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Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes. To address these issues, we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny silicon particles as the core assisted by small amount of SiC. Skillfully exploiting the high heat from magnesiothermic reduction, SiC can assist the good dispersion of silicon and provide good interface compatibility and chemical stability. The silicon anchored to the carbon shell provides multipoint contact mode, that together with the carbon shell frame, significantly promoting the transfer of dual charge. Besides, the pomegranate-type microcluster structure also improves the tap density of the electrode, reduces the direct contact area between active material and electrolyte, and enhances the electrochemical performance.

To improve the stability of molybdenum carbide catalysts in dimethyl ether steam reforming (DSR), the inactivation mechanism and the performance of Pt modified catalyst has been investigated. The Mo2C oxidation induced by H2O is verified to be the main reason of catalytic deactivation. After modified with Pt, the H2 production rate and selectivity are greatly enhanced, reaches 1605 μmol min−1·gcat−1 at 350 °C, in comparison to that of the Mo2C/Al2O3 catalyst. Moreover, the 2%Pt–Mo2C/Al2O3 catalyst is more stable with only 20% activity loss after 50 h on stream compares to the 73% activity loss in 12 h with Mo2C/Al2O3 catalyst. By means of in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the enhancement brought by Pt is ascribed to the consumption acceleration of intermediate oxygen species on catalyst surface and the decline of onset temperature of DSR reaction. It is expected that these findings can lead us to more practical molybdenum carbide catalysts in DSR.

Doping multielectronic elements into carbon materials is an effective method to improve their electrochemical performance, as it can not only improve the electrical conductivity of the material, but also capture more lithium ions when they are involved in Li-ion battery. Here, using flour as biomass carbon source, the chlorine/phosphorus dual-elements doped porous carbon materials are obtained by pyrolysis at 800 °C and hydrochloric acid treatment. The introduction of chlorine can significantly increase the capacity of carbon materials. Importantly, the hydrogen in mixed gas during heat treatment process can increase the degree of ordered carbon, which led to the improvement of material conductivity and the ability of lithium ions intercalation, further improving the cycling performance and rate performance. Under the current density of 0.2 A g−1, it can remain 535.2 mAh g−1 after 200 cycles. And after two months resting, the capacity only decline by 5.9%, and can still keep the stable cycling performance to 500 cycles. The simple and low cost design of carbon is a creative and promising candidate for anode materials of high performance Li-ion batteries.

In this work, PtCo nanoparticles (NPs) on hierarchically ordered mesoporous carbon (PtCo/OMC) are synthesized for polymer electrolyte membrane fuel cells (PEMFCs) aiming to improve the activity and durability of the Pt-based catalyst towards oxygen reduction reaction (ORR). Specifically, the OMC is prepared through a solvent evaporation-induced self-assembly (EISA) method by using a triblock copolymer PEO-PPO-PEO as the structure agent, followed by annealing in the nitrogen atmosphere to decompose the structure agent and to carbonize the carbon precursor. PtCo nanoparticles (NPs) are fabricated with an average diameter of 3.3 nm by H2 reduction and galvanic replacement in an acid solution, and then are uniformly dispersed onto the OMC via impregnation. The typical mesoporous structure of the OMC enhances the uniformly distribution and thermal stability of the small-sized PtCo NPs. The activity and the durability of the as-prepared PtCo/OMC catalyst are investigated by cyclic voltammetry (CV) and single-cell test. In the electrochemical tests, PtCo/OMC exhibits a high ECSA value of 88.56 m2g−1, and a ECSA retention of 77.5% after 5000 CV cycles. The results show that the PtCo/OMC catalyst is more active and more stable than the commercial-carbon-supported PtCo catalyst (PtCo/XC-72). PtCo nanoparticles (NPs) on hierarchically ordered mesoporous carbon (PtCo/OMC) are synthesized aiming to improve the activity and stability of the Pt-based catalyst for the oxygen reduction reaction (ORR). Due to the natural mesoporous and graphite-carbon nanostructure of the OMC, the as-prepared PtCo/OMC catalyst is more active and more stable than the PtCo NPs on the commercial Vulcan@ XC-72 support (PtCo/XC-72), showing great potential in proton exchange membrane fuel cells (PEMFCs).

