无码精品人妻一区二区三区影院_国产乱子经典视频在线观看_亚洲国产精品sss在线观看av_国产国语在线播放视频

NaPO3與SDBS緩蝕劑對AZ31鎂合金空氣電池在NaCl電解液中放電性能的影響

2020-11-04 01:31:49 hualin

摘要:

研究(jiu)了(le)(le)(le)以鑄(zhu)態AZ31鎂合(he)金為陽極(ji)(ji)(ji)材料的(de)鎂空(kong)氣電(dian)池在(zai)加(jia)入了(le)(le)(le)0.5 g/L NaPO3、0.5 g/L十二(er)烷基苯磺酸鈉(na) (SDBS)、0.5 g/L NaPO3+0.5 g/L SDBS作為緩(huan)(huan)蝕(shi)劑的(de)3.5% (質量分數) NaCl電(dian)解液(ye)中的(de)放電(dian)性能,測試了(le)(le)(le)AZ31鎂合(he)金在(zai)不(bu)(bu)同緩(huan)(huan)蝕(shi)劑溶液(ye)中的(de)自腐蝕(shi)速率、動(dong)電(dian)位極(ji)(ji)(ji)化(hua)曲(qu)線、EIS譜(pu),并使用(yong)SEM觀察了(le)(le)(le)陽極(ji)(ji)(ji)材料在(zai)不(bu)(bu)同緩(huan)(huan)蝕(shi)劑溶液(ye)中的(de)放電(dian)形貌。結果表明(ming),加(jia)入緩(huan)(huan)蝕(shi)劑可以較好(hao)地(di)抑制析氫腐蝕(shi),提高(gao)陽極(ji)(ji)(ji)利用(yong)率,弱化(hua)陽極(ji)(ji)(ji)極(ji)(ji)(ji)化(hua),提高(gao)放電(dian)電(dian)壓(ya)。其中在(zai)NaPO3+SDBS緩(huan)(huan)蝕(shi)劑溶液(ye)中,鎂空(kong)氣電(dian)池陽極(ji)(ji)(ji)腐蝕(shi)最弱,緩(huan)(huan)蝕(shi)效率可以達到(dao)85%,陽極(ji)(ji)(ji)利用(yong)率達到(dao)43.2%。


關(guan)鍵詞: 鎂空氣電池(chi) ; 緩蝕劑(ji) ; 陽極(ji)利用率(lv) ; 放電電壓


Mg是一(yi)種輕金(jin)(jin)屬(shu),密(mi)度為(wei)(wei)(wei)1.74 g/cm3,化學(xue)性質活潑,標準電極電位為(wei)(wei)(wei)-2.37 V (vsSHE)。以(yi)Mg為(wei)(wei)(wei)陽極組(zu)裝(zhuang)成電池可(ke)以(yi)形成較大(da)的(de)工作(zuo)電壓(ya)(ya),理(li)(li)論比容量(liang)為(wei)(wei)(wei)2205 mAh/g,僅次于金(jin)(jin)屬(shu)Li和(he)Al。且Mg及(ji)其放電產物無毒(du)、污染小、對環(huan)境友(you)好,是一(yi)種理(li)(li)想的(de)電極材料[1]。鎂空氣電池具(ju)有(you)高(gao)的(de)理(li)(li)論能量(liang)密(mi)度 (6.8 kWh/kg),高(gao)的(de)理(li)(li)論放電電壓(ya)(ya) (3.09 V),原(yuan)材料來源(yuan)(yuan)(yuan)豐富(fu)及(ji)成本(ben)低等(deng)(deng)特點,在移動電子設備電源(yuan)(yuan)(yuan)、海洋水下儀(yi)器電源(yuan)(yuan)(yuan)、自主(zhu)式潛(qian)航器電源(yuan)(yuan)(yuan)和(he)備用電源(yuan)(yuan)(yuan)等(deng)(deng)領域應用前景廣闊(kuo),被稱為(wei)(wei)(wei)21世紀最具(ju)有(you)潛(qian)力的(de)能源(yuan)(yuan)(yuan)[2,3,4]。


