Microstructure Of Precursors Research Articles

Characteristics of NaNbO3 templates and improvement of electrical properties of textured KNLNS-BNKT ceramics

In this study, plate-like perovskite NaNbO3 (NN) templates were formed from Bi2.5Na3.5Nb5O18 (BiNN5) precursors via a molten salt method. The structure and microstructure of BiNN5 precursors and NN templates were studied. As a result, the platelike BiNN5 precursor particles have a bismuth layer perovskite structure, which is the basis for forming the synthesized plate-like NN particles that have a high aspect ratio with a width of 2-7 μm, a length of 5-12 μm and a thickness of 0.5-1 μm. From NN templates, we fabricated textured lead-free 0.98(K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O3 − 0.02Bi0.5(Na0.4K0.1)TiO3 (KNLNS- BNKT) ceramic by the grain orientation technique. Experimental results show that the KNLNS-BNKT ceramics have a single-phase orthorhombic structure in which textured KNLNS-BNKT ceramics with 67% grain orientation. The electrical properties of the oriented ceramic are significantly improved compared to the non-oriented ceramic fabricated by the traditional method. Specifically, the electrical properties of the resulting KNLNS-BNKT oriented ceramics have a high dielectric constant (ε = 1323, an increase of 17%); large remnant polarization (Pr = 13.5 mC/cm2, an increase of 11.9%); high piezoelectric coefficient (d33 = 205 pC/N, an increase of 32%) and high electromechanical coupling coefficient (kp = 0.4, an increase of 11%).

Regulating Hetero-Nucleation Enabling Over 14% Efficient Kesterite Solar Cells.

Developing well-crystallized light-absorbing layers remains a formidable challenge in the progression of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. A critical aspect of optimizing CZTSSe lies in accurately governing the high-temperature selenization reaction. This process is intricate and demanding, with underlying mechanisms requiring further comprehension. This study introduces a precursor microstructure-guided hetero-nucleation regulation strategy for high-quality CZTSSe absorbers and well-performing solar cells. The alcoholysis of 2-methoxyethanol (MOE) and the generation of high gas-producing micelles by adding hydrogen chloride (HCl) as a proton additive into the precursor solution are successfully suppressed. This tailored modification of solution components reduces the emission of volatiles during baking, yielding a compact and dense precursor microstructure. The reduced-roughness surface nurtures the formation of larger CZTSSe nuclei, accelerating the ensuing Ostwald ripening process. Ultimately, CZTSSe absorbers with enhanced crystallinity and diminished defects are fabricated, attaining an impressive 14.01% active-area power conversion efficiency. The findings elucidate the influence of precursor microstructure on the selenization reaction process, paving a route for fabricating high-quality kesterite CZTSSe films and high-efficiency solar cells.

Managing ammonia-alkali balance to control precursor characteristics in co-precipitation process for enhanced electrochemical performance of nickel-rich cathode materials

The pH value and total ammonia concentration are critical parameters in the preparation of Ni-rich cathode material precursors by co-precipitation. These parameters play crucial roles in determining the morphological characteristics and crystal structures of the precursors. This paper explores the effects of pH value and ammonia concentration during co-precipitation reactions, examines the relationships between precursor microstructure parameters and macroscopic particle characteristics, and establishes the correlation between the crystal structure of active materials and electrochemical properties alongside precursor particle characteristics. The results demonstrate that the precursors with a higher tap density are more likely to produce nickel-rich active materials with superior crystal structure and electrochemical properties, contingent on the higher pH value and the appropriate ammonia concentration at that pH value. Within the range of experimental conditions in this study, the optimal process conditions were determined to be pH = 11.8 and ammonia concentration = 0.97 mol l−1.

