Bare SiC Research Articles

Biotemplated silicon carbide-loaded ytterbium oxide: Effective catalyst for photocatalytic hydrogen evolution reactions

SiC-doped Yb2O3 structure (Yb2O3/SiC) was prepared to enhance the photocatalytic hydrogen evolution performance of Yb2O3 nanofiber, which have been performed by using catalyst in the presence of eosin-Y dye and triethanolamine, called photosensitizer and electron donor, respectively under solar light with/out cellulose and chitosan. In this study, cellulose and chitosan were used as biotemplates to increase the hydrogen production of Yb2O3/SiC nanofibrous catalyst in the photocatalytic hydrogen evolution reaction. Bioorganic-inorganic structures, cellulose-Yb2O3/SiC and chitosan-Yb2O3/SiC, were obtained by simply adding cellulose and chitosan to the reaction cell without any additional treatment. Cellulose and chitosan also used as a mediator for dispersion, hydrophilicity, morphological transformation and adhesion to semiconductor with the help of functional groups. The hydrogen production rate of bare SiC, bare Yb2O3, Yb2O3/SiC composite have been measured as 391 μmol g−1, 818 μmol g−1 and 1685 μmol g−1, respectively. Moreover, the hydrogen production rate of cellulose-Yb2O3/SiC and chitosan-Yb2O3/SiC composites were came up to 3346 μmol g−1, 4084 μmol g−1, respectively. These results have been showed that the Yb2O3/SiC nanofibrous catalyst showed higher activity in the presence of cellulose and chitosan. The existence of biopolymers will create a new field in photocatalytic hydrogen production studies with the advantages mentioned above, thanks to the functional groups.

Impact of metastable graphene-diamond coatings on the fracture toughness of silicon carbide.

Silicon carbide has excellent mechanical properties such as high hardness and strength, but its applications for body armor and protective coating solutions are limited by its poor toughness. It has been demonstrated that epitaxial graphene-coated SiC can enhance SiC mechanical properties due to the pressure-activated phase transition into a sp3 diamond structure. Here, we show that atomically thin graphene coatings increase the hardness of SiC even for indentation depths of ∼10 μm. Very importantly, the graphene coating also causes an increase of the fracture toughness by 11% compared to bare SiC, which is in contradiction with the general indirect variation of hardness and fracture toughness. This is explained in terms of the presence of a diamond phase under the indenter while the rest of the coating remains in the ultra-tough graphene phase. This study opens new venues for understanding hardness and toughness in metastable systems and for the applications of graphene-coatings.

Design and preparation of LiAlSiO4-Al2O3 coating for the oxidation resistance improvement of SiC ceramics

The low coefficient of thermal expansion (CTE) coating was designed for SiC oxidation-resistant applications by using Al2O3 and LiAlSiO4 as positive and negative expansion materials. The CTE value, relative density and flexural strength of LiAlSiO4-Al2O3 coating were characterized. The effect of LiAlSiO4-Al2O3 coating on the oxidation resistance and flexural strength of SiC substrate was systematically studied by cyclic oxidation tests at 1400 °C. Results showed that LiAlSiO4-Al2O3 coating with 20 wt% LiAlSiO4 exhibited optimal properties, featuring the excellent relative density of 93.14 %, appropriate CTE of 5.815 × 10−6 /°C, and high flexural strength of 56.35 MPa. The weight gain of the SiC with LiAlSiO4-Al2O3 coating was 0.49 % after 100 h of oxidation, much lower than 2.25 % of bare SiC substrate, indicating that LiAlSiO4-Al2O3 coating effectively hindered the diffusion of oxygen and improved the oxidation resistance of SiC substrate. Moreover, the dense coating blunted defects on the SiC substrate surface, which maintained the high strength of the coated SiC after long periods of oxidation.

