Mechanism of electrocatalytic CO2 reduction reaction by borophene supported bimetallic catalysts.

Bimetal atom catalysts (BACs) hold significant potential for various applications as a result of the synergistic interaction between adjacent metal atoms. This interaction leads to improved catalytic performance, while simultaneously maintaining high atomic efficiency and exceptional selectivity, similar to single atom catalysts (SACs). Bimetallic site catalysts (M2ß12) supported by ß12-borophene were developed as catalysts for electrocatalytic carbon dioxide reduction reaction (CO2RR). The research on density functional theory (DFT) demonstrates that M2ß12 exhibits exceptional stability, conductivity, and catalytic activity. Investigating the most efficient reaction pathway for CO2RR by analyzing the Gibbs free energy (ΔG) during potential determining steps (PDS) and choosing a catalyst with outstanding catalytic performance for CO2RR. The overpotential required for Fe2ß12 and Ag2ß12 to generate CO is merely 0.05 V. This implies that the conversion of CO2 to CO can be accomplished with minimal additional voltage. The overpotential values for Cu2ß12 and Ag2ß12 during the formation of HCOOH were merely 0.001 and 0.07 V, respectively. Furthermore, the Rh2ß12 catalyst exhibits a relatively low overpotential of 0.51 V for CH3OH and 0.65 V for CH4. The Fe2ß12 produces C2H4 through the *CO-*CO pathway, while Ag2ß12 generates CH3CH2OH via the *CO-*CHO coupling pathway, with remarkably low overpotentials of 0.84 and 0.60 V, respectively. The study provides valuable insights for the systematic design and screening of electrocatalysts for CO2RR that exhibit exceptional catalytic performance and selectivity.

Electrocatalysts for Zinc-Air Batteries Featuring Single Molybdenum Atoms in a Nitrogen-Doped Carbon Framework.

Bifunctional catalysts can facilitate two different electrochemical reactions with conflicting characteristics. Here, a highly reversible bifunctional electrocatalyst for rechargeable zinc-air batteries (ZABs) is reported featuring a "core-shell structure" in which N-doped graphene sheets wrap around vanadium molybdenum oxynitride nanoparticles. Single Mo atoms are released from the particle core during synthesis and anchored to electronegative N-dopant species in the graphitic shell. The resultant Mo single-atom catalysts excel as active oxygen evolution reaction (OER) sites in pyrrolic-N and as active oxygen reduction reaction (ORR) sites in pyridinic-N environments. ZABs with such bifunctional and multicomponent single-atom catalysts deliver high power density (≈376.4 mW cm-2 ) and long cycle life of over 630 h, outperforming noble-metal-based benchmarks. Flexible ZABs that can tolerate a wide range of temperatures (-20 to 80 °C) under severe mechanical deformation are also demonstrated.

Hierarchical 3D Oxygenated Cobalt Vanadium Selenide Nanosheets as Advanced Electrode for Flexible Zinc-Cobalt and Zinc-Air Batteries.

Highly flexible quasi solid-state batteries are promising in next-generation energy storage sectors due to their high energy density, power density, and low manufacturing cost. However, poor cycle life seriously limits their application in industrial sectors. Herein, a novel strategy is established to design the oxygenated cobalt vanadium selenide (O-Cox V1- x Se2 ) nanostructures for high-performance quasi solid-state (QSS) zinc-cobalt batteries (ZCBs) and zinc-air batteries (ZABs). Density functional theory (DFT) calculation reveals that the doping effect of Co2+ into O-VSe2 nanostructure could increase the density of states near the edge of the conduction band, demonstrating ultrafast electron transport kinetics. Most interestingly, the optimal O-Co0.33 V0.67 Se2 cathode-based QSS-ZCB exhibits an ultrahigh specific capacity of 422.7 mAh g-1 at a current density of 1 A g-1 , excellent energy density of 186.4 Wh kg-1 , tremendous power density of 5.65 kW kg-1 , and ultralong cycle life (86.9% capacity retention after 3000 cycles). Furthermore, O-Co0.33 V0.67 Se2 air-cathode based QSS-ZAB delivers a peak power density of 162 mW cm-2 and ultralong cycle life over 100 h. These experimental and theoretical studies indicate that the electrochemically induced, cobalt stabilizes the vanadium is essential to boost the energy storage properties and cycle life of both ZCBs and ZABs.