Magnetoelastic coupling and microstructure dynamics associated with spin-orbit coupling in the ferrimagnetic/ferroelastic ordered double perovskite Ba2FeReO6

Strain coupling and relaxation dynamics associated with the ferrimagnetic/ferroelastic phase transition at ${T}_{c}\ensuremath{\approx}310\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ in double perovskite ${\mathrm{Ba}}_{2}{\mathrm{FeReO}}_{6}$ with a high degree of Fe/Re order have been investigated with resonant ultrasound spectroscopy through the temperature interval $\ensuremath{\sim}5--600\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and with applied magnetic field of up to $\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.28em}{0ex}}\mathrm{T}$. Strain analysis using diffraction data from the literature is consistent with a Landau model of the transition as $Fm\overline{3}m{1}^{\ensuremath{'}}\ensuremath{\rightarrow}I4/m{m}^{\ensuremath{'}}{m}^{\ensuremath{'}}$, improperly ferroelastic, driven by a magnetic order parameter with symmetry ${\mathrm{\ensuremath{\Gamma}}}_{4}^{+}$. Ferroelastic shear strain of up to $\ensuremath{\sim}0.0015$ arises from spin/orbit coupling and is smaller than is typical of coupling with octahedral tilting. It provides the underlying cause of softening of the shear modulus observed over an interval of $\ensuremath{\sim}100\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ below ${T}_{\mathrm{c}}$, though with order/disorder rather than displacive character for the transition. Hysteretic effects suggest that precursor microstructures and mixed magnetic/ferroelastic domains below ${T}_{\mathrm{c}}$ depend on the thermal history of the sample and can evolve on a timescale of hours and days at room temperature. Elasticity data collected as a function of external magnetic field reveal that poled samples are slightly softer than those with multiple magnetic domains at 4 K. At 300 K there is a time-dependent viscous component of the response to the field that relates to the bulk modulus and, hence, to volume changes associated with magnetic ordering. A loss peak seen $\ensuremath{\sim}20--50\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ below ${T}_{\mathrm{c}}$ in AC magnetic measurements made at frequencies of $0.2--1\phantom{\rule{0.28em}{0ex}}\mathrm{kHz}$ yielded an activation energy $\ensuremath{\sim}0.4\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ and has been attributed to freezing of magnetic/ferroelastic domain walls. No equivalent loss peak was seen in the acoustic data measured at $\ensuremath{\sim}100--500\phantom{\rule{0.28em}{0ex}}\mathrm{kHz}$, however, implying that these domain walls are mobile in response to a dynamic magnetic field on a timescale of $\ensuremath{\sim}{10}^{\ensuremath{-}2}\text{--}{10}^{\ensuremath{-}3}\phantom{\rule{0.28em}{0ex}}\mathrm{s}$ but immobile in response to a dynamic stress field applied on a timescale of $\ensuremath{\sim}{10}^{\ensuremath{-}5}\text{--}{10}^{\ensuremath{-}6}\phantom{\rule{0.28em}{0ex}}\mathrm{s}$. Debye-like acoustic loss peaks at temperatures below $\ensuremath{\sim}100\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ yielded activation energies of $\ensuremath{\sim}0.02--0.1\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ and are discussed in terms of pinning/freezing of polarons. ${\mathrm{Ba}}_{2}{\mathrm{FeReO}}_{6}$ is a material with magnetoelastic and magnetoelectric heterogeneities that might be tuned by choice of thermal history and cation order.

The mitigation of pitch-derived carbon with different structures on the volume expansion of silicon in Si/C composite anode

The microstructures of carbon precursors significantly affect the electrochemical performance of Si/C composite anodes. However, the interaction between Si and carbon materials with different structures is still unclear. Pitch-based materials undergoing different thermal treatments are superior sources for synthesizing carbons with different structures. Herein, different types of mesophase pitch (domain, flow-domain and mosaic structure) obtained from controllable thermal condensation are utilized to prepare Si/C composite materials and the corresponding models are established through finite element simulation to explore the correlation between the lithium storage properties of Si/C composites and the structures of carbon materials. The results indicate that the flow-domain texture pitch P2 has a better ability to buffer the volume expansion of silicon particles for its highly ordered arrangement of carbon crystallites inside could disperse the swelling stress uniformly alongside the particle surface. The sample Si@P2 exhibits the highest capacity of 1328 mA h/g after 200 cycles at a current density of 0.1 A/g as well as the best rate performance and stability. While sample Si@P3 in which the mosaic texture pitch P3 composed of random orientation of crystallites undergoes the fastest capacity decay. These findings suggest that highly ordered carbon materials are more suitable for the synthesis of Si/C composite anodes and provide insights for understanding the interaction between carbon and silicon during the charging/discharging process.

