脉冲电沉积法制备双贵金属催化剂及其电化学性能研究

目的 制备对偏二甲肼具有良好电催化活性响应的复合催化剂。方法 运用脉冲电沉积法在玻碳电极上制备了AuPd、AuPt、PdPt催化剂，研究了占空比、上下限电位、脉冲频率、沉积时间等条件的影响，采用扫描电镜、X射线衍射仪表征了其表面形貌和晶体结构，采用电化学循环伏安法研究了催化剂氧还原反应(ORR)活性和对偏二甲肼(UDMH)电催化氧化活性。结果 3种催化剂的双金属均已合金化，AuPd催化剂为纳米晶枝状结构，AuPt催化剂为纳米球状结构。当占空比为1∶10，上下限电位分别为0.7、0.3 V，沉积频率为10 Hz，沉积时间为20 min时，AuPd催化剂的ORR活性达到最佳;当占空比为1∶30，上下限电位分别为1.1、‒0.1 V，沉积频率为0.05 Hz时，PdPt催化剂的ORR活性达到最佳;当占空比为1∶10，上下限电位分别为1.3、‒0.2 V，沉积频率为0.5 Hz，沉积时间为10 min时，AuPt催化剂的ORR活性达到最佳。AuPd、AuPt催化剂对UDMH具有明显的电催化响应，AuPd的氧化峰积分高达0.23 mAV/cm²，AuPt高达0.25 mAV/cm²。结论 脉冲电沉积法制备的Au基AuPd、AuPt复合催化剂相较于PdPt催化剂和商业Pt/C催化剂对UDMH有更高的电催化活性。

Preparation of Bimetallic Catalysts by Pulsed Electrodeposition and Its Electrochemical Performance Study

The work aims to prepare composite catalysts with good electrocatalytic activity response to unsymmetrical dimethylhydrazine. The pulsed electrodeposition method was used to prepare AuPd, AuPt and PdPt catalysts on glassy carbon electrodes. The working electrode was a glassy carbon electrode with a diameter of 3 mm. The counter electrode was a platinum wire electrode and the reference electrode was a saturated glycolic electrode (SCE). The effects of duty cycle, upper and lower limit potentials, pulse frequency and deposition time were investigated, and the surface morphology and crystal structure were characterized by scanning electron microscopy and X-ray diffraction. And the catalyst oxygen reduction reaction (ORR) activity and electrocatalytic oxidation activity towards unsymmetrical dimethylhydrazine (UDMH) were investigated by electrochemical cyclic voltammetry. All three catalysts were alloyed. The AuPd catalyst was a unique nanodendritic structure with an Au∶Pd element ratio of 1∶1 and an average particle size of 20 nm. The AuPt catalyst was a unique nanosphere structure with an Au∶Pt element ratio of 2∶3 and an average particle size of 100 nm. The PdPt catalyst was a homogeneous nanoparticle with a Pd:Pt element ratio of 1∶1 and an average particle size of 1.7 nm. The best ORR activity of the AuPd catalysts was achieved when the duty cycle was 1∶10, the upper and lower potentials were 0.7 V and 0.3 V, the deposition frequency was 10 Hz and the deposition time was 20 min; The best ORR activity of the PdPt catalysts was achieved when the duty cycle was 1∶30, the upper and lower potentials were 1.1 V and ‒0.1 V and the deposition frequency was 0.05 Hz; The best ORR activity of AuPt catalyst was achieved when the duty cycle was 1:10, the upper and lower limit potentials were 1.3 V and ‒0.2 V, the deposition frequency was 0.5 Hz and the deposition time was 10 min. It was worth noting that the ORR activity of the PdPt catalyst showed a linear relationship with the deposition time over a range. Previous surface morphology analysis showed that the small and homogeneous particles of the PdPt catalyst were the main reason for the good linear relationship between deposition time and ORR activity. The effective catalytic area of the PdPt catalyst could be precisely controlled by adjusting the deposition time. The CV curve showed that AuPd and AuPt catalysts showed double oxidation peaks similar to methanol oxidation. The UDMH oxidation peaks appeared around 0.7 V for the positive sweep and around 0.3 V for the negative sweep, while the PdPt and Pt/C catalysts had no significant UDMH oxidation peaks at these two locations. The integration of the oxidation peaks from 0.3 V to 0.8 V was calculated to be as high as 0.23 mAV/cm2 for AuPd and 0.25 mAV/cm2 for AuPt. The Au-based AuPd and AuPt composite catalysts prepared by pulsed electrodeposition method show higher electrocatalytic activity to UDMH compared with the PdPt catalysts and commercial Pt/C catalysts. It provides a new idea for the establishment of electrochemical catalytic oxidation based degradation of high concentration UDMH waste streams.