Preparation strategy for low-stress and uniform SiC-on-diamond wafer: A silicon nitride dielectric layer

Reducing the self-heating of SiC- and GaN/SiC-based high-powered devices by integrating diamond films offers promising performance enhancement of these devices. However, such a reduction strategy faces serious problems, such as diamond nucleation on SiC and stress accumulation greater than 10 GPa. In this work, a SiNx dielectric layer (∼50 nm) was coated onto the C polar face of a 4H–SiC wafer using microwave plasma chemical vapor deposition (MPCVD) to improve direct dense diamond nucleation and growth, significantly reduce the stress, and build Si–C(SiC)⋯Si⋯C(diamond) bond bridges. This SiNx thin layer, prepared by activating Si ions under Ar/N plasma during magnetron sputtering, gave rise to local Si3N4 crystal features and a low effective work function (EWF) for promoting surface dipoles with electronegative carbon-containing groups. In the H plasma environment during diamond growth, the local Si3N4 crystal was amorphized, and the N atoms escaped as a result of atomic H and the high temperature. At the same time, C atoms diffused into the SiNx and formed C–Si bonds (49.7% of the total C bonds) by replacing N–Si and Si–Si, thus increasing the direct nucleation density of the diamond grains. The diamond thin film grew rapidly and uniformly, with a grain size of approximately 2 μm in mixed orientation, and the stress of the 2-inch SiC-on-diamond wafer was extremely low (to ∼0.1–0.2 GPa). In comparison, partially connected diamond grains (>10 μm) on the bare SiC in the preferential (110) orientation resulted in a film with twin-grain features and significant stress, which was associated with the hexagonal lattice interface of 4H–SiC. These results are considered the material and surface/interface bases for actively controlling wafer fabrication and enhancing the heat dissipation of SiC and GaN/SiC electronics.

Ballistic resistance of twisted bilayer graphene with interlayer sp3-bonding on SiC substrate

Carbon occurs in various allotropes due to its bonding flexibility, including diamond-like structures formed by tuning the interlayer spacing of twisted bilayer graphene (TBG), which changes moiré pattern and the fraction of sp3-hybridized interlayer-bonded C atoms as well. Molecular dynamics simulation is employed to explore the ballistic performance of TBG with interlayer sp3-bonding on SiC. We find the specific penetration energy Ep* is kept high for diamond-like TBG with a high fraction of sp3 bonds at small twist angles, e.g., Ep* of SiC coated by diamond-like TBG structure (formed at the twist angle and interlayer spacing equaling 0.7° and 1.79 Å, respectively) is increased by 43.89% and 16.62% compared with bare SiC and bilayer-graphene-coated SiC at room temperature. The kinetic energy transferred to diamond-like TBG/SiC target is absorbed by (i) phase transition in the strike area and destruction until local penetration, (ii) folding deformation of diamond-like structure, and (iii) conic deformation of SiC substrate coupled/driven by the rapid propagation of cone wave in hard coating. Our studies uncover the dynamic protective mechanisms of TBG with interlayer sp3-bonding on SiC substrate, and shed light on the design of lightweight structures for coatings.

Cyclic oxidation performances of new environmental barrier coatings of HfO2-SiO2/Yb2Si2O7 coated SiC at 1375 °C and 1475 °C in the air environment

The objective of this work is to study the cyclic oxidation performances of the environmental barrier coatings (EBCs) containing the novel HfO2-SiO2 bond coats in the air environment. Bi-layer HfO2-SiO2/Yb2Si2O7 (50HfO2-50SiO2, 70HfO2-30SiO2 bond coats) and conventional Si/Yb2Si2O7 EBCs were deposited on SiC substrate using atmospheric plasma spray. The effect of the pre-mixing ratios of HfO2/SiO2 on the cyclic oxidation behavior of HfO2-SiO2/Yb2Si2O7 EBCs was examined. The results showed that the higher content of the HfSiO4 formed from the 50HfO2-50SiO2 bond coats, and it remained intact. A thermally grown oxide (TGO) SiO2 layer was formed at the bond coat/SiC interface. The parabolic oxidation rate constant (kp, μm2/h) of the TGO has been reduced 2 orders of magnitude in 50HfO2-50SiO2/Yb2Si2O7 EBCs coated SiC compared to the bare SiC at 1475 °C, indicating that the 50HfO2-50SiO2/Yb2Si2O7 EBCs effectively protected the SiC substrate at 1475 °C.