Hierarchical 3D Oxygenated Cobalt Molybdenum Selenide Nanosheets as Robust Trifunctional Catalyst for Water Splitting and Zinc-Air Batteries.

The development of hierarchical nanostructures with highly active and durable multifunctional catalysts has a new significance in the context of new energy technologies of water splitting and metal-air batteries. Herein, a strategy is demonstrated to construct a 3D hierarchical oxygenated cobalt molybdenum selenide (O-Co1- x Mox Se2 ) series with attractive nanoarchitectures, which are fabricated by a simple and cost-effective hydrothermal process followed by an exclusive ion-exchange process. Owing to its highly electroactive sites with numerous nanoporous networks and plentiful oxygen vacancies, the optimal O-Co0.5 Mo0.5 Se2 could catalyze the hydrogen evolution reaction and oxygen evolution reaction effectively with a low overpotential of ≈102 and 189 mV, at a current density of 10 mA cm-2 , respectively, and exceptional durability. Most importantly, the O-Co0.5 Mo0.5 Se2 ||O-Co0.5 Mo0.5 Se2 water splitting device only entails a voltage of ≈1.53 V at a current density of 10 mA cm-2 , which is much better than benchmark Pt/C||RuO2 (≈1.56 V). Furthermore, O-Co0.5 Mo0.5 Se2 air cathode-based zinc-air batteries exhibit an excellent power density of 120.28 mW cm-2 and exceptional cycling stability for 60 h, superior to those of state-of-art Pt/C+RuO2 pair-based zinc-air batteries. The present study provides a strategy to design hierarchical 3D oxygenated bimetallic selenide-based multifunctional catalysts for energy conversion and storage systems.

Hierarchical Manganese-Nickel Sulfide Nanosheet Arrays as an Advanced Electrode for All-Solid-State Asymmetric Supercapacitors.

In this work, hierarchical manganese-nickel sulfide nanosheet arrays (Mn-Ni-S NAs) were designed through a cost-effective hydrothermal method, followed by an ion-exchange technique. Among the various electrode samples prepared, Mn-Ni-S NAs with a Mn/Ni feeding ratio of 1:2 (denoted Mn-Ni-S NAs (1:2)) were found to possess outstanding electrochemical properties, including a superb areal capacity of 0.687 mAh cm-2 (286.3 mAh g-1 specific capacity) and a splendid cycling stability. Furthermore, Mn-Ni-S NAs (1:2) can be coupled with iron oxide embedded in reduced graphene oxides (Fe2O3@rGO) to assemble all-solid-state asymmetric supercapacitor devices. The resultant device demonstrated superior volumetric capacity and a superb energy density of 76.6 W h kg-1 with a prominent cycling stability. The current synthesis protocol provides a meritorious reference for the synthesis of other kinds of transition-metal sulfide electrode materials for energy storage applications.

Hierarchical Flowerlike Highly Synergistic Three-Dimensional Iron Tungsten Oxide Nanostructure-Anchored Nitrogen-Doped Graphene as an Efficient and Durable Electrocatalyst for Oxygen Reduction Reaction.

