shape-controlled metal nanostructures. In specific, branch-shaped gold nanostructures, which show broad absorption in near the infrared region and have high efficacy in photothermal cancer cell treatment, have been successfully synthesized by using X-shaped and Y-shaped DNA as templates.

Microfluidic devices have been extensively developed as methods for microscale materials fabrication. It has also been adopted for polymeric microsphere fabrication and in situ drug encapsulation. Here, we employed multi-inlet microfluidic channels for DNA hydrogel microsphere formation and in situ protein encapsulation. The release of encapsulated proteins from DNA hydrogels showed different profiles accordingly with the size of microspheres.