Native surface oxidation yields SiC-SiO2 core-shell quantum dots with improved quantum efficiency.

Silicon carbide is an important wide-bandgap semiconductor with wide applications in harsh environments and its applications rely on a reliable surface, with dry or wet oxidation to form an insulating layer at temperatures ranging from 850 to 1250 °C. Here, we report that the SiC quantum dots (QDs) with dimensions lying in the strong quantum confinement regime can be naturally oxidized at a much lower temperature of 220 °C to form core/shell and heteroepitaxial SiC/SiO2 QDs with well crystallized silica nanoshells. The surface silica layer enhances the radiative transition rate of the core SiC QD by offering an ideal carrier potential barrier and diminishes the nonradiative transition rate by reducing the surface dangling bonds, and, as a result, the quantum yield is highly improved. The SiC/SiO2 QDs are very stable in air, and they have better biocompatibility for cell-labeling than the bare SiC QDs. These results pave the way for constructing SiC-based nanoscale electronic and photonic devices.

Structured cobalt–manganese oxides on SiC nano-whisker modified SiC foams for catalytic combustion of toluene

This work presents a two-step method for preparing structured Cobalt-Manganese Oxides nano-sheet (CMO) on SiC nano-whisker (SNW) modified SiC foam support (i.e. CMO@SNW@SiC) and its application to catalytic combustion of toluene. Firstly, SiC nano-whiskers were synthesized on the surface of SiC foam via carbothermal reduction to increase the specific surface area of the resulting structured support (SNW@SiC). Then, CMO were grown on SNW@SiC by hydrothermal synthesis. SNW@SiC provide more surface area, and the nano-sized SiO2/SiCxOy layer on the surface of the SNW promotes the redox reaction of the reactants on the surface, thereby ensuring the directional growth of CMO on SNW@SiC. Compared to the bare SiC foam, CMO loading was increased 67.5% on SNW@SiC. Analysis methods such as H2-TPR, O2-TPD and XPS prove that the redox ability of the CMO on SNW is similar to that of the powder CMO. Toluene catalytic combustion was used as a probe reaction to evaluate catalytic activity. The results show that the CMO@SNW@SiC catalyst could lower the light-off temperature compared to the CMO supported on SiC foam catalyst, which was equivalent to the bulk catalyst (CMO-24h). At the same time, in comparison with the bulk CMO catalyst, the CMO@SNW@SiC catalyst possessed a higher geometric external surface area, which promoted complete conversion of toluene at lower temperatures. In addition, the stability test shows that the CMO@SNW@SiC catalyst also had very good thermal stability and hydrothermal stability as well. The work provided not only the highly performed catalytic oxidation catalyst, but also presented a generic strategy for improving the design of structured catalysts.

Pressureless and low-temperature sinter-joining on bare Si, SiC and GaN by a Ag flake paste

In this work, we applied a Ag flake formed paste for sinter-joining on bare Si, SiC, and GaN surfaces. The sintered joints possess a high shear strength of over 40 MPa under a pressureless sintering condition at 250°C. The high bonding strength of the joints is achieved by a tight adhesion between Ag and bare surfaces, which attributed to an excellent sinter-joining ability of the Ag flake. The flakes, acquired by mechanical milling, can be rapidly sintered into a homogenous porous structure at a pleasureless and low-temperature sintering condition due to its dislocation-rich nano grain structure. During sintering, a drastic morphology reconstruction of Ag flake, from a flattened flake to a drop-like particle, can introduce robust interfacial connection structures, which is important for the robust bonding. This Ag flake paste can be regarded as a promising sinter-joining material for the connection of bare surfaces in high-temperature applications.

