Ziming He

Architecture Engineering of Hierarchically Porous Chitosan/Vacuum-Stripped Graphene Scaffold as Bioanode for High Performance Microbial Fuel Cell

The bioanode is the defining feature of microbial fuel cell (MFC) technology and often limits its performance. In the current work, we report the engineering of a novel hierarchically porous architecture as an efficient bioanode, consisting of biocompatible chitosan and vacuum-stripped graphene (CHI/VSG). With the hierarchical pores and unique VSG, an optimized bioanode delivered a remarkable maximum power density of 1530 mW m(-2) in a mediator-less MFC, 78 times higher than a carbon cloth anode.

Nanostructure control of graphene-composited TiO2 by a one-step solvothermal approach for high performance dye-sensitized solar cells

We present a one-step solvothermal approach to prepare uniform graphene-TiO(2) nanocomposites with delicately controlled TiO(2) nanostructures, including ultra-small 2 nm nanoparticles, 12 nm nanoparticles and nanorods. Using three composites as photoanode materials, the effect of nanostructure of graphene-composited TiO(2) on the performance of dye-sensitized solar cells was investigated, and results showed that the ultra-small 2 nm TiO(2)-graphene composite based photoanode exhibited the highest power conversion efficiency of 7.25%.

Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances

Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation.

Understanding the photoelectrochemical properties of a reduced graphene oxide–WO3 heterojunction photoanode for efficient solar-light-driven overall water splitting

WO3–reduced graphene oxide (WO3–RGO) heterojunction electrodes were prepared for photoelectrochemical (PEC) overall water splitting. The WO3 photoanode incorporated with RGO showed significantly enhanced PEC properties and, hence, photocatalytic water splitting, compared to the bare WO3 at a bias larger than 0.7 V vs. Ag/AgCl, while a decrease in the PEC properties of WO3–RGO compared to the WO3 electrode was observed at a bias smaller than 0.7 V vs. Ag/AgCl. RGO could play a favorable role in enhancing the electron–hole separation due to the presence of interface states according to the Bardeen model, but it could also provide active sites for the electron–hole recombination. A more positive applied bias is in favor of effective electron–hole separation, by means of quick collection and transport of electrons by RGO. As a result, a higher PEC performance of WO3–RGO can only be realised at a relatively more positive bias. This study gives insights into the complex nature of a RGO–semiconductor heterojunction, and its implications on the overall photoconversion efficiency.

Understanding TiO2 size-dependent electron transport properties of a graphene-TiO2 photoanode in dye-sensitized solar cells using conducting atomic force microscopy

Conducting AFM reveals a continuous conduction network of a TiO2 -graphene composite in DSSC due to a more intimate contact between the smaller sized TiO2 -graphene composite nanosheets,which reduces the internal resistance at TiO2 /TiO2 and TiO2 /FTO interfaces and ultimately leads to a faster and more efficient electron transport in the photoanode.

A one-pot solvothermal synthesis of hierarchical microspheres with radially assembled single-crystalline TiO2-nanorods for high performance dye-sensitized solar cells

A simple one-pot method to prepare complex morphology-tunable hierarchical TiO2 microspheres consisting of radially assembled single-crystalline rutile TiO2 nanorods is developed by combining an acid thermal crystallization process and a self-assembly process of the nanorods via a solvothermal amphiphile–water microreactor strategy. Using P25 nanoparticles as void fillers to generate a mesoporous electrode film, the microsphere based photoanode exhibits a maximum power conversion efficiency of 7.95% at an anode film thickness of 27.2 μm, highlighting the importance of material architecture tailoring in improving the electron transport properties of dye-sensitized solar cells.

A metal-catalyst free, flexible and free-standing chitosan/vacuum-stripped graphene/polypyrrole three dimensional electrode interface for high performance dopamine sensing

A three dimensional chitosan/vacuum-stripped graphene/polypyrrole interface with a hierarchical porous structure was fabricated as a free-standing and flexible electrochemical sensing electrode for dopamine detection, which exhibits unprecedented good selectivity, high sensitivity (632.1 μA mM-1 cm-2), wide linear response range (0.1-200 μM), low detection limit (19.4 nM, S/N = 3) and good sensing performance in human serum samples, outperforming the previously reported 2D and 3D graphene and/or the PPy modified electrode, and exhibiting comparable performance with the Au modified electrode.

A new strategy for achieving vertically-erected and hierarchical TiO2 nanosheets array/carbon cloth as a binder-free electrode for protein impregnation, direct electrochemistry and mediator-free glucose sensing

We present a new approach to directly grow uniform and highly-ordered TiO2 nanosheets array (NSA) on a low-cost flexible carbon cloth substrate while simultaneously fulfill precise TiO2 nanostructure tailoring and crystal phase control. The unique vertically-erected TiO2 NSA/carbon cloth with hierarchical structures was directly explored as electrode for enzyme immobilization and biosensing applications without suffering any influences of insulating binders usually used to fix nanomaterials on conductive substrates during sensor fabrications. Efficient direct electron transfer was successfully achieved for glucose oxidase (GOx) immobilized on the TiO2 NSA/carbon cloth, which produces a stable, mediator-free glucose sensor with good selectivity, high-sensitivity (52 μA mM(-1)cm(-2)), low response time (<5s) and low detection limit (23.4 μM, S/N=3). The mechanism of the superior direct electrochemical properties and sensing performance was investigated in detail, and discussed from the aspects of material nanostructure and crystalline form of TiO2 NSA, and an intimate contact between TiO2 and carbon cloth resulted from direct crystallization and growth of TiO2 nanosheets on the substrate.

Enhanced charge extraction of polymer solar cell by solution-processable gold nanoparticles

The utilization of metallic nanoparticles is one of the key strategies to improve the performance of photovoltaic devices. In this work, we elucidate the power conversion efficiency (PCE) enhancement mechanism by gold nanoparticles (Au-NPs) through a bilayer anodic buffer structure in polymer solar cells. The results show that the PCE of the device based on a Au-NP:poly(sodium-4-styrenesulfonate)/V2O5 bilayer buffer exhibits a ∼16% enhancement compared with the device without Au-NP. By controlling the density of Au-NPs to minimize plasmonic effects, the Au-NP induced enhancement of charge extraction and crystallinity of the photoactive layer were demonstrated for the first time. Our work indicates that the plasmonic effect may not be the only factor that enhances the PCE of polymer solar cells, while providing new insights into the roles of Au-NPs in performance improvement of a bulk-heterojunction polymer solar cell.

Electropolymerization of Uniform Polyaniline Nanorod Arrays on Conducting Oxides as Counter Electrodes in Dye-Sensitized Solar Cells.

Conventional techniques for the synthesis of oriented polyaniline (PANI) nanostructures are often complex or time consuming. Through an innovative reduced graphene oxide (rGO) modified FTO and a low-potential electropolymerization strategy, the rapid and template-free growth of a highly ordered PANI nanorod array on the FTO substrate is realized. The highly ordered nanostructure of the PANI array leads to a high electrocatalytic activity and chemical stability. The importance of the polymerization potential and rGO surface modification to achieve this nanostructure is revealed. Compared to platinum, the PANI nanorod array exhibits an enhanced performance and stability as counter electrodes in dye-sensitized solar cells, with a 17.6 % enhancement in power conversion efficiency.