A unique and novel structural morphology with high specific surface area, highly synergistic, remarkable porous conductive networks with outstanding catalytic performance, and durability of oxygen reduction electrocatalyst are typical promising properties in fuel cell application; however, exploring and interpreting this fundamental topic is still a challenging task in the whole world. Herein, we have demonstrated a simple and inexpensive synthesis strategy to design three-dimensional (3D) iron tungsten oxide nanoflower-anchored nitrogen-doped graphene (3D Fe-WO3 NF/NG) hybrid for a highly efficient synergistic catalyst for oxygen reduction reaction (ORR). The construction of flowerlike Fe-WO3 nanostructures, based on synthesis parameters, and their ORR performances are systematically investigated. Although pristine 3D Fe-WO3 NF or reduced graphene oxides show poor catalytic performance and even their hybrid shows unsatisfactory results, impressively, the excellent ORR activity and its outstanding durability are further improved by N doping, especially due to pyridinic and graphitic nitrogen moieties into a graphene sheet. Remarkably, 3D Fe-WO3 NF/NG hybrid nanoarchitecture reveals an outstanding electrocatalytic performance with a remarkable onset potential value (∼0.98 V), a half-wave potential (∼0.85 V) versus relative hydrogen electrode, significant methanol tolerance, and extraordinary durability of ∼95% current retention, even after 15 000 potential cycles, which is superior to a commercial Pt/C. The exclusive porous architecture, excellent electrical conductivity, and the high synergistic interaction between 3D Fe-WO3 NF and NG sheets are the beneficial phenomena for such admirable catalytic performance. Therefore, this finding endows design of a highly efficient and durable nonprecious metal-based electrocatalyst for high-performance ORR in alkaline media.

Highly Active and Durable Core-Shell fct-PdFe@Pd Nanoparticles Encapsulated NG as an Efficient Catalyst for Oxygen Reduction Reaction.

Development of highly active and durable catalysts for oxygen reduction reaction (ORR) alternative to Pt-based catalyst is an essential topic of interest in the research community but a challenging task. Here, we have developed a new type of face-centered tetragonal (fct) PdFe-alloy nanoparticle-encapsulated Pd (fct-PdFe@Pd) anchored onto nitrogen-doped graphene (NG). This core-shell fct-PdFe@Pd@NG hybrid is fabricated by a facile and cost-effective technique. The effect of temperature on the transformation of face-centered cubic (fcc) to fct structure and their effect on ORR activity are systematically investigated. The core-shell fct-PdFe@Pd@NG hybrid exerts high synergistic interaction between fct-PdFe@Pd NPs and NG shell, beneficial to enhance the catalytic ORR activity and excellent durability. Impressively, core-shell fct-PdFe@Pd@NG hybrid exhibits an excellent catalytic activity for ORR with an onset potential of ∼0.97 V and a half-wave potential of ∼0.83 V versus relative hydrogen electrode, ultrahigh current density, and decent durability after 10 000 potential cycles, which is significantly higher than that of marketable Pt/C catalyst. Furthermore, the core-shell fct-PdFe@Pd@NG hybrid also shows excellent tolerance to methanol, unlike the commercial Pt/C catalyst. Thus, these findings open a new protocol for fabricating another core-shell hybrid by facile and cost-effective techniques, emphasizing great prospect in next-generation energy conversion and storage applications.

Sustainable Synthesis of Co@NC Core Shell Nanostructures from Metal Organic Frameworks via Mechanochemical Coordination Self-Assembly: An Efficient Electrocatalyst for Oxygen Reduction Reaction.