Steam oxidation of ytterbium disilicate environmental barrier coatings with and without a silicon bond coat

AbstractThe current generation of multilayer Si/Yb2Si2O7 environmental barrier coatings (EBCs) are temperature limited by the melting point of Si, 1414°C. To investigate higher temperature EBCs, the cyclic steam oxidation of EBCs comprised of a single layer of ytterbium disilicate (YbDS) was compared to multilayered Si/YbDS EBCs, both deposited on SiC substrates using atmospheric plasma spray. After 500 1‐h cycles at 1300°C in 90 vol%H2O‐10 vol%air with a gas velocity of 1.5 cm/s, both multilayer Si/YbDS and single layer YbDS grew thinner silica scales than bare SiC, with the single layer YbDS forming the thinnest scale. Both coatings remained fully adherent and showed no signs of delamination. Silica scales formed on the single layer coating were significantly more homogeneous and possessed a markedly lower degree of cracking compared to the multilayered EBC. The single layer EBC also was exposed at 1425°C in steam with a gas velocity of 14 cm/s in an alumina reaction tube. The EBC reduced specimen mass loss compared to bare SiC but formed an extensive 2nd phase aluminosilicate reaction product. A similar reaction product was observed to form on some regions of the bare SiC specimen and appeared to partially inhibit silica volatilization. The 1425°C steam exposures were repeated with a SiC reaction tube and no 2nd phase reaction product was observed to form on the single layer EBC or bare SiC.

0D/2D Heterojunctions of Ti3C2 MXene QDs/SiC as an Efficient and Robust Photocatalyst for Boosting the Visible Photocatalytic NO Pollutant Removal Ability.

In this work, a novel heterojunction catalyst was constructed by introducing Ti3C2 MXene quantum dots (QDs) into SiC. The Ti3C2 MXene QDs/SiC composite showed 74.6% efficiency in NO pollutant removal under visible light irradiation, which is 3.1 and 3.7 times higher than those of the bare Ti3C2 MXene quantum dots and SiC, respectively. The Ti3C2 MXene quantum dots existing in SiC can function as a channel for electron and hole transfer. The enhanced visible light absorption, increased superoxide radical, and strong oxidization ability endow the Ti3C2 MXene QDs/SiC composite with a superior photocatalytic performance for NOx removal. The increased superoxide radical formation and enhanced oxidization ability of Ti3C2 MXene QDs/SiC were demonstrated by theoretical calculations. The robust stability in both photocatalytic performance and crystal structures was revealed in the Ti3C2 MXene QDs/SiC composite using the cycling test, transient photocurrent response, XRD, and TG.

Fast SiC Switching Limits for Pulsed Power Applications

Solid-state semiconductor switches are emerging as an attractive choice for the fast switching of compact, repetitive, and pulsed power systems. In particular, the high voltage and fast switching capabilities of SiC MOSFETs are well suited for many applications when appropriately gated. For instance, the turn-on and turn-off characteristics of such devices are strongly dependent on the gate driving circuitry. Traditional commercial gate drivers, typically utilizing push–pull or totem-pole driving topologies, are often not well suited for fast, high current switching with rise times on the order of 10–20 ns, as the driving performance is highly dependent on the combined RLC characteristics of the driving circuitry and the switching device. The proposed gate drive topology utilizes a current-carrying inductor to rapidly charge theMOSFET gate–source capacitance. A high-voltage inductive kick generates the necessary potential to drive the inductor current into the gate through the parasitic gate impedance. As the energy stored in the drive inductor is continuously variable, it can be adjusted such that the gate voltage settles to a lower value, typically 20 V, after the initial kick to prevent excessive gate–source overvoltage. With an inductive drive current of ~23 A, a peak $\text{d}I/\text{d}t$ of 25 kA $\mu \text{s}^{-1}$ was achieved for the tested bare SiC MOSFET die. Additionally, a peak $\text{d}I/\text{d}t$ of 13 kA $\mu \text{s}^{-1}$ was achieved with the TO-247 packaged device.

