the National Natural Science Foundation of China(21363024);Ph. D. Scientific Initiate Funding Project of XinjiangNormal University, China(XJNUBS1228);Xinjiang Autonomous Region 2013 Annual Colleges and Universities Scientific Research PlanYoung Teacher Cultivation Project, China(XJEDU2013S29)
Chemistry and Chemical Engineering Academy, Xinjiang Normal University, Urumuqi 830054, P. R. China
Abstract:
A nanocomposite composed of N-doped mesoporous carbon material (NDMPC) and carboxymethylated chitosan (CMCH) was fabricated by mechanical co-mixing and used as an enzyme matrix. A novel glucose/O2 enzymatic biofuel cell was fabricated with a Nafion ion-exchange membrane consisting of a laccase (Lac)-entrapped biocathode and glucose oxidase-incorporated bioanode. Enzyme electrodes were prepared by the dripping coat and air-dried method. The performance of the laccase-based electrode as a biocathode in a fuel cell and an oxygen electro-chemical sensor was characterized by cyclic voltammetry in combination with the rotating disk electrode technique, linear scanning voltammetry (LSV), and chronoamperometry. UV-Vis spectrometry and graphite furnace atomic absorption spectroscopy were used to investigate the configuration of enzyme molecules on the surface of electrode and to evaluate the enzyme loading of the matrix on the electrode interface. The results from the experiments showed that the laccasebased cathode displayed direct electron transfer between the active centre in laccase (T1) and the conductive matrix without any external electron mediators (apparent electron transfer rate 0.013 s-1). A minor overpotential for oxygen reduction (150 mV) was also observed. Through further comparison of the intra-molecule electron relay rate (1000 s-1), substrate turnover frequency (0.023 s-1), and previous enzyme-conductive matrix electron transfer rate, quantitative analysis showed that the latter was the rate-determining step in the whole catalytic cycle of the oxygen reduction reaction. This laccase-based electrode as an oxygen electrochemical sensor for detecting oxygen showed a low detection limit (0.04 μmol·dm-3), high sensitivity (12.1 μA·μmol-1·dm3), and affinity for oxygen (KM = 8.2 μmol·dm-3). This laccase-based cathode also had advantages such as excellent reproducibility, long-term usability, thermal stability, and pH endurance. The results for the fabricated biofuel cell showed an open circuit voltage of 0.38 V and a maximal energy output density of 19.2 μW·cm-2, maintaining greater than 60% of the initial value even after continuous work for 3 weeks under optimal conditions.