Perovskite ferroelectric oxides are usually considered to be brittle materials; however, recent work [Dong et al., Science 366, 475 (2019)] demonstrated the super-elasticity in the freestanding BaTiO3 thin films. This property may originate from the ferroelectric domain evolution during the bending, which is difficult to observe in experiments. Therefore, understanding the relation among the bending deformation, thickness of the films, and domain dynamics is critical for their potential applications in flexible ferroelectric devices. Here, we reported the dynamics of ferroelectric polarization in the freestanding BaTiO3 ultrathin films in the presence of large bending deformation up to 40° using phase-field simulation. The ferroelectric domain evolution reveals the transition from the flux-closure to a/c domains with “vortex-like” structures, which is caused by the increase in out-of-plane ferroelectric polarization. Additionally, by varying the film thickness in the identical bending situation, we found that the a/c phase with a vortex-like structure emerges only as the film thickness reached 12 nm or higher. The results from our investigations provide instructive information for the microstructure evolution of bending ferroelectric perovskite oxide films, which could serve as a guide for the future application of ferroelectric films on flexible electronic devices.

Self-assembly of di-blcok copolymers (di-BCs) with precise control on morphologies and structures of nanomaterials makes it a promising technology for catalyst preparation. However, applications of the BC-synthesized Pt nanoparticles (NPs) on fuel cell have less been discussed. The major challenge may be the difficulty in achieving high-density nanopatterns which require a low degree of polymerization but a high effective segment-segment interaction parameter of the BC templates. As a resolution, sequentially double- or triple-layered BC route provides a new density-increased idea of harnessing these materials. In present work, monolayer of ordered and high-dispersed Pt-NP arrays with a density 27-folded has been achieved by the multiple di-BC routes consisted of identical self-assembly and plasma-cleaning processes. The multiplication has been proved to be equivalent to the duplication and oriented translation of the initial Pt-NP arrays, which provides not only a well-defined approach to control the spacing precisely, but also a bottom-up process to synthesize hexagonal-arranged arrays with predicable densities. Electrochemistry shows that the density multiplication has no negative effects on the Pt utilization of the monolayer arrays, and a remarkable ECSA value of ∼114.5 m2 g−1 is found. Further characterization of the monolayer arrays as cathodic catalysts for PEMFC reveals that, neither the ohmic losses nor the mass-transport losses are enhanced after the density multiplication, and the power density of the PEMFC assembled here is significantly higher than that using commercial Pt/C catalysts. All the results demonstrate that the multiple di-BC approach has great potential in preparation of BC-synthesized Pt-NP arrays for fuel cell applications.

A series of Ni-modified Mo2C catalysts with La2O3-stabilized ZrO2 supports were synthesized via template method coupled with incipient wetness impregnation and temperature-programmed carbonization. The catalyst was tested in dry reforming of methane (DRM) reaction at the temperature range from 973 to 1173 K in a fixed-bed quartz reactor under atmospheric pressure. XRD, Raman, BET, H2-TPD, SEM, EDS and TEM were conducted to characterize the phase constitution, the pore structure, the morphology and the crystal structure of the catalysts. Ni–Mo2C nanoparticles of ~ 3 nm diameter were obtained for these catalysts, and the La2O3–ZrO2 supports exhibited a cubic lattice structure with a sheet shape, which is believed to contain an abundant of oxygen vacancies. And the synergistic interaction between the oxygen vacancy in La–Zr–O solid solution and the Ni–Mo2C particles could decrease the apparent activation energy of CO2. Both of them are beneficial for accelerating DRM reaction. CH4 conversion of the best specimen catalyst reaches 94% at 1173 K, and the catalyst maintains its stability after 100-h reaction. The superior catalytic activity of NMLZ-7.5 is attributed to the improved BET surface area (33.2 m2/g), smaller crystallites, grain boundaries and oxidation–carbonization cycle of Ni–Mo2C.

To fabricate effective and stable OER electrode in water electrolysis, self-doped TiO2 nanotube arrays which has a higher electrical conductivity than pristine TiO2 nanotube arrays was used as the support for loading IrO2. The self-doped TNTA was fabricated by a simple electrochemical reduction of TNTA in neutral electrolyte solution, and then IrO2 nano particles were deposited by pulse electro-deposition method. The cyclic voltammetric behavior, electrical conductivity and micro structure of self-doped TNTA prepared at different reduction potential were characterized to obtain an optimal performance, and self-doped TNTA prepared under −1.9 V (vs. Ag/AgCl) shows the best electrochemical performance. After depositing IrO2, the OER activity and stability of new electrodes were also determined. Due to the enhanced electrical conductivity of support, the mass activity of IrO2/self-doped TNTA are 50 times higher than IrO2/TNTA. The OER stability of new electrode was evaluated under constant current of 5 mA/cm2, IrO2/TNTA and IrO2/Ti were also tested for comparison. A higher stability of IrO2/self-doped TNTA electrode is observed than the other two electrodes, and XPS studies indicate a lower oxidation state of Ir in IrO2/self-doped TNTA, this shows a possible interactions between IrO2 and the new support.

