Construction Of Pt-modified Electrodes Via Novel Protocols For Electrocatalysis And Biosensing Applications

Study on the electrocatalytic oxidation of small organic molecules (methanol, formaldehyde and formic acid) is of great importance for exploitation and development of direct fuel cells. The preparation of nanomaterials is not only beneficial to electrocatalytic oxidation of small organic molecules, but also to construction of more sensitive biosensing interfaces. Herein, based on literature survey, the studies in this thesis are summarized as follows:1. Based on Cu underpotential deposition (UPD) can take place similarlyon both Au and Pt surfaces, new dynamic Cu UPD protocol was proposed toconstruct Pt_UPD/Au electrodes, with in situ electrochemical quartz crystalmicrobalance (EQCM) monitoring of the fabrication processes. Theelectrocatalytic activity of Pt_UPD/Au electrodes toward methanolelectrooxidation was studied, in comparison with that prepared viaconventional monocomponent elctrodeposition protocol from chloroplatiniicacid (Pt_con/Au). The Pt_UPD/Au showed higher electrocatalytic activity thanPt_con/Au. At a Pt load of 16μg cm^-2, the specific electrocatalytic activity(SECA) of Pt_UPD/Au toward methanol electrooxidation was found to be 1.25A cm^-2 mg^-1 in 0.5 mol L^-1 CH₃OH + 0.5 mol L^-1 H₂SO₄and 5.32 A cm^-2 mg^-1in 0.5 mol L^-1 CH₃OH + 1.0 mol L^-1 NaOH media, respectively, being largerthan those for Pt_con/Au (0.31 and 1.32 A cm^-2 mg^-1, respectively). Theelectrodes kinetics studies indicated that methanol electrooxidation reactionwas a diffusion-controlled process, and the activation energy at was lower than that at Pt_con/Au.2. Pt nanoparticles modified glassy carbon (GC) electrodes were fabricated via Pt-Pb coelectrodeposition followed by electrochemical stripping of Pb, and the electrocatalytic oxidation of C1 organic small molecules (methanol, formaldehyde and formic acid) were examined on the prepared Pt modified electrodes. Results showed that the electrocatalytic activity of the Pt modified electrodes prepared via the proposed protocol was about 1.6-fold of those via conventional monocomponent Pt electrodeposition protocol, 40-fold of the bulk Pt disk electrode. Meanwhile, the electrodes prepared via Pt-Pb coelectrodeposition/Pb stripping protocol possessed better stability than those via conventional monocomponent Pt electrodeposition protocol.3. Pt nanoparticles well dispersed on multiwalled carbon nanotubes (MWCNTs) for high-performance electrocatalytic oxidation of methanol in both acidic and alkaline media were prepared via the Pt-Cu coelectrodeposition/Cu stripping (CS) protocol. The SECA of the Pt catalyst prepared by the CS protocol on MWCNTs (Pt_cs/MWCNTs/Au) was found to be 1.79 and 7.62 A cm^-2 mg^-1 toward methanol electrooxidation in 0.5 M CH₃OH + 0.5 M H₂SO₄ and 0.5 M CH₃OH + 1.0 M NaOH media, respectively, which are larger than those prepared by conventional electrodeposition from chloroplatinic acid on Au and MWCNTs/Au (Pt/Au and Pt/MWCNTs/Au), as well as CS protocol on Au (Pt_cs/Au). The Pt_cs/MWCNTs/Au also possessed the highest stability. The electrode kinetics studies showed that the activation energy toward methanol electrooxidation at Pt_cs/MWCNTs/Au is lowest among all the examined cases. Lowest activation energy indicated that nanosubstrate-based CS protocol for nanoelectrocatalysts fabrication is beneficial for direct methanol fuel cells (DMFCs) exploitation and development.4. Hydrogen peroxide and glucose electrochemical biosensor was constructed based on Pt_cs/MWCNTs/GC electrode. Pt_cs/MWCNTs/GC electrode showed good response to hydrogen peroxide with the linear range between 0.05 to 4 mmol L^-1, sensitivity of 2.83 mA cm^-2 mmol L^-1, being larger than MWCNTs/GC and Pt_cs/GC electrode. Nafion/GOx/Pt_cs/MWCNTs/GC electrode showed good response to glucose with the linear range between 0.05 to 6 mmol L^-1, sensitivity of 10.8μA cm^-2 mmol L^-1, being larger than Nafion/GOx/MWCNTs/GC and Nafion/GOx/Pt_cs/GC electrode. The glucose biosensor based on Nafion/GOx/Ptcs/MWCNTs/GC also showed good anti-interferent ability and stability, which is promising for glucose detection in practice.