Microstructure and phase evolution behavior of SiZrBC ceramic precursors synthesized via sol–gel method

ZrB2–SiC ceramics were successfully prepared via sol–gel method using phenyltrichlorosilane, borane dimethyl sulfide, and zirconium tetrachloride in stoichiometric amounts as the raw materials. The macromolecular network structure formed after the sol–gel process was investigated via Fourier transform infrared (FT–IR) spectroscopy. The phase evolution of the ZrB2–SiC ceramics were analyzed by FT–IR spectroscopy, X–ray diffraction, and transmission electron microscopy, whereas morphological and elemental analyses were performed using scanning electron microscopy. In particular, the change in phase composition was monitored after the pyrolysis from 1400 to 1500 ​°C, and the heat treatment of BZ6 precursor at 1500 ​°C enabled one to produce the ZrB2–SiC ceramic with a homogeneous crystal phase distribution. Therefore, the controllable microstructure adjustment of the ceramic phase composition could be achieved and a new way was paved for the structural and functional applications of ultra–high–temperature ceramics (UHTCs) series.

Homogeneously Nitrogen Doped BaLa4Ti4O15Extending Visible Light Responsive Range for Photocatalytic Oxygen Evolution

Homogeneous nitrogen doping is a promising strategy for narrowing the band gap of layered metal oxides without altering the crystal structures and microstructures of precursors. In this work, BaLa4Ti4O15, a (111) plane-type layered perovskite metal oxide with a band gap of about 3.77 eV, was doped with nitrogen by a thermal treatment in an ammonia atmosphere. The nitrogen dopants are homogeneously distributed in the layered perovskite framework, resulting in an extended band-to-band visible light absorption edge up to 600 nm, corresponding to a band gap of 2.07 eV. It is worth noting that the nitrogen doping process has trivial impact on the crystal structure, microstructure, and chemical states of the BaLa4Ti4O15, which minimizes the side effect of photogenerated carrier separation and surface chemical reaction. BaLa4Ti4O15–xNy exhibited efficient photocatalytic water oxidation activity under visible light. This work highlights the usefulness of homogeneous doping for tuning wide band gap layered metal oxides.

Evolution of a Radially Aligned Microstructure in Boron-Doped Li[Ni0.95Co0.04Al0.01]O2 Cathode Particles.

Boron (B) (1.5 mol %) is introduced into Li[Ni0.95Co0.04Al0.01]O2 (NCA95) to create a radially oriented microstructure with a strong crystallographic texture. The cathode microstructure allows dissipation of the abrupt lattice strain near the charge end and improves the cycling stability of the NCA95 cathode (88% capacity retention after 100 cycles at 0.5 C). Transmission electron microscopy (TEM) analysis of the B-doped NCA95 cathode during lithiation reveals that the highly oriented microstructure is provided by a hydroxide precursor. Boron prevents random agglomeration of the primary particles and keeps them elongated through (003) faceting. The selected-area electron diffraction analysis shows that the structure of the lithiated oxide undergoes subtle structural changes even after the crystal structure is fully converted from P3̅m1 to R3̅m at 600 °C. Li+/Ni2+ intermixing is prevalent due to the slow oxidation of Ni2+ to Ni3+. Li+ and Ni2+ do not randomly occupy the Ni and Li layers; instead, these ions occupy their sites in an ordered pattern, forming a superlattice. The superlattice gradually disappears as the lithiation temperature is increased. One peculiar structural feature observed during lithiation is the prevalence of twin defects that preexist in the hydroxide precursor as growth twins. The twin defects, which could serve as nucleation sites for intraparticle cracks, also gradually anneal out during lithiation. TEM analysis substantiates the importance of the hydroxide precursor microstructure in a coprecipitation process and provides a basis for choosing the appropriate lithiation temperature and soaking time to obtain the desired cathode structure and primary particle morphology.