Efficient and rapid separation of emulsified oil/water mixtures is urgently needed and still remains a worldwide challenge. Even though traditional superhydrophobic/superoleophilic filtration membranes have demonstrated to be effective for separation of water-in-oil emulsions, they still suffer from complicated fabrication procedures and lower flux, resulting from their nanoscale pore size. Herein, green desert sands (50 μm to 1 mm) with under-oil superhydrophilicity were introduced, for the first time, to develop into a layer for efficient gravity-directed separation of various water-in-oil emulsions, which could avoid not only sophisticated filtration membranes fabrication process but also the use of expensive low energy materials of fluorosilane involved in traditional superhydrophobic materials. It is worth mentioning that the sand layer could serve as an adsorbent material with under-oil superhydrophilicity, achieving ultrafast gravity-driven separation of tiny water droplets from various water-in-oil emulsions with flux as high as 2342 L m−2 h even though the interspacing between the sand particles is greater than the size of emulsified droplets. Moreover, the sand can be abundantly obtained from deserts, which is another advantage that the current filtrate materials do not possess. In summary, this study provides a general avenue to design under-oil superhydrophilic materials for rapid separation of water-in-oil emulsions. Such an approach can provide some new perspectives for fabrication of novel emulsion-separating materials.

The interactions of formaldehyde (HCHO) molecule with TiO2 (001) surface were studied using density functional theory calculations. HCHO molecules are dissociated by the cleavage of C H bonds after adsorption on TiO2 surface. The strong interactions between HCHO melecules and TiO2 surface are largely attributed to the bonding of hydrogen of HCHO and oxygen of TiO2 surface, which is mainly from the hybridization of the H 1s, O 2p and O 2s. The newly formed H O bonds cause the structure changes of TiO2 surface, and lead to the cleavage of O Ti bond of TiO2 surface. The C O bond that the dissociated remains of HCHO and newly formed H O bond can be oxidized to form carbon dioxide and water in subsequent action by oxygen from the atomosphere. The charges transfer from HCHO to TiO2 surface, and the sum amount of the charges transferred from four HCHO molecules to TiO2 surface is bigger than that from one HCHO molecule to TiO2 surface due to the combined interaction of four HCHO molecules with TiO2 surface.

This work offers an effective size-controlled synthesis of platinum nanoparticle (Pt NP) arrays for electrocatalyst through self-assembled nanopatterns of block copolymers on titanium (Ti) wafers. Size, spacing and uniformity of Pt NP with loading of Pt to a minimum were investigated to be controlled and adjusted in order to improve the electrochemically active surface area (ECSA) and ECSA stability, and Pt concentration in copolymer/chloroplatinic acid (H2PtCl6) solution was verified to be one of the most important factors to control the arrays’ structure. In our case, the Pt NPs with predictable size of 5–16.5 nm could be obtained when the Pt concentration is larger than 0.05 mg ml−1, which the dominant diameter is proved to be proportional to one-third power of the Pt concentration according to the linear relation of templates’ Pt/N mass ratio versus Pt concentration, and the Pt NPs remain highly ordered arrays with predictable spacing when the Pt concentration is larger than 0.125 mg ml−1. Decrease in Pt concentration from 2 to 0.125 mg ml−1 is an effective method to improve the ECSA and durability simultaneously. The Pt NP arrays exhibit not only a remarkable initial ECSA value of 106.2 m2 g−1, but also a pseudo-zero particle aggregation possibility during 3000-cycle voltammetry, which is attributed to the high Pt NP dispersion and the ordered arrays that improve the Pt utilization and lower the possibility of aggregation.

Ni/CeO 2 -ZrO 2 was encapsulated by SiO 2 layer with expectation to obtain a high active catalyst for steam reforming of toluene. The coating structure was validated by X-ray diffraction experiments and electron microscope analysis. XPS data suggests the formation of a new Ni-O-Si configuration in core-shell catalysts. The presence of Ni-O-Si configuration shift electron from Ni to silica and thereby facilitates the intrinsic properties of catalysts. Compared to Ni/CeO 2 -ZrO 2 , turnover rate of Ni increased substantially in core-shell structures, Ni/CeO 2 -ZrO 2 @SiO 2 with shell-to-core mass ratio as 1.0 showed about 5.5 times higher than the Ni/CeO 2 -ZrO 2 catalyst.