Mg本(ben)身化(hua)學性質(zhi)活潑,以鎂(mei)(mei)合(he)金(jin)(jin)作(zuo)(zuo)為(wei)(wei)陽極(ji)在電(dian)(dian)(dian)(dian)解(jie)(jie)液里容易發生析氫腐蝕,從而導致很(hen)(hen)大(da)部分(fen)(fen)鎂(mei)(mei)陽極(ji)的(de)(de)(de)消耗未用(yong)于(yu)放(fang)(fang)電(dian)(dian)(dian)(dian),因而利用(yong)率(lv)(lv)低,電(dian)(dian)(dian)(dian)池的(de)(de)(de)能(neng)(neng)量(liang)密(mi)(mi)度遠達(da)不(bu)到(dao)理論(lun)能(neng)(neng)量(liang)密(mi)(mi)度。此外(wai),由于(yu)其反應產(chan)物(wu)Mg(OH)2在電(dian)(dian)(dian)(dian)極(ji)表面附(fu)著,不(bu)能(neng)(neng)及(ji)時脫落,導致鎂(mei)(mei)陽極(ji)的(de)(de)(de)溶(rong)解(jie)(jie)不(bu)及(ji)時,造成(cheng)電(dian)(dian)(dian)(dian)極(ji)極(ji)化(hua)現象,導致鎂(mei)(mei)空(kong)氣(qi)(qi)電(dian)(dian)(dian)(dian)池放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)遠低于(yu)理論(lun)放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)。在電(dian)(dian)(dian)(dian)解(jie)(jie)液里加入適(shi)當的(de)(de)(de)緩(huan)蝕劑(ji),不(bu)僅(jin)操作(zuo)(zuo)簡單(dan)而且對鎂(mei)(mei)空(kong)氣(qi)(qi)電(dian)(dian)(dian)(dian)池的(de)(de)(de)性能(neng)(neng)有(you)(you)很(hen)(hen)大(da)的(de)(de)(de)提(ti)升(sheng)(sheng)。Dinesh等[5]以水(shui)溶(rong)性石(shi)墨烯(xi)作(zuo)(zuo)為(wei)(wei)添加劑(ji)加入到(dao)鎂(mei)(mei)空(kong)氣(qi)(qi)電(dian)(dian)(dian)(dian)池的(de)(de)(de)電(dian)(dian)(dian)(dian)解(jie)(jie)液中,有(you)(you)效(xiao)地(di)避免了(le)放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)突然下(xia)降,而且陽極(ji)材料(liao)的(de)(de)(de)腐蝕速率(lv)(lv)明(ming)顯(xian)降低。張(zhang)赟(yun)[6]分(fen)(fen)別(bie)向鎂(mei)(mei)空(kong)氣(qi)(qi)電(dian)(dian)(dian)(dian)池中加入六次(ci)甲(jia)基四胺與(yu)錫酸(suan)(suan)鈉,其放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)都有(you)(you)較(jiao)為(wei)(wei)明(ming)顯(xian)的(de)(de)(de)提(ti)升(sheng)(sheng),比容量(liang)分(fen)(fen)別(bie)達(da)到(dao)833.74和1029.74 mAh·g-1。按照緩(huan)蝕劑(ji)的(de)(de)(de)化(hua)學組成(cheng)一(yi)般(ban)分(fen)(fen)為(wei)(wei)有(you)(you)機(ji)(ji)緩(huan)蝕劑(ji)與(yu)無(wu)機(ji)(ji)緩(huan)蝕劑(ji)。無(wu)機(ji)(ji)緩(huan)蝕劑(ji)主(zhu)要有(you)(you)磷酸(suan)(suan)鹽(yan)、硅(gui)酸(suan)(suan)鹽(yan)、鉻酸(suan)(suan)鹽(yan)等。其中,硅(gui)酸(suan)(suan)鹽(yan)容易形成(cheng)硅(gui)垢且成(cheng)膜(mo)時間較(jiao)長,不(bu)利于(yu)提(ti)高鎂(mei)(mei)空(kong)氣(qi)(qi)電(dian)(dian)(dian)(dian)池放(fang)(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya);鉻酸(suan)(suan)鹽(yan)有(you)(you)毒,易對環境(jing)造成(cheng)污染(ran)。有(you)(you)機(ji)(ji)緩(huan)蝕劑(ji)主(zhu)要包括胺類(lei)和醛(quan)類(lei)等。有(you)(you)學者報道了(le)單(dan)獨使用(yong)有(you)(you)機(ji)(ji)緩(huan)蝕劑(ji)十二烷(wan)基苯磺酸(suan)(suan)鈉 (SDBS) 對鎂(mei)(mei)合(he)金(jin)(jin)的(de)(de)(de)緩(huan)蝕效(xiao)率(lv)(lv)提(ti)高不(bu)是很(hen)(hen)明(ming)顯(xian)[7]。因此,有(you)(you)機(ji)(ji)、無(wu)機(ji)(ji)緩(huan)蝕劑(ji)混合(he)使用(yong)成(cheng)為(wei)(wei)鎂(mei)(mei)空(kong)氣(qi)(qi)電(dian)(dian)(dian)(dian)池研究(jiu)的(de)(de)(de)一(yi)個(ge)熱點。本(ben)實(shi)驗主(zhu)要研究(jiu)了(le)以0.5 g/L NaPO3、0.5 g/L SDBS和0.5 g/L NaPO3+0.5 g/L SDBS作(zuo)(zuo)為(wei)(wei)緩(huan)蝕劑(ji)對AZ31鎂(mei)(mei)合(he)金(jin)(jin)陽極(ji)材料(liao)電(dian)(dian)(dian)(dian)化(hua)學性能(neng)(neng)的(de)(de)(de)影響作(zuo)(zuo)用(yong),及(ji)其所組成(cheng)鎂(mei)(mei)空(kong)氣(qi)(qi)電(dian)(dian)(dian)(dian)池的(de)(de)(de)放(fang)(fang)電(dian)(dian)(dian)(dian)性能(neng)(neng)。