Inhomogeneous dealloying kinetics along grain boundaries during liquid metal dealloying

In this study, the inhomogeneous dealloying phenomenon during the liquid metal dealloying (LMD) was investigated using Fe50Ni50+Mg and (FeCo)50Ni50+Mg systems. For the Fe50Ni50+Mg system, the inhomogeneous dealloying and wetting of Mg melt occurred along triple junction (TJ) and grain boundary (GB). Temperature increase enhances the inhomogeneous dealloying kinetics and leads to the formation of the plate-shaped abnormal ligaments at the GB region. The energy banlance between a GB energy (γGB) and solid-liquid interface energies (γsl) is the key factor governing the inhomogeneous dealloying and wetting. Particularly, the low-energy twin boundaries were unaffected by the inhomogeneous dealloying. Therefore, precursor microstructure is an important factor determining the final morphology of dealloyed material as well as its physical properties. In the case of the (FeCo)50Ni50 precursor, all TJ and GB were stable against the preferred penetration of Mg melt from 600 °C to 800 °C. It was concluded that a minor addition of alloying elements (V or Cr) changes GB characteristics as well as γsl of the precursor alloy. Consequently, this significantly influences dealloying mechanisms and final morphology of the dealloyed material. The current findings demonstrate the importance of GB engineering in the precursor materials for the technological application of liquid metal dealloying for the synthesis of advanced structural and functional materials.

Kirkendall synthesis and characterization of nanotubular (Bi2)m(Bi2Te3)n series

The (Bi2)m(Bi2Te3)n series, as well-studied thermoelectric materials, have also attracted worldwide attention for their unique topological insulator property. However, only one of several compounds in the Bi-Te systems is synthesized, especially for one-dimensional structures. Herein, a two-step solvothermal process has been designed to synthesize nanotubular (Bi2)m(Bi2Te3)n series (i.e., Bi2Te3, Bi4Te3, BiTe, and Bi2Te3-Te) by optimizing the concentration of Bi agent and altering the microstructure of Te precursors during the reaction process regarding “Kirkendall effect”. The results were verified by powder X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDS), high-resolution transmission electron microscope (HR-TEM), selected area electron diffraction (SAED), and inductively coupled plasma optical emission spectrometer (ICP-OES). A possible growth mechanism was proposed based on experimental results. This work provides a feasible way to selectively synthesize (Bi2)m(Bi2Te3)n compounds with tunable composition and structure.

Examining the Ability of Aerobic Halophilic Heterotrophic Microbial Consortia to Replace Ca by Mg in Different CaCO3 Precursors.