Herein, a new type of cobalt encapsulated nitrogen-doped carbon (Co@NC) nanostructure employing Znx Co1-x (C3 H4 N2 ) metal-organic framework (MOF) as precursor is developed, by a simple, ecofriendly, solvent-free approach that utilizes a mechanochemical coordination self-assembly strategy. Possible evolution of Znx Co1-x (C3 H4 N2 ) MOF structures and their conversion to Co@NC nanostructures is established from an X-ray diffraction technique and transmission electron microscopy analysis, which reveal that MOF-derived Co@NC core-shell nanostructures are well ordered and highly crystalline in nature. Co@NC-MOF core-shell nanostructures show excellent catalytic activity for the oxygen reduction reaction (ORR), with onset potential of 0.97 V and half-wave potential of 0.88 V versus relative hydrogen electrode in alkaline electrolyte, and excellent durability with zero degradation after 5000 potential cycles; whereas under similar experimental conditions, the commonly utilized Pt/C electrocatalyst degrades. The Co@NC-MOF electrocatalyst also shows excellent tolerance to methanol, unlike the Pt/C electrocatalyst. X-ray photoelectron spectroscopy (XPS) analysis shows the presence of ORR active pyridinic-N and graphitic-N species, along with CoNx Cy and CoNx ORR active (M-N-C) sites. Enhanced electron transfer kinetics from nitrogen-doped carbon shell to core Co nanoparticles, the existence of M-N-C active sites, and protective NC shells are responsible for high ORR activity and durability of the Co@NC-MOF electrocatalyst.

High-energy asymmetric supercapacitors based on free-standing hierarchical Co-Mo-S nanosheets with enhanced cycling stability.

Layered transition metal sulfides (TMS) are emerging as advanced materials for energy storage and conversion applications. In this work, we report a facile and cost-effective anion exchange technique to fabricate a layered, multifaceted, free standing, ultra-thin ternary cobalt molybdenum sulfide nanosheet (Co-Mo-S NS) architecture grown on a 3D porous Ni foam substrate. The unique Co-Mo layered double hydroxides are first synthesized as precursors and consequently transformed into ultra-thin Co-Mo-S NS. When employed as an electrode for supercapacitors, the Co-Mo-S NS delivered an ultra-high specific capacitance of 2343 F g-1 at a current density of 1 mA cm-2 with tremendous rate capability and extraordinary cycling performance (96.6% capacitance retention after 20 000 cycles). Furthermore, assembled Co-Mo-S/nitrogen doped graphene nanosheets (NGNS) in an asymmetric supercapacitor (ASC) device delivered an excellent energy density of 89.6 Wh kg-1, an amazing power density of 20.07 kW kg-1, and superior cycling performance (86.8% capacitance retention after 50 000 cycles). Such exceptional electrochemical performance of Co-Mo-S NS is ascribed to the good electrical contact with the 3D Ni foam, ultra-high contact area with the electrolyte, and enhanced architectural softening during the charging/discharging process. It is expected that the fabricated, unique, ultra-thin Co-Mo-S NS have great potential for future energy storage devices.

Porous Hollow-Structured LaNiO3 Stabilized N,S-Codoped Graphene as an Active Electrocatalyst for Oxygen Reduction Reaction.

A nanohybrid based on porous and hollow interior structured LaNiO3 stabilized nitrogen and sulfur codoped graphene (LaNiO3 /N,S-Gr) is successfully synthesized for the first time. Such a nanohybrid as an electrocatalyst shows high catalytic activity for oxygen reduction reaction (ORR) in O2 -saturated 0.1 m KOH media. In addition, it demonstrates a comparable catalytic activity, longer working stability, and much better alcohol tolerance compared with commercial Pt/C behavior in same experiment condition. The obtained results are attributed to synergistic effects from the enhanced electrocatalytic active sites on the rich pore channels of porous hollow-structured LaNiO3 spheres and heteroatom doped efficiency on graphene structure. In addition, N,S-Gr can meritoriously stabilize monodispersion of the LaNiO3 spheres, and act as medium bridging for high electrical conductivity, thereby providing large active surface area for O2 adsorption, accelerating reduction reaction, and improving electrochemical stability. Such a hybrid opens an interesting class of highly efficient non-Pt catalysts for ORR in alkaline media.

Hierarchical 3D Cobalt-Doped Fe3 O4 Nanospheres@NG Hybrid as an Advanced Anode Material for High-Performance Asymmetric Supercapacitors.