1 實驗(yan)方(fang)法


1.1 實驗材料(liao)


陽極(ji)(ji)材料(liao)AZ31鎂(mei)合(he)金(jin)為(wei)(wei)(wei)湖南岳陽宇航(hang)新材料(liao)有限公(gong)司生(sheng)產(chan),其化學成分(fen) (質量分(fen)數,%) 為(wei)(wei)(wei):Al 3.12,Zn 1.04,Mn 0.44,Si 0.006,Fe 0.001,Cu 0.001,Mg余量。用(yong)(yong)線切(qie)割將試樣(yang)切(qie)成40 mm×10 mm×3 mm (用(yong)(yong)于電池(chi)放(fang)電測試) 和(he)(he)10 mm×10 mm×8 mm (用(yong)(yong)于電化學測試和(he)(he)全(quan)浸(jin)泡實驗) 兩種尺寸。將切(qie)好的試樣(yang)用(yong)(yong)400#,800#,1000#,1500#和(he)(he)2000#砂紙依次打磨(mo),最(zui)后(hou)丙酮除油、酒精清洗,冷風(feng)吹干備用(yong)(yong)。電解(jie)液(ye)為(wei)(wei)(wei)3.5% (質量分(fen)數) NaCl溶(rong)(rong)液(ye),緩蝕劑分(fen)別為(wei)(wei)(wei)0.5 g/L NaPO3,0.5 g/L SDBS和(he)(he)0.5 g/L NaPO3+0.5 g/L SDBS。所(suo)用(yong)(yong)試劑均為(wei)(wei)(wei)分(fen)析純,溶(rong)(rong)液(ye)采用(yong)(yong)去離子水配制。陰(yin)極(ji)(ji)為(wei)(wei)(wei)自制的空氣電極(ji)(ji),由防水層(ceng)(ceng)、鎳(nie)網、催化層(ceng)(ceng)3層(ceng)(ceng)組成,催化劑為(wei)(wei)(wei)MnO2。


1.2 靜態(tai)失重實驗


將準備好的試樣稱重 (W0)。在加入不同(tong)緩蝕劑(ji)的溶(rong)液中以懸(xuan)掛的方(fang)式浸(jin)泡72 h;然(ran)后取出,在含鉻酸(suan)的溶(rong)液中清洗5~10 min,除掉表面腐(fu)蝕產物;再(zai)經去(qu)離子水清洗后干燥,稱重 (W1)。腐(fu)蝕速(su)率V和(he)緩蝕效率IE分別用如(ru)下兩式計(ji)算:

微信截圖_20201021155023.jpg

式(shi)中,A為(wei)(wei)試樣表(biao)面(mian)積 (cm2),t為(wei)(wei)浸泡(pao)時(shi)間 (h)。V和V0分別是AZ31鎂合金(jin)在空白溶液 (不(bu)添加緩(huan)蝕劑的(de)3.5%NaCl溶液) 和加入緩(huan)蝕劑的(de)溶液中的(de)腐蝕速率。


1.3 電化學測試


測試采(cai)用(yong)(yong)三電(dian)極系統,將(jiang)準備好(hao)(hao)的(de)AZ31鎂合金用(yong)(yong)環氧(yang)樹(shu)脂(zhi)進(jin)行密封(feng),裸露面積為(wei)1 cm2(工作(zuo)電(dian)極),輔助電(dian)極為(wei)石墨片,參(can)比電(dian)極為(wei)飽和(he)甘汞電(dian)極 (SCE),電(dian)化學(xue)工作(zuo)站為(wei)CHI660C。電(dian)化學(xue)阻抗譜 (EIS) 測定在開路(lu)電(dian)位下進(jin)行,開路(lu)電(dian)位的(de)測試時間為(wei)1000 s,交流激勵信號峰(feng)值為(wei)5 mV,頻率(lv)(lv)范(fan)圍(wei)為(wei)105~10-1Hz。極化曲線掃(sao)(sao)描速率(lv)(lv)為(wei)1 mV/s,掃(sao)(sao)描范(fan)圍(wei)為(wei)-2.0~-1.0 V。將(jiang)封(feng)裝好(hao)(hao)的(de)試樣浸(jin)入相(xiang)應溶液中,待體(ti)系穩定后進(jin)行電(dian)化學(xue)測試。緩蝕效率(lv)(lv)IE分別用(yong)(yong)式 (3) 和(he) (4) 計算(suan):