Recent laboratory experiments have exhibited microbes as promising agents in solving the perplexing origin of ancient dolomite by demonstrating microbial capability to mediate dolomite nucleation and growth. However, dolomite crystals from laboratory experiments have shown irrelevant characteristics to ancient dolomite from mineralogical and petrological perspectives. A major irrelevant characteristic is that ancient dolomite was assumed to be formed after the replacement of Ca by Mg in precursor CaCO3 in a process known as diagenesis, which contrasts with the primary precipitation process observed in laboratory culturing experiments. Considering dolomite microbial experiments, one can imply the involvement of microbes in the formation of ancient dolomite, as microbes have shown the ability to overcome the dolomite kinetic barrier. Despite that fact, the ability of microbes in mediating dolomite diagenesis has not been investigated. In this study, microbes were applied to mediate replacement of Ca by Mg in different CaCO3 precursors. The microbial replacement experiments were based on the enrichment of aerobic halophilic heterotrophic microbial consortia sampled from sediments collected from Al-Subiya sabkha in Kuwait. Two experiments were performed in saturated media at 35°C for 14 and 30 days simulating the conditions of microbial dolomite experiments. The change in mineralogy was examined via powder X-ray diffraction (XRD), and the change in texture and compositional microstructures was examined using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). The effect of microbes on the alteration of CaCO3 precursors was studied by comparing biotic experimentations with abiotic controls. The biotic samples were shown to result in the favorable conditions for dolomite formation including an increase in pH and alkalinity, but no changes were observed in mineralogy or compositional microstructure of CaCO3 precursors. Our results suggest the inability of aerobic halophilic heterotrophic microbial consortia to introduce Mg replacement on CaCO3 precursors in a timely manner that is comparable to primary precipitation in microbial dolomite experiments. The inability of the enriched microbial consortia to mediate replacement can be ascribed to different factors controlling the diagenetic process compared to primary precipitation in microbial dolomite experiments.

Improvement of Mechanical Properties of a Medium-Mn TRIP Steel by Precursor Microstructure Control

Improvement of Mechanical Properties of a Medium-Mn TRIP Steel by Precursor Microstructure Control

Role of precursor microstructure in the development of graphene quantum dots from biomass

Renewable, green and cheap biomass could meet the urgent need of cost-effective graphene quantum dots (GQDs) if microstructure and quality can be precisely controlled. Herein, for the first time, we investigate the effect of precursor microstructure on the growth of GQDs from biomass. A novel process is developed which combines carbonisation, oxidation and nitration with controlled hydrothermal fragmentation to form GQDs. The results indicate that aromatic structure of carbon material as a precursor is the key to obtain high-quality GQDs. The as-prepared GQDs possess a 3–9 layer graphene structure with an average size of 11.6 ± 1.8 nm and exhibit a moderate quantum yield of 17.5%. These GQDs are used to develop a highly selective and sensitive sensor to detect ferric ions with a detection limit as low as 26 ± 0.4 nM. This study highlights the development of high quality GQDs from biomass for real-world sensing, photocatalytic and biomedical applications.

Growth mechanisms for spherical Ni0.815Co0.15Al0.035(OH)2 precursors prepared via the ammonia complexation precipitation method

The crystal habit is essential to the Li-storage property for Ni-rich cathode materials. In this study, the growth behaviour of Ni 0.815 Co 0.15 Al 0.035 (OH) 2 prepared via the ammonia complexation precipitation method in the CSTR is studied in detail. The microstructures of precursors strongly affect the electrochemical performance of Ni-rich layer-structured cathode materials. In this study, the growth behaviour of Ni 0.815 Co 0.15 Al 0.035 (OH) 2 (NCA) prepared via the ammonia complexation precipitation method in a 50-L-volume continuously stirred tank reactor (CSTR) is studied in detail. The growth of Ni(OH) 2 -based hydroxide can be divided into a nucleation process, an agglomeration growth process, a process in which multiple growth mechanisms coexist, and an interface growth process over time, while the inner structure of the CSTR can be divided into a nucleation zone, a complex dissolution zone, a growth zone, and a maturation zone. The concentration of ammonium ions affects the growth habit of the primary crystal significantly due to its specific adsorption on the electronegative crystal plane. When the ammonia concentration is <1.5 mol L −1 at 60 °C at pH = 11.5, the precursors grow preferentially along the (1 0 1) crystal plane, whereas they grow preferentially along the (0 0 1) crystal plane when the concentration is >2.0 mol L −1 . The LiNi 0.815 Co 0.15 Al 0.035 O 2 materials inherit the grain structure of the precursor. Materials prepared from precursors with (1 0 1) preferential primary particles show a higher specific capacity and better rate performance than those that were prepared from (0 0 1) preferential primary particles, but the latter realize a better cycling performance than the former.