Hierarchical nanostructure, high electrical conductivity, extraordinary specific surface area, and unique porous architecture are essential properties in energy storage and conversion studies. A new type of hierarchical 3D cobalt encapsulated Fe3 O4 nanosphere is successfully developed on N-graphene sheet (Co-Fe3 O4 NS@NG) hybrid with unique nanostructure by simple, scalable, and efficient solvothermal technique. When applied as an electrode material for supercapacitors, hierarchical Co-Fe3 O4 NS@NG hybrid shows an ultrahigh specific capacitance (775 F g-1 at a current density of 1 A g-1 ) with exceptional rate capability (475 F g-1 at current density of 50 A g-1 ), and admirable cycling performance (97.1% capacitance retention after 10 000 cycles). Furthermore, the fabricated Co-Fe3 O4 NS@NG//CoMnO3 @NG asymmetric supercapacitor (ASC) device exhibits a high energy density of 89.1 Wh kg-1 at power density of 0.901 kW kg-1 , and outstanding cycling performance (89.3% capacitance retention after 10 000 cycles). Such eminent electrochemical properties of the Co-Fe3 O4 NS@NG are due to the high electrical conductivity, ultrahigh surface area, and unique porous architecture. This research first proposes hierarchical Co-Fe3 O4 NS@NG hybrid as an ultrafast charge-discharge anode material for the ASC device, that holds great potential for the development of high-performance energy storage devices.

A novel sensitive sensor for serotonin based on high-quality of AuAg nanoalloy encapsulated graphene electrocatalyst.

A high quality graphene-encapsulated AuAg alloy (AuAg-GR) nanohybrid with homogeneous structure and good reproducibility over a desired area was successfully fabricated. Taking benefits of the unique architecture, such nanohybrid was employed as an efficient electrocatalyst for sensing application. The AuAg-GR based sensor could sensitively detected neurotransmitter serotonin (5-HT) with wide linear detection range (2.7nM to 4.82µM), very low detection limit (1.6nM), negligible interference, and excellent reproducibility. In addition, AuAg-GR based sensor accurately determined 5-HT in human serum samples. This is due to the enhanced catalytic activity of GR nanosheets-encapsulated AuAg nanostructures, which possessed well monodispersion of AuAg alloy, greater electrochemical active sites, and good charge transfer possibility. The obtained results imply that such nanohybrid is a potential candidate for synthesizing electrochemical sensors in requirement of high sensitivity, long-term stability, and good reproducibility.

Enhanced Electrochemical and Photocatalytic Performance of Core-Shell CuS@Carbon Quantum Dots@Carbon Hollow Nanospheres.

A controlled structural morphology, high specific surface area, large void space, and excellent biocompatibility are typical favorable properties in electrochemical energy storage and photocatalytic studies; however, a complete understanding about this essential topic still remains a great challenge. Herein, we have developed a new type of functionalized carbon hollow-structured nanospheres based on core-shell copper sulfide@carbon quantum dots (CQDs)@carbon hollow nanosphere (CHNS) architecture. This CuS@CQDs@C HNS is accomplished by a simple, scalable, in situ single-step hydrothermal method to produce the material that can be employed as an electrode for electrochemical energy storage and photocatalytic applications. Impressively, the CuS@CQDs@C HNS nanostructure delivers exceptional electrochemical energy storage characteristics with high specific capacitance (618 F g-1 at a current density of 1 A g-1) and an excellent rate capability with an extraordinary capacitance (462 F g-1 at current density of 20 A g-1) and long cycle life (95% capacitance retention after 4000 cycles). Further, the proposed photocatalyst exhibited superior photocatalytic activity under solar light due to the efficient electron transfer, which was revealed by photoluminescence studies. Such superior electrochemical and photocatalytic performance can be ascribed to the mutual contribution of CuS, CQDs, and CHNS and unique core-shell architecture. These results exhibit that the core-shell CuS@CQDs@C HNS nanostructure is one of the potential candidates for supercapacitors and photocatalytic applications.