微信截圖_20201021155015.jpg

式中,I0corr和(he)(he)Icorr分別為(wei)AZ31鎂合金(jin)試樣在空白和(he)(he)添(tian)加緩蝕劑后(hou)3.5%NaCl溶液中的腐(fu)蝕電(dian)(dian)(dian)流密度(du);R0t和(he)(he)Rt分別為(wei)等效電(dian)(dian)(dian)路圖中AZ31鎂合金(jin)試樣在空白和(he)(he)添(tian)加緩蝕劑后(hou)3.5%NaCl溶液中的電(dian)(dian)(dian)荷轉移電(dian)(dian)(dian)阻。


1.4 電池放(fang)電測試


將組(zu)裝好的(de)鎂空氣電池以20 mA·cm-2的(de)電流放電300 min,測試(shi)(shi)系統為CT2001ALAND型放電測試(shi)(shi)系統。陽極材料在測試(shi)(shi)前后(hou)分(fen)別(bie)稱重,記錄放電前后(hou)的(de)質量損失。用(yong)JSM-5610LV型掃描電鏡(SEM)觀察試(shi)(shi)樣放電后(hou)的(de)腐蝕形(xing)貌,用(yong)下式計算陽極利(li)用(yong)效率(lv):

微信截圖_20201021155006.jpg

式中,i為(wei)放(fang)電(dian)電(dian)流 (A),a為(wei)放(fang)電(dian)時間 (S),Ma為(wei)鎂合金的(de)相(xiang)對分子質量,F為(wei)Faraday常(chang)數,Wi和(he)Wf分別為(wei)電(dian)池放(fang)電(dian)前后的(de)質量 (g)。


2 結果與討論


2.1 浸泡失重實驗(yan)


