Wenyu Gao

A novel Ni3N/graphene nanocomposite as supercapacitor electrode material with high capacitance and energy density

A novel Ni3N/graphene nanocomposite of small Ni3N nanoparticles anchoring on the reduced graphene oxide nanosheets has been successfully synthesized. Due to the quite small size of Ni3N nanocrystals, the surface for faradic redox reaction of pseudocapacitive materials dramatically increases. The main issue of the volume change obstructing the pseudo-supercapacitor performance is concurrently resolved by the tight attachment of Ni3N nanoparticles with flexible texture. Importantly, the two-step oxidation/reduction reaction between Ni(I) and Ni(III) endows this nanocomposite with large capacitance by providing more faradic charge. The kind of electrode material behaves excellently both in three-electrode and asymmetric supercapacitors. The biggest specific capacitance reaches to 2087.5 F g(-1) (at 1 A g(-1)), and its asymmetric supercapacitor cell with ethylene glycol modified RGO as negative electrode has a high energy density (50.5 W h kg(-1) at 800 W kg(-1)). The cell capacitance retention exceeds 80% after 5000 cycles at different high current densities, showing its promising prospects for high-energy supercapacitors.

Highly sensitive nonenzymatic glucose sensor based on nickel nanoparticle–attapulgite-reduced graphene oxide-modified glassy carbon electrode

In this article, a fast and sensitive nonenzymatic glucose sensor is reported utilizing a glassy carbon electrode modified by synthesizing nanocomposites of nickel nanoparticle-attapulgite-reduced graphene oxide (Ni NPs/ATP/RGO). A facile one-step electrochemical co-deposition approach is adopted to synthesize Ni NPs-ATP-RGO nanocomposites via electrochemical reduction of mixed precursor solution containing graphene oxide (GO), attapulgite (ATP) and nickel cations (Ni(2+)) at the cathode potentials. This strategy results in simultaneous depositions of ATP, cathodic reduction of Ni(2+) into nickel nanoparticles under acidic conditions, and in situ reduction of GO. The as-prepared NiNPs/ATP/RGO-based glucose sensor exhibits outstanding performance for enzymeless glucose sensing with sensitivity (1414.4 μAmM(-1)cm(-2)), linear range (1-710μM) and detection limit (0.37μM). What is more, the sensor has excellent stability and selectivity against common interferences in real sample.

An electrochemical DNA sensor based on polyaniline/graphene: high sensitivity to DNA sequences in a wide range

A label-free electrochemical DNA sensor was fabricated by deposition of polyaniline and pristine graphene nanosheet (P/G(ratios)) composites in different mass ratios, DNA probe and bovine serum albumin (BSA) layer by layer on the surface of a glassy carbon electrode (GCE). Electrochemical impedance spectroscopy (EIS) was employed to monitor every step of fabrication of P/G(ratio)-based DNA sensors and to evaluate the detection results in terms of the hybridization of complementary DNA, mutant DNA and non-complementary DNA. The results illustrate that the P/G(ratio)-based DNA sensor could highly efficiently detect complementary DNA from 0.01 pm to 1 μm and discriminate single-nucleotide polymorphisms (SNPs). In the process of detection, double-stranded DNA (dsDNA), resulting from hybridization of a DNA probe, escaping from or remaining on the sensor surface, was monitored by changing the ratio of polyaniline (PANI) to graphene, which was decided by the competition between the electrostatic interaction and Brownian motion.

Aromatic ring substituted g-C3N4 for enhanced photocatalytic hydrogen evolution

A facile strategy to fabricate modified g-C3N4 with all-carbon aromatic rings incorporated in the constitutive plane was presented. The light absorption, band structure and photo-induced carrier separation of this benzene doped g-C3N4 was extremely improved. It exhibited a 3 times higher hydrogen evolution rate (HER) and a 17 times higher HER per surface area.

Surface Engineering for Extremely Enhanced Charge Separation and Photocatalytic Hydrogen Evolution on g‐C3N4

Reinforcing the carrier separation is the key issue to maximize the photocatalytic hydrogen evolution (PHE) efficiency of graphitic carbon nitride (g-C3 N4 ). By a surface engineering of gradual doping of graphited carbon rings within g-C3 N4 , suitable energy band structures and built-in electric fields are established. Photoinduced electrons and holes are impelled into diverse directions, leading to a 21-fold improvement in the PHE rate.

Trivalent cerium-preponderant CeO2/graphene sandwich-structured nanocomposite with greatly enhanced catalytic activity for the oxygen reduction reaction

A sandwich-like CeO2/graphene nanocomposite (CeGS) with a uniform thin CeO2 crystalline film coating on reduced graphene oxide is presented. Large amounts of trivalent Ce and abundant oxygen vacancies (VO) were introduced onto the surface of CeGS. Due to the advantageous surficial crystal configuration, this CeGS displayed greatly enhanced catalytic activity and excellent durability for the oxygen reduction reaction (ORR). By DFT calculations, it was demonstrated that the Ce(III)-preponderant and VO-containing surface benefited the intense chemical adsorption and activation of O2 and optimized the intermediate reaction pathways.

Highly sensitive and selective detection of cadmium with a graphite carbon nitride nanosheets/Nafion electrode

A highly sensitive and selective electrochemical sensor is developed for the detection of cadmium with a nanosheet graphitic carbon nitride (g-C3N4) modified electrode. The g-C3N4 nanosheet modified glassy carbon electrode detects heavy metal not only by electrostatic interactions, but also by intercalating the holes during differential pulse anodic stripping voltammetry (DPASV) measurements for Cd2+ in aqueous solution. The calibration curves for Cd2+ covered two ranges varying from 1 nM to 1 μM and 1 μM to 100 μM. The limitation of detection (LOD) is estimated to be 0.5 nM for Cd2+, which is 53 times lower than the guideline values of drinking water given by the World Health Organization (WHO). In addition, the good repeatability and stability of the modified electrode is feasible for heavy metal detection in this study.