Silicon carbide nanowire covered by vertically oriented graphene for enhanced electromagnetic wave absorption performance

Silicon carbide nanowires (SiC NWs) covered by vertically oriented graphene (SiC@graphene) is prepared by a chemical vapor deposition method. As a microwave absorber, SiC@graphene exhibits a minimum reflection loss (RL) of −16.2 dB at the thickness of 2.5 mm with an absorption bandwidth of 2.64 GHz (RL < −10 dB, 9.5–12.14 GHz), superior than that of the bare SiC NWs. The improved absorption performance is mainly originated from the complex conductive network and the numerous interfaces formed by the vertically grown graphene on the SiC NWs, which are beneficial for multiple scattering and absorptions of the incident microwave.

ZO phonon of a buffer layer and Raman mapping of hydrogenated buffer on SiC(0001)

AbstractWe have measured spatial Raman maps of hydrogen intercalated quasi‐free standing monolayer graphene (QFSMLG) on SiC(0001). We compare Raman spectra of QFSMLG with spectra of bare buffer layer, single‐layer graphene, and bare SiC substrate. We also present the evolution of QFSMLG Raman spectra with the temperature and duration of hydrogen intercalation. We present new Raman modes, and, on the basis of polarization resolved measurements, we attribute them to the totally symmetric out‐of‐plane optical phonon (ZO) modes of the buffer layer at the Γ and M points. We show that these modes are eliminated by hydrogen intercalation; thus, they indicate onset of buffer layer decoupling from the SiC substrate. The spatial mapping of Raman scattering reveals details of the optimal hydrogen intercalation at elevated temperatures. Further increase of the intercalation temperature leads to etching of the buffer layer and underlying SiC substrate. Therefore, we show that interplay between temperature and intercalation time is a promising route towards increased graphene grain size with reduced lattice strain.

Silicon Based Anodes and New Electrolytes for Next Generation Lithium-Ion Batteries and Lithium-Sulfur Batteries

State of the art lithium-ion batteries containing a transition metal cathode and a graphite anode have nearly reached their energy density limit. Due to its high theoretical gravimetric capacity (3590 mAh g-1 Li15Si4) and its low working potential, silicon is an attractive candidate to at least partially substitute the graphite anode [1]. Lithium-sulfur batteries are a promising battery system because of the high capacitive sulfur cathode (1672 mAh g-1) and low material costs. But current cells mainly suffer from the instable lithium anode. Lithiated silicon could be a more stable alternative preventing dendrite formation and electrolyte decomposition for that next generation battery cell type [2]. During the lithiation process of silicon a large undesirable volume expansion occurs. This volume change leads to pulverisation of the silicon and a steady reformation of the solid electrolyte interface (SEI). The electrolyte is consumed and the capacity declines rapidly. This is why silicon anodes with high quantities of silicon are hindered so far. To overcome these obstacles nanostructured silicon carbon composite anodes are very promising. The volume change is potentially compensated by the free volume between silicon core and carbon shell and a stable SEI is ensured at the surface of the carbon shell preventing electrolyte consumption during cycling. These void structures are mainly generated using silica templates which deliver a precise control of the void structure, but need to be removed by toxic hydrofluoric acid and laborious washing steps. In this work an easily scalable process without etching treatment is presented. The void structure results from the removal of a sacrificial template layer on the surface of commercially available silicon particles during the carbonization of the silicon carbon composite within a concerted process. For general electrochemical characterization the silicon carbon composite electrodes are galvanostatic cycled vs. metallic lithium in half cells with different electrolyte systems on coin cell as well as on pouch cell level. The silicon carbon composite electrodes reveal a much higher capacity and cycle stability compared to bare silicon nanoparticles and Si-C composites without void structure. High area capacities above 2.5 mAh cm-2 were reached. In sulfur-lithiated-silicon (SLS) full cells the cycle stability with low lithium excess and the enhanced volumetric energy densities using lithiated silicon anodes was analysed. The electrochemical performance of SLS cells with silicon carbon void structures are compared to that with hierarchical columnar silicon anodes, recently introduced by our group [3]. The feasibility of both SLS cell concepts was successfully demonstrated in coin and in pouch cells. A new electrolyte composition is introduced to enhance the cycle life by stabilization of the SEI and prevention of the electrolyte depletion [4]. Finally, prospects, limits and suggestion for further research directions for SLS cells are envisioned, based on the estimation of the expectable energy density. [1] J. K. Lee, C. Oh, N. Kim, J.-Y. Hwang, Y.-K. Sun, J. Mater. Chem. A 2016, DOI: 10.1039/c6ta00265j [2] J. Brückner, S. Thieme, F. Boettger-Hiller, I. Bauer, H. T. Grossmann, P. Strubel, H. Althues, S. Spange, S. Kaskel, Adv. Funct. Mater. 2014, DOI: 10.1002/adfm.201302169 [3] M. Piwko, T. Kuntze, S. Winkler, S. Straach, P. Härtel, H. Althues, S. Kaskel, J. Power Sources 2017 DOI: 10.1016/j.jpowsour.2017.03.080 [4] M. Piwko, S. Thieme, C. Weller, H. Althues, S. Kaskel, J. Power Sources 2017 DOI: 10.1016/j.jpowsour.2017.07.046