A novel hierarchical 3D N-Co-CNT@NG nanocomposite electrode for non-enzymatic glucose and hydrogen peroxide sensing applications.

A novel 3D nanocomposite of nitrogen doped Co-CNTs over graphene sheets (3D N-Co-CNT@NG) have been successfully fabricated via a simple, scalable and one-step thermal decomposition method. This 3D hierarchical nanostructure provides an admirable conductive network for effective charge transfer and avoids the agglomeration of NG matrices, which examine direct as well as non-enzymatic responses to glucose oxidation and H2O2 reduction at a low potential. The novel electrode showed excellent electrochemical performance towards glucose oxidation, with high sensitivity of 9.05µAcm-2mM-1, a wide linear range from 0.025 to 10.83mM, and a detection limit of 100nM with a fast response time of less than 3s. Furthermore, non-enzymatic H2O2 sensors based on the 3D N-Co-CNT@NG electrode exhibited high sensitivity (28.66µAmM-1cm-2), wide linear range (2.0-7449µM), low detection limit of 2.0µM (S/N=3), excellent selectivity, decent reproducibility and long term stability. Such outstanding electrochemical performance can be endorsed to the large electroactive surface area, unique porous architecture, highly conductive networks, and synergistic interaction between N-Co-CNTs and nitrogen doped graphene (NG) in the novel 3D nanocomposite. This facile, cost-effective, sensitive, and selective glucose as well as H2O2 sensors are also proven to be appropriate for the detection of glucose as well as H2O2 in human serum.

Enhanced electrocatalytic performance of an ultrafine AuPt nanoalloy framework embedded in graphene towards epinephrine sensing.

A novel hierarchical nanoporous thin film of AuPt alloy embedded in graphene (AuPt@GR) was successfully synthesized through the self-assembly of ultrafine AuPt nanoparticles (~3nm) within GR sheets by means of a facile chemical vapor deposition (CVD) procedure without the use of any external organic capping agent and reducing agent. A binder-free sensor based on the AuPt@GR hybrid material was fabricated and its electrocatalytic activity was evaluated by using it to determine epinephrine (EP) in PBS solution (pH=7.4) and in human serum spiked PBS solution. Amperometric measurements of the sensor response showed an extremely low limit of detection (0.9nM at a signal-to-noise ratio of 3), high sensitivity (1628µAmM-1cm-2), wide linear detection range (1.5×10-9-9.6×10-6M), and negligible response to interferents. At the same time, the sensor also exhibited very long-term amperometric stability (4000s), cyclic voltammetric stability (500 cycles), good reproducibility, and highly accurate detection of EP in real samples. The excellent electrochemical performance was attributed to synergistic effects of Au, Pt, and GR as well as to the formation of a unique nanoporous structure that provided enhanced electrocatalytic activity, a highly electroactive surface, and fast mass transport. These results suggest strong potential of the AuPt@GR hybrids for use in biosensors and bioelectronic devices.

Novel porous gold-palladium nanoalloy network-supported graphene as an advanced catalyst for non-enzymatic hydrogen peroxide sensing.

In an effort to develop electrocatalysts associated with effective design, testing, and fabrication, novel porous gold-palladium nanoalloy network-supported graphene (AuPd@GR) nanohybrids were successfully synthesized via electroless deposition followed by a chemical vapor deposition (CVD) method for the first time. The AuPd@GR nanohybrids were obtained as a continuous, porous, transparent, bendable, and ultrathin film with good assembly of the AuPd nanoalloy particles (<10nm) within the GR. The AuPd@GR nanohybrids exhibited excellent catalytic activity towards H2O2 detection with a wide detection range (5µM-11.5mM), high sensitivity (186.86µAmM(-1)cm(-2)), low limit of detection (1µM), fast response (3s), and long-term working stability (2500s). Furthermore, the AuPd@GR nanohybrids demonstrated outstanding durability, along with negligible interference from ascorbic acid, dopamine, uric acid, urea, potassium ions, chloride ions, and glucose. These findings open a new pathway to fabricate electrocatalysts for application in high performance electrochemical sensors and bioelectronics.

