Au/Pt纳米柱阵列电极的制备及光电催化氧化甲醇性能

Preparation of Platinum-modified Uniform Gold Nanopillar Electrodes and Photoelectrocatalytic Oxidation of Methanol

利用纳米压印、电沉积和气相沉积方法构筑了有序均一的Au及Au/Pt纳米柱阵列电极.通过反射光谱观测到580和660 nm附近的特征吸收谱峰,并基于有限元电磁场(FEM)理论模拟,确定其表面等离激元共振(SPR)性质分别对应于纳米柱柱顶的电偶极模式(584 nm)、电四极模式(638 nm)以及表面等离激元极化子(666 nm).制备的等离激元纳米柱电极用于甲醇光电催化氧化反应时,SPR效应能显著地增强甲醇的电催化氧化电流.当表面负载2 nm的金属Pt时,光电催化氧化甲醇活性最高,光照使氧化电流增加,同时甲醇的氧化峰电位随光强的增加逐渐负移,证明SPR弛豫产生的热空穴参与到光电协同甲醇氧化中.在恒电流甲醇氧化实验中,光照使表面氧化反应时间延长6倍,减小了CO的毒化,证明SPR对于电极表面产生一定的清洁作用.

Surface plasmons(SPs)excitation in nanostructured noble metals has been shown to effectively ac⁃celerate and drive photochemical reactions.Methanol,as an important alcohol fuel,has the characteristics of high energy density,wide source,low price and convenient storage.It can be used as a raw material in direct methanol fuel cell(DMFC).At present,studies have shown that surface plasmon resonance(SPR)can effec⁃tively enhance the oxidation efficiency of methanol.However,most of the current composite catalysts are coreshell structure nanoparticles,and their stability and repeatability have become a problem to be overcome,es⁃pecially the thickness of the catalytic metal on the surface of the core-shell structure is not uniform and diffi⁃cult to control,which has caused many uncertainties in the study of plasmon-catalyzed methanol oxidation.Therefore,this paper uses thermal lithography and ultraviolet lithography to prepare a hole array on photoresist coated glass electrode substrate with a period of 450 nm.Gold nanopillars were uniformly grown in the elec⁃trode holes with a constant current electrodeposition technique in gold sodium sulfite solution until the holes were completely filled,and a gold nanopillar array structure with a height of about 180 nm and a diameter of about 200 nm was obtained.Combined with gas phase deposition technology,a nano-Au/Pt electrode with or⁃dered structure,uniform hot spots and large-scale production was obtained.With finite element method(FEM)analysis,the visible light absorption peaks of Au/Pt electrodes with different thicknesses and their corresponding electric field modes were simulated,which,combined with experimental results,proved that the elec⁃trodes have three plasmon excitation modes,including SPR at the bottom of the column and the gold film,the surface plasmon polariton(SPP)coupling on the gold film which blue-shifted when the thickness of Pt increases,and the SPR coupling on the top of the nanopillar.Finally,the electrocatalytic performance of this elec⁃trode on methanol oxidation reaction under illuminations was studied,and proved that 2 nm Au/Pt has the best oxidation effect.In the 30 mA constant current oxidation of methanol experiment,light can prolong the lifetime of the electrode about 6 times,and the SPR effects help electrode surface to have a self-cleaning effect.