Understanding the Mechanism of SiC Plasma-Enhanced Chemical Vapor Deposition (PECVD) and Developing Routes toward SiC Atomic Layer Deposition (ALD) with Density Functional Theory.

Understanding the mechanism of SiC chemical vapor deposition (CVD) is an important step in investigating the routes toward future atomic layer deposition (ALD) of SiC. The energetics of various silicon and carbon precursors reacting with bare and H-terminated 3C-SiC (011) are analyzed using ab initio density functional theory (DFT). Bare SiC is found to be reactive to silicon and carbon precursors, while H-terminated SiC is found to be not reactive with these precursors at 0 K. Furthermore, the reaction pathways of silane plasma fragments SiH3 and SiH2 are calculated along with the energetics for the methane plasma fragments CH3 and CH2. SiH3 and SiH2 fragments follow different mechanisms toward Si growth, of which the SiH3 mechanism is found to be more thermodynamically favorable. Moreover, both of the fragments were found to show selectivity toward the Si-H bond and not C-H bond of the surface. On the basis of this, a selective Si deposition process is suggested for silicon versus carbon-doped silicon oxide surfaces.

Copper–SiC whiskers composites with interface optimized by Ti3SiC2

In the present work, we propose Ti3SiC2 as the interlayer material to improve the interfacial bonding properties of SiC whiskers-reinforced copper matrix composites. For the first time, Ti3SiC2 coating was in situ fabricated on the surface of SiC whiskers in a molten salt bath. Ti3SiC2-coated SiC whiskers- and bare SiC whiskers-reinforced copper matrix composites were fabricated by spark plasma sintering. The influence of the Ti3SiC2 interlayer on the interfacial properties, mechanical properties, and thermal conductivity of the composites was investigated. The results show that the Ti3SiC2 interlayer can largely improve the interfacial bonding properties of the composites. Therefore, the composites reinforced with Ti3SiC2-coated SiC whiskers exhibit much higher tensile strength than the composites reinforced with bare SiC whiskers. The results also show that the Ti3SiC2 interlayer could decrease the thermal conductivity of the composites in certain extent.