Facile fabrication of FeN nanoparticles/nitrogen-doped graphene core-shell hybrid and its use as a platform for NADH detection in human blood serum.

Herein, we present a novel strategy for the synthesis of an iron nitride nanoparticles-encapsulated nitrogen-doped graphene (FeN NPs/NG) core-shell hierarchical nanostructure to boost the electrochemical performance in a highly sensitive, selective, reproducible, and stable sensing platform for nicotinamide adenine dinucleotide (NADH). This core-shell hierarchical nanostructure provides an excellent conductive network for effective charge transfer and avoids the agglomeration and restacking of NG sheets, which provides better access to the electrode material for NADH oxidation. The FeN NPs/NG core-shell hierarchical nanostructure demonstrates direct and mediatorless responses to NADH oxidation at a low potential. This material displays a high sensitivity of 0.028µA/µMcm(2), a wide linear range from 0.4 to 718µM, and a detection limit of 25nM with a fast response time of less than 3s. The interferences from common interferents, such as glucose, uric acid, dopamine, and ascorbic acid, are negligible. The fabricated sensor was further tested for the determination of NADH in human blood serum. The resulting high sensitivity, excellent selectivity, outstanding stability, and good reproducibility make the proposed FeN NPs/NG core-shell hierarchical nanostructure as a promising candidate for biomedical applications.

Effective seed-assisted synthesis of gold nanoparticles anchored nitrogen-doped graphene for electrochemical detection of glucose and dopamine.

A novel gold nanoparticle-anchored nitrogen-doped graphene (AuNP/NG) nanohybrid was synthesized through a seed-assisted growth method, as an effective electrocatalyst for glucose and dopamine detection. The AuNP/NG nanohybrids exhibited high sensitivity and selectivity toward glucose and dopamine sensing applications. The as-synthesized nanohybrids exhibited excellent catalytic activity toward glucose, with a linear response throughout the concentration range from 40µM to 16.1mM, a detection limit of 12µM, and a short response time (∼ 10s). It also exhibited an excellent response toward DA, with a wide detection range from 30nM to 48µM, a low detection limit of 10nM, and a short response time (∼ 8s). Furthermore, it also showed long-term stability and high selectivity for the target analytes. These results imply that such nanohybrids show a great potential for electrochemical biosensing application.

Facile synthesis of high quality multi-walled carbon nanotubes on novel 3D KIT-6: application in high performance dye-sensitized solar cells.

A novel hard templating strategy for the synthesis of high quality multi-walled carbon nanotubes (MWCNTs) with a uniform diameter was developed. MWCNTs were successfully synthesized through chemical vapour deposition (CVD) using acetylene by employing 3D bicontinuous mesoporous silica (KIT-6) as a hard template and used as the counter electrode in dye-sensitized solar cells (DSSCs). Here, we report that Ni-Cr-KIT-6 and Co-Cr-KIT-6 systems are the most suitable catalysts for the growth of MWCNTs. Raman spectroscopy and TEM analysis revealed that the synthesized MWCNTs were of high quality and well graphitized. Impressively, DSSCs with a MWCNT counter electrode demonstrated high power conversion efficiencies (PCEs) of up to 10.53%, which was significantly higher than that of 9.87% obtained for a DSSC with a conventional Pt counter electrode. Moreover, MWCNTs had a charge transfer resistance (Rct) of only 0.74 Ω cm(2) towards the I3(-)/I(-) electrolyte commonly applied in DSSCs, which is several orders of magnitude lower than that of a typical Pt electrode (2.78 Ω cm(2)). These results indicate that the synthesized MWCNT counter electrodes are versatile candidates that can increase the power conversion efficiency (PCE) of DSSCs.