【摘要】：隨著全球化石燃料的枯竭和環(huán)境污染問題日益嚴(yán)重,人們極力尋找一種新的能源來取代之。直接甲醇燃料電池(DMFCs)擁有極好的能量轉(zhuǎn)化率且對(duì)環(huán)境無污染,受到了人們廣泛的關(guān)注。直接甲醇燃料電池主要使用貴金屬Pt為催化劑,但Pt面臨著全球儲(chǔ)量稀少和價(jià)格高等問題,制約了直接甲醇燃料電池的大規(guī)模應(yīng)用。近年來,研究者開始把催化劑載體和助劑作為研究重點(diǎn),來降低貴金屬的使用量。其中多孔碳、碳化物和異質(zhì)原子摻雜是研究的熱點(diǎn)。在本論文中,我們使用多孔石墨(烯)半球、埃米尺度碳化釩和竹狀氮摻雜碳化鎢作為催化劑載體,來提高Pt的利用率以及Pt與載體結(jié)合的穩(wěn)定性,從而達(dá)到同時(shí)提高電催化甲醇氧化反應(yīng)活性和穩(wěn)定性的目的。1、利用實(shí)心核多孔殼二氧化硅小球(SCMSSs)為模版,葡萄糖為碳源,氯化鎳為石墨化催化劑,經(jīng)1000℃加熱、除模板和除雜質(zhì),制得了碗狀多孔石墨(半球)(GLBs);同時(shí)與未石墨化的多孔碳(BLCs)進(jìn)行比較。以它們?yōu)檩d體制備了Pt/GLB和Pt/BLC催化劑。物理表征結(jié)果表明,這種GLBs的直徑和SCMSSs的直徑一致,即前者完美的反向復(fù)制了SCMSSs的形貌,形成了多孔結(jié)構(gòu)和較大的比表面積,促進(jìn)了Pt顆粒的均勻分散且降低了Pt的粒徑。電化學(xué)測(cè)試表明,Pt/GLB催化甲醇氧化的峰電流密度(2075 mA mg_(Pt)~(-1))是商業(yè)Pt/C(723mA mg_(Pt)~(-1))的2.87倍,是Pt/BLC(1846 mA mg_(Pt)~(-1))的1.12倍,且Pt/GLB具有顯著提高的穩(wěn)定性和抗毒化性能。2、通過調(diào)節(jié)釩酸鈉和離子交換樹脂的配比制得了不同形貌的碳-碳化釩(C-V_8C_7)復(fù)合材料。物理表征結(jié)果表明,隨著釩酸鈉用量增加,碳化釩從平均寬度為0.8 nm的棒狀轉(zhuǎn)變?yōu)榱綖?0 nm左右的顆粒狀,且團(tuán)聚現(xiàn)象愈加明顯。在這些碳化釩材料上負(fù)載Pt制得相應(yīng)的Pt/C-V_8C_7催化劑。電化學(xué)測(cè)試結(jié)果顯示,棒狀Pt/C-V_8C_7(1605 mA mg_(Pt)~(-1))催化甲醇氧化的峰電流密度是顆粒狀Pt/C-V_8C_7(1377 mA mg_(Pt)~(-1))的1.78倍,是商業(yè)Pt/C(775 mA mg_(Pt)~(-1))的2.07倍。更有意義的是,在0.4 V時(shí),棒狀Pt/C-V_8C_7催化甲醇氧化的電流密度是Pt/C的9倍,表明前者在低電位下具有更高的優(yōu)勢(shì)。另外,兩個(gè)Pt/C-V_8C_7均比商業(yè)Pt/C具有更高的催化甲醇氧化的穩(wěn)定性。分析認(rèn)為,碳化物和貴金屬之間存在的電子轉(zhuǎn)移,改變了Pt的表面電子結(jié)構(gòu),提高了Pt和載體間的作用力,從而能夠同時(shí)提高Pt/C-V_8C_7電催化活性和穩(wěn)定性。3、使用三聚氰胺作為氮源和碳源,偏鎢酸銨為鎢源,制備了N摻雜的碳化鎢(NWC-1);另外,在制備過程中添加FeCl_3改變材料性質(zhì),制得NWC-2;Fe的存在還能夠提高材料的石墨化度。以它們?yōu)檩d體載Pt制得Pt/NWC-1和Pt/NWC-2催化劑,兩者Pt顆粒的尺寸均約為1.0 nm;但FeCl_3的存在使得NWC-2的形貌的更加均一,Pt在其表面的分散也相應(yīng)的更加均勻。電化學(xué)測(cè)試表明,Pt/NWC-2具有比Pt/NWC-1更高的催化甲醇氧化活性和穩(wěn)定性,以及更好的導(dǎo)電性;這歸因于NWC-2具有較高的石墨度和較均一的結(jié)構(gòu)。
[Abstract]:With the depletion of fossil fuels and environmental pollution in the world, people are looking for a new energy to replace it. Direct methanol fuel cell (DMFCs) has attracted much attention for its excellent energy conversion and no pollution to the environment. Noble metal Pt is mainly used as catalyst for direct methanol fuel cell (DMFC). However, Pt is faced with the problems of scarcity of global reserves and high price, which restricts the large-scale application of DMFC. In recent years, researchers began to focus on catalyst carriers and auxiliaries to reduce the use of precious metals. Among them, porous carbon, carbides and heteroatoms doping are the focus of research. In this thesis, porous graphite (ene) hemispheres, Emmy scale vanadium carbide and bamboo nitrogen doped tungsten carbide were used as catalyst supports to improve the utilization of Pt and the stability of Pt binding to the support. In order to improve the activity and stability of methanol oxidation by electrocatalysis simultaneously, the solid core porous shell silica pellet (SCMSSs) was used as template, glucose as carbon source, nickel chloride as graphitization catalyst, and heated at 1000 鈩，

本文編號(hào)：2211818