根據式(shi) (1) 和(he) (2) 得(de)(de)出(chu)AZ31鎂(mei)(mei)合金(jin)(jin)在(zai)(zai)不(bu)同(tong)(tong)(tong)緩(huan)(huan)蝕(shi)(shi)(shi)劑(ji)溶液(ye)中的(de)(de)(de)(de)腐(fu)蝕(shi)(shi)(shi)速率(lv)與(yu)緩(huan)(huan)蝕(shi)(shi)(shi)速率(lv),如表(biao)(biao)1所(suo)示(shi)。可以看(kan)出(chu),加入緩(huan)(huan)蝕(shi)(shi)(shi)劑(ji)后,AZ31鎂(mei)(mei)合金(jin)(jin)的(de)(de)(de)(de)腐(fu)蝕(shi)(shi)(shi)速率(lv)明顯(xian)降(jiang)低(di)。但是(shi),單一添加劑(ji)對鎂(mei)(mei)合金(jin)(jin)的(de)(de)(de)(de)緩(huan)(huan)蝕(shi)(shi)(shi)效(xiao)果并不(bu)理想,而在(zai)(zai)NaPO3+SDBS的(de)(de)(de)(de)緩(huan)(huan)蝕(shi)(shi)(shi)劑(ji)溶液(ye)中緩(huan)(huan)蝕(shi)(shi)(shi)效(xiao)率(lv)最高,達到(dao)(dao)85%。這(zhe)是(shi)因(yin)為(wei)鎂(mei)(mei)合金(jin)(jin)的(de)(de)(de)(de)腐(fu)蝕(shi)(shi)(shi)主要是(shi)由Cl-的(de)(de)(de)(de)侵(qin)(qin)蝕(shi)(shi)(shi)造成(cheng)(cheng),AZ31鎂(mei)(mei)合金(jin)(jin)可以與(yu)電(dian)(dian)解液(ye)反(fan)(fan)應生(sheng)(sheng)成(cheng)(cheng)一層(ceng)疏(shu)松多(duo)(duo)孔(kong)的(de)(de)(de)(de)氧化膜(mo),這(zhe)層(ceng)膜(mo)不(bu)足以抵(di)擋Cl-的(de)(de)(de)(de)侵(qin)(qin)蝕(shi)(shi)(shi)。當Cl-侵(qin)(qin)蝕(shi)(shi)(shi)的(de)(de)(de)(de)部(bu)位暴露在(zai)(zai)電(dian)(dian)解液(ye)中,其(qi)會與(yu)電(dian)(dian)解液(ye)及周圍(wei)的(de)(de)(de)(de)鈍化膜(mo)組(zu)成(cheng)(cheng)小負極(ji)、大正極(ji)的(de)(de)(de)(de)原電(dian)(dian)池,從(cong)而加速Mg基(ji)體(ti)的(de)(de)(de)(de)點蝕(shi)(shi)(shi)。當加入NaPO3時(shi),其(qi)與(yu)電(dian)(dian)解液(ye)中的(de)(de)(de)(de)Mg2+發(fa)生(sheng)(sheng)反(fan)(fan)應生(sheng)(sheng)成(cheng)(cheng)Mg(PO3)2,如式(shi) (6) 所(suo)示(shi)。Mg(PO3)2的(de)(de)(de)(de)溶度積(ji)為(wei)1.04×10-24,相比于(yu)Mg(OH)2的(de)(de)(de)(de)1.2×10-11要小得(de)(de)多(duo)(duo),因(yin)此Mg(PO3)2比Mg(OH)2要更易于(yu)沉積(ji)。沉積(ji)在(zai)(zai)鎂(mei)(mei)合金(jin)(jin)表(biao)(biao)面(mian)的(de)(de)(de)(de)Mg(PO3)2膜(mo)層(ceng)相對于(yu)原始的(de)(de)(de)(de)膜(mo)層(ceng)顯(xian)得(de)(de)更加致(zhi)密平整。而SDBS屬于(yu)吸附型緩(huan)(huan)蝕(shi)(shi)(shi)劑(ji)[8,9],可以吸附在(zai)(zai)鎂(mei)(mei)基(ji)體(ti)與(yu)Mg(OH)2膜(mo)層(ceng)的(de)(de)(de)(de)表(biao)(biao)面(mian),形成(cheng)(cheng)有效(xiao)的(de)(de)(de)(de)疏(shu)水層(ceng),從(cong)而阻擋Cl-的(de)(de)(de)(de)侵(qin)(qin)蝕(shi)(shi)(shi)。當NaPO3與(yu)SDBS同(tong)(tong)(tong)時(shi)使(shi)用時(shi),沉積(ji)在(zai)(zai)基(ji)體(ti)相的(de)(de)(de)(de)Mg(PO3)2將(jiang)使(shi)原本疏(shu)松多(duo)(duo)孔(kong)的(de)(de)(de)(de)膜(mo)層(ceng)更為(wei)致(zhi)密。同(tong)(tong)(tong)時(shi),主要吸附在(zai)(zai)Mg(OH)2膜(mo)層(ceng)表(biao)(biao)面(mian)、Mg(PO3)2多(duo)(duo)孔(kong)處和(he)鎂(mei)(mei)基(ji)體(ti)處的(de)(de)(de)(de)SDBS使(shi)得(de)(de)這(zhe)層(ceng)致(zhi)密膜(mo)層(ceng)更為(wei)穩定(ding),NaPO3與(yu)SDBS表(biao)(biao)現(xian)出(chu)很好的(de)(de)(de)(de)協同(tong)(tong)(tong)作用,其(qi)緩(huan)(huan)蝕(shi)(shi)(shi)效(xiao)果達到(dao)(dao)最好。

表1   AZ31鎂合金(jin)在不(bu)同緩蝕(shi)劑溶(rong)液中的腐蝕(shi)速(su)率與緩蝕(shi)效率

微信截圖_20201021154956.jpg

圖1為AZ31鎂(mei)合金(jin)(jin)在(zai)(zai)含不同緩(huan)蝕(shi)劑3.5%NaCl溶液(ye)中的(de)(de)腐(fu)(fu)蝕(shi)形貌。從圖1a中空白溶液(ye)的(de)(de)腐(fu)(fu)蝕(shi)形貌可以看(kan)出(chu),鎂(mei)合金(jin)(jin)出(chu)現(xian)較多(duo)的(de)(de)點蝕(shi)坑,腐(fu)(fu)蝕(shi)非(fei)常(chang)嚴重(zhong)。圖1b和(he)c為添加單(dan)一緩(huan)蝕(shi)劑溶液(ye)中的(de)(de)腐(fu)(fu)蝕(shi)形貌,可看(kan)出(chu)點蝕(shi)坑變小,明顯(xian)可見(jian)砂紙打磨過的(de)(de)痕(hen)跡,但是其(qi)緩(huan)蝕(shi)效果并不是很明顯(xian)。圖1d為AZ31鎂(mei)合金(jin)(jin)在(zai)(zai)NaPO3+SDBS作(zuo)為緩(huan)蝕(shi)劑的(de)(de)溶液(ye)中的(de)(de)腐(fu)(fu)蝕(shi)形貌。可見(jian),腐(fu)(fu)蝕(shi)非(fei)常(chang)均勻,未觀(guan)察(cha)到點蝕(shi)坑,緩(huan)蝕(shi)效果最好。該結果與表(biao)1所得到的(de)(de)腐(fu)(fu)蝕(shi)速率和(he)緩(huan)蝕(shi)效率都十分吻合。