Sorption enhanced steam reforming of acetic acid over sorbent assisted catalyst of Ni-CaO-La2O3 were investigated for high-purity H2 production. Ni-CaO-La2O3 with 8, 16 and 20 wt% Ni were developed by sol-gel combustion synthesis and were characterized by TG, TPR, BET, SEM, XRD and XPS. The catalytic activities and stability of the catalysts were tested in a fixed reactor. H2 yield and H2 concentration through Ni-CaO-La2O3 with 20 wt% Ni reaches 86.02% and 92.24% during pre-breakthrough period, respectively, which is attributed to sufficient Ni active sites on the surface and good Ni dispersion. Catalytic activities of Ni-CaO-La2O3 with 20 wt% Ni maintain stable during sorption-enhanced steam reforming reaction, but CO2 sorption capacity slightly decreases due to blockage of pores and size increase of CaO particles within nine sorption/desorption cycles.

Porous silica coated Ni/CeO 2 ZrO 2 catalysts were synthesized for steam reforming of acetic acid. The silica coated Ni/CeO 2 ZrO 2 catalyst showed a significantly enhanced activity (95% acetic acid conversion) than the Ni/CeO 2 ZrO 2 catalysts (62% acetic acid conversion) at a low temperature (550 °C). Interaction between Ni/CeO 2 ZrO 2 and silica layer was proved to be a crucial role on enhancing of catalytic activities. Further characterization (XPS, H 2 -TPR) indicates this interaction facilitates the steam reforming reaction and raises the selectivity of CO by modifying the surface Ni electronic structure. In addition, the coated catalyst also exhibited a good stability and no obvious deactivation was detected at 550 °C and 600 °C within 30 h.

A multistep synthesis method is introduced to fabricate high performance IrOx/W-TiO2 catalyst for noble metal reduction in PEM water electrolyzers. The performances of the IrOx/W-TiO2 catalyst for oxygen evolution reaction (OER) are measured in half-cells and single-cells and compared with unsupported IrOx and commercial IrO2. In half-cell tests, IrOx/W-TiO2 displays an improved Ir mass activity compared with the unsupported IrOx, demonstrating a positive effect of the support material. In single-cell tests, the performance of IrOx/W-TiO2 also exceeds both the unsupported and commercial IrO2. The cell voltage reaches 1.602V at 1 A cm−2 (Nafion 212) with total noble metal loading less than 0.2 mg cm−2, suggesting that significant Ir reductions are possible by using IrOx/W-TiO2 without sacrificing the cell performance. It also shows improved durability than other unsupported catalysts at reduced Ir loading. In-situ electrochemical test reveals that the performance is associated with the enhanced conductivity of the catalyst layer.

IrO2 was electro-deposited on hydrogenated TiO2 nanotube arrays (TNTA) to form IrO2/H-TNTA for oxygen evolution reaction (OER). Hydrogenation by calcining in H2 atmosphere was conducted to improve the electric conductivity, which was owing to partially reduce of Ti4+ in TNTA. It was found that hydrogenated TiO2 can facilitate the electro-deposition of IrO2, and elevate the OER activity compared to that of non-calcined and air-calcined TNTA, which would be due to the improved conductivity of H-TNTA. IrO2/H-TNTA shows a five-fold higher activity than IrO2/air-TNTA with the same loading amount. The coverage of IrO2 on the surface of hydrogenated TNTA is crucial to the stability of catalyst and with the increased loading amount of IrO2, IrO2/H-TNTA shows much higher stability.

Hydrogen production from steam reforming of acetic acid was investigated over Ni/La2O3-ZrO2 catalyst. A series of Ni/La2O3-ZrO2 catalysts were synthesized by sol-gel method coupled with wet impregnation, which was characterized by XRD, BET, TEM, EDS, TG, SEM and TPR. Catalytic activity of Ni/La2O3-ZrO2 was evaluated by steam reforming of acetic acid at the temperature range of 550-750 °C. The tetragonal phase La0.1Zr0.9O1.95 is formed through the doping of La2O3 into the ZrO2 lattice and nickel species are highly dispersed on the support with high specific surface area. H2 yield and CO2 yield of Ni/La2O3-ZrO2 catalyst with 15%wt Ni reaches 89.27% and 80.41% at 600 °C, respectively, which is attributed to high BET surface area and sufficient Ni active sites in strong interaction with the support. 15%wt Ni supported on La2O3-ZrO2 catalyst maintains relatively stable catalytic activities for a period of 20 h.