Effect of precursor microstructure on the performance of LiNi0.85Co0.10Mn0.05O2 cathode materials

Effect of precursor microstructure on the performance of LiNi0.85Co0.10Mn0.05O2 cathode materials

A routine for the determination of the microstructure of stacking-faulted nickel cobalt aluminium hydroxide precursors for lithium nickel cobalt aluminium oxide battery materials.

The microstructures of six stacking-faulted industrially produced cobalt- and aluminium-bearing nickel layered double hydroxide (LDH) samples that are used as precursors for Li(Ni1-x-yCo x Al y )O2 battery materials were investigated. Shifts from the brucite-type (AγB)□(AγB)□ stacking pattern to the CdCl2-type (AγB)□(CβA)□(BαC)□ and the CrOOH-type (BγA)□(AβC)□(CαB)□ stacking order, as well as random intercalation of water molecules and carbonate ions, were found to be the main features of the microstructures. A recursive routine for generating and averaging supercells of stacking-faulted layered substances implemented in the TOPAS software was used to calculate diffraction patterns of the LDH phases as a function of the degree of faulting and to refine them against the measured diffraction data. The microstructures of the precursor materials were described by a model containing three parameters: transition probabilities for generating CdCl2-type and CrOOH-type faults and a transition probability for the random intercalation of water/carbonate layers. Automated series of simulations and refinements were performed, in which the transition probabilities were modified incrementally and thus the microstructures optimized by a grid search. All samples were found to exhibit the same fraction of CdCl2-type and CrOOH-type stacking faults, which indicates that they have identical Ni, Co and Al contents. Different degrees of interstratification faulting were determined, which could be correlated to different heights of intercalation-water-related mass-loss steps in the thermal analyses.

Tailoring of an unusual oxidation state in a lanthanum tantalum(IV) oxynitride via precursor microstructure design

Perovskite-type oxynitrides hold great potential for optical applications due to their excellent visible light absorption properties. However, only a limited number of such oxynitrides with modulated physical properties are available to date and therefore alternative fabrication strategies are needed to be developed. Here, we introduce such an alternative strategy involving a precursor microstructure controlled ammonolysis. This leads to the perovskite family member LaTa(IV)O2N containing unusual Ta4+ cations. The adjusted precursor microstructures as well as the ammonia concentration are the key parameters to precisely control the oxidation state and O:N ratio in LaTa(O,N)3. LaTa(IV)O2N has a bright red colour, an optical bandgap of 1.9 eV and a low (optically active) defect concentration. These unique characteristics make this material suitable for visible light-driven applications and the identified key parameters will set the terms for the targeted development of further promising perovskite family members.

Effect of process factors on properties of high dispersion spherical α-Al2O3 particles prepared by hydrothermal method

Spherical α-Al2O3 powders were synthesized from a mixed solution consisting of Al2(SO4)3·18H2O, Al(NO3)3·9H2O and CH4N2O by hydrothermal method with muffle calcination and microwave calcination. Effects of raw material ratio, reaction temperature, and filling factor on properties of products were investigated. Properties of thermal behavior, functional groups, phase composition, microstructure and specific surface of precursors and products were characterized by DSC-TG, FT-IR, XRD, SEM and BET, respectively. Results show that SO42− plays an important role in the sphere formation of precursors and particle size can be changed by adding different proportion of NO3−. Precursors are amorphous spherical hydrated alumina containing SO42−, and the conversion of crystalline phase is from amorphous to γ-phase and then to α-phase at 1100 °C. Spherical morphology can be retained after crystallization to α-Al2O3. Compared with muffle furnace, Microwave calcination can increase calcining rate by three times and reduce insulation time by three quarters. When hydrothermal reaction temperature is 120 °C, the particles can be precipitated with good sphericity and narrow grain size distribution. If hydrothermal reaction temperature is too high or too low, spherical morphology can't be obtained. Size of the particles can be regulated by the different raw material ratio and filling factor from 800 nm to 3 μm, and specific surface area is in the range of 8 m2/g~15 m2/g.