421379ae-48f5-43b1-ba96-4089ef74dd73-F006.jpg

圖1   AZ31鎂合金在添(tian)加不同(tong)緩蝕劑(ji)的3.5%NaCl溶液中的腐蝕形貌


2.2 電化學測(ce)試結果


2.2.1 動電(dian)位(wei)極化(hua)


圖2為(wei)AZ31鎂合金在(zai)(zai)不同緩(huan)蝕(shi)劑(ji)溶(rong)液中的(de)(de)(de)(de)Tafel曲線。可以看出(chu),加(jia)入緩(huan)蝕(shi)劑(ji)后,自(zi)腐(fu)(fu)蝕(shi)電(dian)(dian)位(wei)(wei)Ecorr均(jun)負移,活化(hua)(hua)性能得(de)到提(ti)高,說(shuo)(shuo)明緩(huan)蝕(shi)劑(ji)的(de)(de)(de)(de)加(jia)入可以提(ti)高電(dian)(dian)池的(de)(de)(de)(de)放電(dian)(dian)電(dian)(dian)壓。在(zai)(zai)含NaPO3+SDBS緩(huan)蝕(shi)劑(ji)溶(rong)液中,陽極(ji)(ji)極(ji)(ji)化(hua)(hua)曲線上出(chu)現(xian)了明顯的(de)(de)(de)(de)鈍化(hua)(hua)平臺;電(dian)(dian)位(wei)(wei)約為(wei)-1.49 V時(shi),電(dian)(dian)流迅速增大,表現(xian)出(chu)鈍化(hua)(hua)膜的(de)(de)(de)(de)破壞,此電(dian)(dian)位(wei)(wei)即點蝕(shi)電(dian)(dian)位(wei)(wei)。陰極(ji)(ji)極(ji)(ji)化(hua)(hua)曲線在(zai)(zai)添加(jia)緩(huan)蝕(shi)劑(ji)前后從形狀上來(lai)說(shuo)(shuo)是相(xiang)似(si)的(de)(de)(de)(de),這也就意(yi)味著(zhu)陰極(ji)(ji)析氫(qing)反應過程類似(si)[10]。根(gen)據(ju)(ju)Tafel外推法(fa)在(zai)(zai)強極(ji)(ji)化(hua)(hua)區擬合的(de)(de)(de)(de)數(shu)據(ju)(ju)見(jian)表2所示。腐(fu)(fu)蝕(shi)電(dian)(dian)流密度(du)隨著(zhu)添加(jia)劑(ji)的(de)(de)(de)(de)加(jia)入表現(xian)出(chu)減(jian)小的(de)(de)(de)(de)趨(qu)勢,在(zai)(zai)NaPO3+SDBS緩(huan)蝕(shi)劑(ji)溶(rong)液中腐(fu)(fu)蝕(shi)電(dian)(dian)流密度(du)達(da)到最(zui)小 (2.616×10-5A·cm-2)。根(gen)據(ju)(ju)式(shi) (3) 計(ji)算(suan)得(de)到的(de)(de)(de)(de)緩(huan)蝕(shi)效(xiao)率(lv)(lv)(lv)可知,在(zai)(zai)兩種緩(huan)蝕(shi)劑(ji)溶(rong)液都加(jia)入的(de)(de)(de)(de)情況(kuang)下(xia),其緩(huan)蝕(shi)效(xiao)率(lv)(lv)(lv)達(da)到92.2%,這與靜態失(shi)(shi)重法(fa)獲(huo)(huo)得(de)的(de)(de)(de)(de)緩(huan)蝕(shi)效(xiao)率(lv)(lv)(lv)的(de)(de)(de)(de)數(shu)據(ju)(ju)并不是完全的(de)(de)(de)(de)一致。這是因為(wei)電(dian)(dian)化(hua)(hua)學方(fang)法(fa)計(ji)算(suan)的(de)(de)(de)(de)是瞬時(shi)腐(fu)(fu)蝕(shi)速率(lv)(lv)(lv),靜態失(shi)(shi)重法(fa)算(suan)獲(huo)(huo)得(de)的(de)(de)(de)(de)是浸泡72 h的(de)(de)(de)(de)平均(jun)腐(fu)(fu)蝕(shi)速率(lv)(lv)(lv),但緩(huan)蝕(shi)效(xiao)果總體趨(qu)勢變化(hua)(hua)是一致的(de)(de)(de)(de)。

