Studies On The Controlled Synthesis Of One-dimensional Ir-and Pt-based Nanocrystals And Their Properties

Iridium?Ir?-and Platinum?Pt?-based noble metals nanomaterials are of outstanding optical,electrical and catalytic properties,particularly playing a important role in fuel cell and hydrogenation reaction,where the catalytic effect directly affects the performance of fuel cell and hydrogenation reaction.Through controllable synthesizing Ir-and Pt-based noble metal nanomaterials with the various morphology and structure size,it provides a feasible method for the study of the high performance catalytic performance.Currently,one dimensional noble metal nanocrystals have attracted widely attention because of the preferred exposured reaction crystal surface,high structure stability and fast electron transfer rate and other advantages,which improving and strengthening the catalytic reaction conditions of the fuel cell and hydrogenation that attributed to the enhanced the catalytic performance.Therefore,designing rationaly a shape-controlled Ir-or Pt-based nanocrystals is of great significance.In this work,the morphology and surface structure of one-dimensional Ir-and Pt-based nanocrystals were controlled effectively,and Ir-Sn nanowires,Ir-Ag nanotubes and Pt-Sn nanowires were obtained successfully,respectively.Furthermore,the growth mechanism,structure and the relationship of structure-properties were also further explored.The specific content and main research results are summarized as follows:Chapter 1.Using iridium?III?chloride hydrate and Tin?II?acetate as precursors,citric acid?CA?as reducing agent,ethylene glycol?EG?was applied as solvent,ultrafine vein-like Ir-Sn nanowires with abundant oxidized tin were prepared by a simple hydrothermal method.The composition of Ir-Sn nanowires can be regulated by changing the feed of Sn precursor.Due to the ultrafine vein structure and abundant tin oxide surface.This Ir-Sn nanowire catalysts exhibited efficient ethanol oxidation at low potential performance,especially the optimal Ir₆₇Sn₃₃ nanowires exhibited best performance.Only the Ir₆₇Sn₃₃/C has a high oxidation peak at potential less than 0.1 V,with the excellent mass current density of 95.6 mA mg_Ir^-1 at 0.04 V,which is 4 and 20 times higher than Ir/C(23.5mA mg^-1)and Pt/C(4.9 mA mg^-1),respectively.The durabilities of the Ir₆₇Sn₃₃/C,Ir/C and Pt/C were also conducted at a constant potential of 0.09 V for 2 h,in which the Ir₆₇Sn₃₃/C exhibited superior duribility while Ir/C was nearly inactive after 1 h and Pt/C lost activity completely in a very short time.Chapter 2.A new class of hollow Ir-Ag nanotubes by simply chemical etching the original nanowires was reported for the first time.After thermal treatment of IrAg nanotubes under the condition of high temperature,which can remove excess surfactant and obtained abundant oxidized iridium.Because of these unique properties,the hollow Ir Ag nanotubes catalyst showed excellent activities and stability for the oxygen evolution reaction,hydrogen evolution reaction and overall water splitting catalysis in the acidic conditions.The optimized hollow Ir Ag NTs show low OER overpotentials of 285 mV and296 mV at 10 mA/cm² and excellent durability in 0.5 M and 0.05 M H₂SO₄ electrolytes,respectively,both which are superior than the commercial Ir/C.The hollow Ir Ag NTs also exhibit lower HER overpotentials?only 20 mV and 34 mV at 10 mA/cm² in 0.5 M and0.05 M H₂SO₄ electrolytes,respectively?and longer durability.The hollow Ir-Ag NTs can even deliver excellent performance for overall water splitting,achieving a very low cell voltage of only 1.55 V at 10 m A/cm² in 0.5 M H₂SO₄,and show enhanced durability with small activity loss after 1000 cycles,which outperforms the commercial Ir/C-Pt/C.Chapter 3.An efficient and facile synthetic method for the preparation of PtSn nanowires is proposed.The PtSn nanowires with different components can also be achieved by changing the amount of Sn precursor.In particular,the optimized Pt_1.5Sn NWs delivered an outstanding activityto hydrogenate cinnamaldehyde?nearly 100%conversion?and excellent selectivity to cinnamyl alcohol?90.6%?,which is superior to those of Pt_1.5Sn nanoparticles?NPs?and Pt NPs.Moreover,the other unsaturated aldehydes such as crotonaldehyde,3-methyl-2-butenal and furfural,which all also showed excellent conversion efficiency?over 90%?and selectivity to unsaturated alcohol?over 90%?.