Reactive sites rich porous tubular yolk-shell g-C3N4 via precursor recrystallization mediated microstructure engineering for photoreduction

Photoabsorption, charge separation efficiency and surface reactive catalytic sites are three critical factors in semiconductor photocatalytic process, which determine the photocatalytic activity. For bulk g-C3N4 derived from direct pyrolysis of C/N rich precursors, reactive sites distributed on the lateral edges are very scarce. In this work, we report the template-free preparation of three novel structured g-C3N4, namely, porous tubular (PT) g-C3N4, porous tubular yolk-shell (PTYS) g-C3N4, and porous split yolk-shell (PSYS) g-C3N4, by an unprecedented precursor microstructure regulation of melamine crystals in a gas-pressure mediated re-crystallization process. Enhanced photoabsorption, increased surface area, largely improved separation and migration efficiencies of photoinduced charge carriers are simultaneously realized in these g-C3N4 structures. Noticeably, selective photo-deposition test uncovers that the porous outer-walls and inner-rods of PTYS g-C3N4 are enriched by abundant reductive reactive sites, which consumedly boost the photo-reduction activity. Collectively promoted by these advantages, PTYS g-C3N4 shows not only an efficient H2 production activity with a high apparent quantum efficiency (AQE) of 11.8% at λ = 420 ± 15 nm, but also a superior CO2 reduction for CO production than bulk g-C3N4 by a factor 5.6, which is verified by the 13C isotopic labeling. This work develops precursor microstructure engineering as a promising strategy for rational design of unordinary g-C3N4 structure for renewable energy production.

Microstructure Development of Full Concentration Gradient Li[Ni0.75Co0.10Mn0.15]O2 Cathode for Lithium-Ion Batteries

Detailed analysis of the microstructural changes during lithiation of a full-concentration-gradient (FCG) cathode with an average composition of Li[Ni0.75Co0.10Mn0.15]O2 was performed starting from its hydroxide precursor, FCG [Ni0.75Co0.10Mn0.15](OH)2 prior to lithiation. Transmission electron microscopy (TEM) revealed that a unique rod-shaped primary particle morphology and radial crystallographic texture were present in the pre-lithiation stage. In addition, TEM detected a two-phase structure consisting of MnOOH and Ni(OH)2, and crystallographic twins of MnOOH on the Mn-rich precursor surface. The formation of numerous twins, driven by the lattice mismatch between MnOOH and Ni(OH)2, resulted in crenellated surfaces. Furthermore, the twins persisted in the lithiated cathode; however, their density decreased with increasing lithiation temperature. Cation disordering, which influences cathode performance, was observed to continuously decrease with increasing lithiation temperature with a minimum observed at 790 °C. Consequently, lithiation at 790 °C (for 10 h) produced optimal discharge capacity and cycling stability. Above 790 °C, an increase in cation disordering and excessive coarsening of the primary particles led to the deterioration of electrochemical properties. It is conjectured that the twins in the FCG cathode precursor promoted the optimal primary particle morphology by retarding the random coalescence of primary particles during lithiation, effectively preserving both the morphology and crystallographic texture of the precursor. Furthermore, the effects of the precursor microstructure and subsequent final primary particle morphology on the optimal lithiation schedule and cation disordering were determined. Y.-K. Sun, S.-T. Myung, B.-C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater. 2009, 8, 320. J. H. Lee, C. S. Yoon, J.-Y. Hwang, S.-J. Kim, F. Maglia, P. Lamp, S.-T. Myung, Y.-K. Sun, Energy Environ. Sci. 2016, 9, 2152. U.-H. Kim, E.-J. Lee, C. S. Yoon, S.-T. Myung, Y.-K. Sun, Adv. Energy Mater. 2016, 6, 1601417. C. S. Yoon, K.-J. Park, U.-H. Kim, K. H. Kang, H.-H. Ryu, Y.-K. Sun, Chem. Mater. 2017, 29, 10436.