Preparation And Electrocatalytic Activity Of Dendritic Silver Particles And Their Composites

Preparation of nanometer materials has become an important research fieldbecause of their special physical and chemical properties. At present, different typesof metal-polymer composites have been developed and investigated. The reason isthat they can bring benefits in the basic science and different technology applications.Especially, study on electro-catalytic activity of silver nano-particles is of veryimportant significance both in the theory and in application. Therefore, thepreparation of silver nano materials and their modification present very importantresearch value.Silver nano-particles and their alloys with other metals with differentmorphologies have been prepared by using the method of electro-deposition in thispaper. Effect of deposition conditions on the silver nano-particles has been studiedand the silver catalyst compositions, structures and morphologies have beencharacterized and analyzed. The electro-catalytic activity of the prepared catalysts foroxidation of formaldehyde and glucose, and oxygen reduction in alkaline solution hasbeen studied by using cyclic voltammetry, linear scanning and constant potential step.The main conclusions are as follows:（1） The novel dendrite-like silver nano-particles are prepared by the method ofelectro-deposition. Effect of deposition potential, Ag（NH₃）₂⁺solution concentration,solution temperature, substrate, and alkaline earth metal ions on silver nano-particlesmorphology has been examined intensively.（2） Novel dendrite-like silver nano-particles （Ag/Ti） are deposited on the Tisubstrate in-1.6V（vs Ag） potential. The electro-catalytic activity of the silvernano-particles for formaldehyde oxidation has been investigated. The tests show thatthe formaldehyde detection sensitivity （S） is0.27mA·cm^-2·(mmol·L^-1), and detectionlimit is0.662mmol·L^-1. The results show that the nanometer Ag/Ti catalyst can beused as a formaldehyde electrochemical sensor.（3） By changing the Ag（NH₃）₂⁺concentration in solution and using the method ofelectro-deposition, different shapes of dendrite-like silver nano-particles have been prepared on titanium substrates. Their electro-catalytic activity for glucose oxidationin0.1mol·L^-1NaOH solution has been investigated. The glucose detection sensitivityis0.57mA·cm^-2·(mmol·L^-1), and the detection limit is13.94mol·L^-1. And thepresence of ascorbic acid, hydrogen peroxide, glutathione, sucrose and lactose doesnot have obvious effect on the detection of glucose, showing that the prepared catalystdisplays excellent selectivity for the glucose detection. The electrode is a promisingelectrochemical sensor for the detection of low concentrations of glucose.（4） The different morphologies of copper-silver bimetallic nano-particles areprepared by the method of electro-deposition in Ag（NH₃）₂⁺+Cu（NH₃）₄²⁺solution.The results show that dipping a small amount of copper into the nanometer silvermaterial can increase the electro-catalytic activity of the nanometer silver electrodefor oxygen reduction.（5） Binary dendrite-like AgSn nano-particles are prepared by theelectro-deposition of Sn on the dendrite-like Ag nano-particles （Ag/Ti）. In alkalinesolution, Ag/Ti and AgSn/Ti electrodes exhibit excellent electro-activity for ORRwith the exchange current density of4.55×10-4mA·cm^-2.（6） The nano AgCo binary metal particles and their polyaniline modified catalystsare prepared by the method of electro-deposition. Their catalytic activity for ORR hasalso been studied. In alkaline solution, Ag/Ti, AgCo/Ti and their polyaniline modifiedelectrodes show excellent electrocatalytic activity for ORR. The ORR current densityat-0.12V（vs Ag/AgCl） reaches1.2mA·cm^-2. The electrocatalysts areelectrochemically insensitive to methanol and ethanol oxidation, and, as cathodeelectrocatalysts of direct alcohol fuel cells, can resist poisoning by the possiblealcohol crossover from the anode.