Xiqing Yuan

A novel hollow sphere bismuth oxide doped mesoporous carbon nanocomposite material derived from sustainable biomass for picomolar electrochemical detection of lead and cadmium

A novel ultrasensitive, selective and low cost electrochemical sensor based on a hollow sphere bismuth oxide doped mesoporous carbon aerogel nanocomposite derived from a sustainable biomass material was successfully fabricated for simultaneous Pb2+ and Cd2+ detection at picomolar levels. In this nanocomposite material, we successfully brought together the advantages of an extraordinarily large surface area biomass derived carbon matrix with mesopores for analyte pre-enrichment and the excellent electroanalytical activity of the bismuth oxide hollow sphere structure for highly sensitive heavy metal sensing. Under optimized conditions, this electrode material exhibited a very low detection limit of 1.72 pM for Pb2+ and 1.58 pM for Cd2+ under ambient conditions, the lowest ever limit of detection recorded for the detection of both Pb2+ and Cd2+ using activated carbon. Furthermore, two wide linear ranges from 0.5 pM to 10 pM and from 10 pM to100 pM were observed due to the differences of adsorption dynamics at different metal ion concentration ranges. The nanocomposite sensor material demonstrated excellent reproducibility and great resistance to interference. Furthermore, the application for real water analysis was demonstrated and the result was highly consistent with the measurement from inductively coupled plasma optical emission spectroscopy (ICP-OES).

Activated microporous-mesoporous carbon derived from chestnut shell as a sustainable anode material for high performance microbial fuel cells

Microbial fuel cells (MFCs) are promising biotechnologies tool to harvest electricity by decomposing organic matter in waste water, and the anode material is a critical factor in determining the performance of MFCs. In this study, chestnut shell is proposed as a novel anode material with mesoporous and microporous structure prepared via a simple carbonization procedure followed by an activation process. The chemical activation process successfully modified the macroporous structure, created more mesoporous and microporous structure and decreased the O-content and pyridinic/pyrrolic N groups on the biomass anode, which were beneficial for improving charge transfer efficiency between the anode surface and microbial biofilm. The MFC with activated biomass anode achieved a maximum power density (23.6 W m-3) 2.3 times higher than carbon cloth anode (10.4 W m-3). This study introduces a promising and feasible strategy for the fabrication of high performance anodes for MFCs derived from cost-effective, sustainable natural materials.

Facile synthesis of mesoporous graphene platelets with in situ nitrogen and sulfur doping for lithium–sulfur batteries

The interaction between lithium polysulfides and doped heteroatoms could prevent the loss of soluble polysulfides in the cathode and mitigate the shuttle effect in lithium–sulfur batteries. Herein, a facile synthesis of mesoporous graphene platelets (NSGs) with in situ nitrogen and sulfur doping by the pyrolysis of a self-assembled L-cysteine precursor on sodium chloride crystal surface for structure-directing is presented. The mesoporous lamellar structure of the NSG possesses a uniform distribution of pyrrolic N, pyridinic N, and thiosulphate structured heteroatoms originating from in situ doping, which promotes the confinement of intermediate polysulfides. Combining the strong interactions with soluble polysulfide, flexible mesoporous architecture, and high conductivity of graphene, the prepared NSG material exhibited a high initial capacity of 1433 mA h g−1 at a 2C rate as well as a reversible capacity of 684 mA h g−1 after 200 cycles. This demonstrates that the in situ nitrogen and sulfur doped thin lamellar structure of graphene would be a promising cathode material for high performance lithium–sulfur batteries.

Lamellar mesoporous carbon derived from bagasse for the cathode materials of lithium–sulfur batteries

Mesoporous lamellar carbon was produced by direct high temperature carbonization of bagasse, a novel process designed with affordable cost and ease of production for scale-up manufacturing. The lamellar carbon exhibited a highly mesoporous structure with favorable pore size distribution, large surface area and good electrical conductivity derived from the intrinsic thin-walled parenchyma cells of bagasse. The produced lithium–sulfur battery exhibited excellent cycle stability, due to the unique pore structure of bagasse that can accommodate the drastic volume change during battery cycling, and good rate performance, due to the high electrical conductivity of bagasse derived carbon after pyrolysis. A high initial reversible capacity of 1202 mA h g−1 (S) at 0.1C as well as a reversible capacity of 494 mA h g−1 (S) after 180 cycles at 1C was achieved, and the capacity retention was also found to be more than 70% at 1C. The designed processing method for the facile production of lamellar mesoporous carbon derived from direct carbonization of bagasse should be a feasible method for the mass production of cathode materials for high performance lithium–sulfur batteries.

The effect of barium sulfate-doped lead oxide as a positive active material on the performance of lead acid batteries

Barium sulfate (BaSO4) is a common impurity in recycled lead paste that is challenging to eliminate completely during hydrometallurgical recycling of spent lead acid batteries, so the effect of this impurity in positive active materials on the performance of recycled lead acid batteries was investigated. The BaSO4 doped lead oxide composite was used as a positive active material in positive plates of lead acid batteries with theoretical capacities of 2.0 A h. BaSO4 was retained in the solid phase throughout the battery fabrication process. Different BaSO4 dosages affected the phase of the positive plates during the curing process, with the highest content of metallic lead obtained at a BaSO4 dosage of 0.06 wt%. Morphology analysis indicated that aggregates were formed in the positive plates and the particles became rougher with increasing addition of BaSO4 during the formation process. BaSO4 also demonstrated a large impact on charge/discharge cycles with 100% DOD in battery testing. Analysis of disassembled failed batteries indicated that the expansion and shedding-off of the positive active material were mainly responsible for the failure of these batteries, and this could be attributed to the non-uniform growth of lead oxide on the BaSO4 nucleus, and the accumulation of internal stress.