421379ae-48f5-43b1-ba96-4089ef74dd73-F001.jpg

圖2   AZ31鎂合金(jin)在不同緩蝕劑溶液(ye)中(zhong)的Tafel曲線(xian)

表2   AZ31鎂(mei)合(he)金在不(bu)同緩蝕劑溶液中的Tafel曲線擬合(he)數據

微信截圖_20201021154939.jpg

2.2.2 電化學阻抗譜


圖(tu)3為(wei)AZ31鎂(mei)(mei)合金在含不同緩蝕劑(ji)3.5%NaCl溶(rong)(rong)液(ye)中(zhong)的(de)(de)Nyquist圖(tu)。可以看出,在空白(bai)溶(rong)(rong)液(ye)以及(ji)含單一(yi)NaPO3或SDBS緩蝕劑(ji)溶(rong)(rong)液(ye)中(zhong),AZ31鎂(mei)(mei)合金的(de)(de)阻抗(kang)譜相(xiang)似,在高頻區域為(wei)容抗(kang)弧,低(di)(di)頻區域為(wei)感抗(kang)弧。感抗(kang)弧的(de)(de)出現表明陽(yang)極溶(rong)(rong)解(jie)過(guo)程中(zhong)存(cun)在中(zhong)間產物[11]。而在NaPO3+SDBS緩蝕劑(ji)溶(rong)(rong)液(ye)中(zhong),阻抗(kang)譜的(de)(de)高、低(di)(di)頻均為(wei)容抗(kang)弧,表明電(dian)極表面(mian)(mian)由膜完整覆蓋(gai)。高頻容抗(kang)弧是(shi)由Rt及(ji)雙電(dian)層(ceng)界面(mian)(mian)電(dian)容CPE組成的(de)(de)阻容弛豫過(guo)程引起(qi),弧半徑的(de)(de)大(da)小反映了腐蝕阻力的(de)(de)大(da)小[12]。隨著緩蝕劑(ji)的(de)(de)加入,高頻容抗(kang)弧半徑明顯增大(da),說(shuo)明溶(rong)(rong)液(ye)傳遞電(dian)阻逐漸增大(da),耐蝕性變好。

421379ae-48f5-43b1-ba96-4089ef74dd73-F002.jpg

圖(tu)3   AZ31鎂合金在含不同緩蝕(shi)劑溶液中(zhong)的Nyquist圖(tu)


圖(tu)4a為(wei)(wei)AZ31鎂合(he)金(jin)在空(kong)白溶(rong)(rong)液(ye)以及添(tian)加單(dan)一(yi)NaPO3或SDBS緩(huan)蝕劑溶(rong)(rong)液(ye)中的(de)等效(xiao)電(dian)(dian)路(lu),圖(tu)4b為(wei)(wei)在復合(he)添(tian)加NaPO3+SDBS緩(huan)蝕劑溶(rong)(rong)液(ye)中的(de)等效(xiao)電(dian)(dian)路(lu)。其中,Rs為(wei)(wei)溶(rong)(rong)液(ye)電(dian)(dian)阻,L為(wei)(wei)電(dian)(dian)感,R1為(wei)(wei)膜(mo)值(zhi)電(dian)(dian)阻。表3為(wei)(wei)擬合(he)得到的(de)阻抗譜數據。可(ke)以看(kan)出,隨著電(dian)(dian)解液(ye)中緩(huan)釋(shi)劑的(de)加入,Rt明顯增加。根(gen)據式 (4) 計算(suan)可(ke)知(zhi),AZ31鎂合(he)金(jin)在含NaPO3+SDBS的(de)溶(rong)(rong)液(ye)中緩(huan)蝕效(xiao)率最高,達(da)到90%。

421379ae-48f5-43b1-ba96-4089ef74dd73-F003.jpg

圖(tu)4   ;AZ31鎂合金在(zai)含不同緩蝕劑溶(rong)液(ye)中的(de)等效電路圖(tu)