Experimental and computational (DFT) approaches were carried out to investigate oxygen vacancies on cerium dioxide. Computational result indicates oxygen vacancies can shorten the band gap of CeO2 and enhance the absorption for visible light because Ce (III) created by generation of oxygen vacancies is easier for excitation than Ce (IV) under same irradiation. The order of calculated band gap for Ce16O31, (111)

This work contributes to a new protocol of patterning gold nanoparticles (NPs) via secondary phase-separation of micelle template of PS- b -P2VP- b -PEO block copolymer. The immiscibility between hydrophobic PS and hydrophilic P2VP and PEO leads to a bulk phase-separation in large compound micelles (LCMs) when heated at the temperature of 130 °C. The bulk-separated template then constitutes an ideal precursor for Au NPs loading by an immersion in an aqueous solution bath of chloroauric acid such that the primed P2VP domains would coordinate to the charged [AuCl 4 ] − through electrostatic interactions. With the following treatment of air plasma, pseudo-hexagonal nanopatterns are created with Au NPs on P2VP matrix.

For a typical Proton exchange membrane (PEM) water electrolysis system, reducing the amount of Ir loading at the anode in membrane electrode assembly (MEA), while maintaining the performance, is still a big challenge. Here, to improve the performance of catalyst layer for oxygen evolution reaction (OER) in an acidic medium, vertical aligned IrOx nanoarrays (IrOx NAs) were synthesized by electrodeposition with TiO2 nanotube arrays (TNTA) as template. By tuning the scan rate in the electrodeposition process, IrOx open-end nanotube arrays with tunable length ranged from 500 nm to 1400 nm and hollow nanorod arrays were obtained due to a diffusion-controlled deposition process. By constructing 3-D electrode of 1-D catalyst with enhanced ion transfer, IrOx NAs performed almost the same current density of OER with 1/20 Ir loading amount compared with commercial IrO2 nanoparticles, which could significantly reduce the cost of catalyst in PEM water electrolyser. Moreover, no apparent current decrease was observed even after 10 h’ anodic polarization under 1.55 V, which exhibit excellent OER durability.

Yolk–shell structure is considered to be a well-designed structure of silicon-based anode. However, there is only one point (point-to-point contact) in the contact region between the silicon core and the shell in this structure, which severely limits the ion transport ability of the electrode. In order to solve this problem, it is important that the core and shell of the core–shell structure are closely linked (face-to-face contact), which ensures good ion diffusion ability. Herein, a double core–shell nanostructure (Si@C@SiO2) was designed for the first time to improve the cycling performance of the electrode by utilising the unique advantages of the SiO2 layer and the closely contacted carbon layer. The improved cycling performance was evidenced by comparing the cycling properties of similar yolk–shell structures (Si@void@SiO2) with equal size of the intermediate shell. Based on the comparison and analysis of the experimental data, Si@C@SiO2 had more stable cycling performance and exceeded that of Si@void@SiO2 after the 276th cycle. More interestingly, the electron/ion transport ability of electrode was further improved by combination of Si@C@SiO2 with reduced graphene oxide (RGO). Clearly, at a current density of 500 mA g−1, the reversible capacity was 753.8 mA h g−1 after 500 cycles, which was 91% of the specific capacity of the first cycle at this current density.

Efficient elimination of tar is a challenge to the development of biomass gasification as a viable clean energy technology. Catalytic reforming is effective in reducing biomass-derived tars. However, commercial metal-based catalysts are expensive and prone to deactivation. Developing economically viable and environmentally benign catalysts from renewable materials is therefore very attractive. This study focuses on the development of an effective tar elimination process utilizing alternative catalysts derived from bauxite residue, a solid waste material from the alumina production. In this work, the catalytic performance of reduced and activated bauxite residue in facilitating naphthalene (a model biomass tar compound) decomposition was studied in a fixed-bed reactor under cracking and reforming environments. Bauxite residue catalyst in reduced form was found to be active for naphthalene reforming, mainly due to its high metallic iron content. However, under wet syngas environments, bauxite residue catalyst was easily deactivated by steam. To address the steam deactivation of bauxite residue catalyst, biochar as a reducing agent, as well as a co-catalyst and adsorptive-support, was proposed to mix with bauxite residue. In this study, biochar from biomass gasification has been successfully employed as a reducing agent to reduce iron oxides in bauxite residue to metallic iron in an inert environment. Results from catalyst activity testing showed that the bauxite residue-biochar mixed catalyst led to highly effective and sustained naphthalene conversion in a reforming environment, since the iron content in bauxite residue was maintained in its reduced form in the presence of biochar.