Effect of texture evolution on mechanical and damping properties of SiC/ZnAl2O4/Al composite through friction stir processing

In this investigation, special consideration was given to observe the influence of the acquired ultra-fine-grain (UFG) structure through friction stir processing (FSP) on mechanical and damping properties. As the mechanical behaviour of the composites are intensely related to their microstructure. For deeply understanding the possible mechanism and detailed microstructural observations at a longitudinal cross-section of friction stir processed pure aluminium and several composites reinforced with bare SiC, Al2O3 coated SiC and ZnAl2O4 coated SiC were investigated through EBSD analysis. The mechanical as well as thermal cyclic (from −100 to 400C) damping performance of the friction stir processed composites were studied, respectively. Our first principles calculations show that the storage modulus of the resultant composite SiC/ZnAl2O4/Al was enhanced by a factor of ∼1.9 after FSP as compare to parent Al. The ultimate tensile strength (UTS) of the friction stir processed SiC/ZnAl2O4/Al composite was enhanced by a factor of 3.3 and the acquired microhardness was almost doubled as compare to parent FS processed pure aluminium mainly because of significant grain refinement according to Hall–Petch relationship. Finally, improved properties, attributable to stabilization, enhanced distribution of the tailored SiC particles, improved load transferring capacity and better interface bonding between encapsulated reinforcements and matrix of FS processed composites were obtained with potential application in aerospace and automobile industries.

Hierarchical cobalt oxide-functionalized silicon carbide nanowire array for efficient and robust oxygen evolution electro-catalysis

A hierarchical cobalt oxide (Co3O4)-functionalized silicon carbide nanowire (SiC NW) array electrode is synthesized on 4H–SiC(0001) substrates and investigated for use in the oxygen evolution reaction (OER) of water splitting. Ni-catalyzed chemical vapor deposition is employed to obtain vertically-aligned SiC NWs, and electrodeposition is used to functionalize the nanowires with hierarchical Co3O4 nano-clusters and a thin Co3O4 layer on the top side and the side-walls of the NWs, respectively. By using the Co3O4-functionalized SiC NW electrode for OER, the overpotential required to drive an anodic current density (Janodic) of 10 mA cm−2 is 0.22 V, a value much lower than those of Co3O4 nano-clusters (0.42 V), of bare SiC NWs (1.27 V) electrodes and of Pt foil (0.56 V). The overpotential value of 0.22 V is among the most active for the noble metal-free electro-catalytic electrode to produce Janodic of 10 mA cm−2. The deposition of Co3O4 on the SiC NW substrate produces an extremely hydrophilic surface, which improves the charge transfer characteristics at the interface between the electrode and the aqueous electrolyte. Moreover, the vertically-aligned SiC NWs provide a directional charge transport route along the nanowire length, as seen from a lower charge transfer resistance (Rct) in the Co3O4-functionalized SiC NW electrode compared to the Co3O4-functionalized SiC electrode under the same OER operating conditions. Finally, the Co3O4-functionalized SiC NW electrode maintains stable performance in an alkaline electrolyte (i.e., 1 M KOH aqueous solution) during continuous electrolysis testing over 16 h. The outstanding electro-catalytic performance and stability make the Co3O4-functionalized SiC NW electrode a promising noble metal-free electro-catalytic electrode for the OER and other renewable energy applications.

High-efficient photo-electron transport channel in SiC constructed by depositing cocatalysts selectively on specific surface sites for visible-light H2 production

Control cocatalyst location on a metal-free semiconductor to promote surface charge transfer for decreasing the electron-hole recombination is crucial for enhancing solar energy conversion. Based on the findings that some metals have an affinity for bonding with the specific atoms of polar semiconductors at a heterostructure interface, we herein control Pt deposition selectively on the Si sites of a micro-SiC photocatalyst surface via in-situ photo-depositing. The Pt-Si bond forming on the interface constructs an excellent channel, which is responsible for accelerating photo-electron transfer from SiC to Pt and then reducing water under visible-light. The hydrogen production is enhanced by two orders of magnitude higher than that of bare SiC, and 2.5 times higher than that of random-depositing nano-Pt with the same loading amount.