表3   AZ31鎂合金在不(bu)同緩(huan)蝕(shi)劑溶(rong)液(ye)中等效(xiao)電(dian)路圖(tu)的擬(ni)合數據

微信截圖_20201021154924.jpg

2.3 電池放電測(ce)試


圖(tu)5為(wei)(wei)AZ31鎂(mei)合(he)金(jin)作(zuo)為(wei)(wei)陽(yang)極(ji)材料(liao)與(yu)(yu)自制陰極(ji)以及不同電(dian)(dian)(dian)解液所(suo)(suo)組(zu)成的(de)(de)(de)鎂(mei)空氣(qi)電(dian)(dian)(dian)池(chi),在(zai)20 mA·cm-2電(dian)(dian)(dian)流(liu)(liu)密度(du)下放(fang)(fang)電(dian)(dian)(dian)60~300 min的(de)(de)(de)恒流(liu)(liu)放(fang)(fang)電(dian)(dian)(dian)曲線(xian)(xian),圖(tu)中(zhong)(zhong)插圖(tu)為(wei)(wei)0~300 min的(de)(de)(de)放(fang)(fang)電(dian)(dian)(dian)曲線(xian)(xian)。可(ke)(ke)以看(kan)出,電(dian)(dian)(dian)池(chi)放(fang)(fang)電(dian)(dian)(dian)初期(qi)電(dian)(dian)(dian)壓降低,這(zhe)是(shi)所(suo)(suo)謂的(de)(de)(de)“電(dian)(dian)(dian)壓滯(zhi)后(hou)”現象(xiang)[13]。其實(shi)質是(shi)因為(wei)(wei)Mg負(fu)極(ji)電(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學活性(xing)較高,與(yu)(yu)電(dian)(dian)(dian)解液會(hui)生成一(yi)層鈍化(hua)(hua)(hua)(hua)膜(mo)(mo),電(dian)(dian)(dian)池(chi)剛(gang)開始工作(zuo)的(de)(de)(de)時(shi)候,鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)的(de)(de)(de)存在(zai)阻礙了(le)放(fang)(fang)電(dian)(dian)(dian)反應的(de)(de)(de)正(zheng)常進(jin)(jin)行;當電(dian)(dian)(dian)流(liu)(liu)擊穿(chuan)這(zhe)層鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)后(hou),反應才(cai)能順利進(jin)(jin)行,經過一(yi)小(xiao)段時(shi)間電(dian)(dian)(dian)池(chi)達(da)到正(zheng)常的(de)(de)(de)工作(zuo)電(dian)(dian)(dian)壓。所(suo)(suo)組(zu)裝成的(de)(de)(de)4種(zhong)空氣(qi)電(dian)(dian)(dian)池(chi)放(fang)(fang)電(dian)(dian)(dian)性(xing)能參數如表4所(suo)(suo)示。可(ke)(ke)以看(kan)出,隨(sui)著緩蝕劑的(de)(de)(de)加(jia)入,鎂(mei)空氣(qi)電(dian)(dian)(dian)池(chi)的(de)(de)(de)放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)壓有一(yi)個增高的(de)(de)(de)趨勢,其中(zhong)(zhong)在(zai)同時(shi)加(jia)入兩種(zhong)緩蝕劑的(de)(de)(de)情況下,放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)壓達(da)到最高 (1.081 V),陽(yang)極(ji)極(ji)化(hua)(hua)(hua)(hua)現象(xiang)得到很好的(de)(de)(de)弱(ruo)化(hua)(hua)(hua)(hua),腐蝕得到較好的(de)(de)(de)抑制,提高了(le)陽(yang)極(ji)利用率,達(da)到43.5%,提高了(le)6.9%。

421379ae-48f5-43b1-ba96-4089ef74dd73-F004.jpg

圖5   不同電解液鎂空氣電池在(zai)20 mA·cm-2條件(jian)下的放電曲線

表4   不同電解液(ye)鎂空氣電池在20 mA·cm-2條件下的放電參數

微信截圖_20201021154910.jpg

圖(tu)(tu)(tu)6為AZ31鎂合(he)金與不同電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液組(zu)成的(de)(de)鎂空(kong)(kong)氣(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)以20 mA·cm-2的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流密度(du)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)300 min后的(de)(de)形(xing)(xing)貌。鎂空(kong)(kong)氣(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)形(xing)(xing)貌與放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)性能(neng)有很大(da)(da)的(de)(de)關系[14,15,16]。可(ke)以看(kan)出(chu)(chu),每種材料表(biao)(biao)面(mian)(mian)都(dou)有細(xi)小的(de)(de)裂(lie)(lie)縫,這些細(xi)小裂(lie)(lie)縫的(de)(de)存在保證鎂基體與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解液有效的(de)(de)接觸(chu),以保證反應的(de)(de)正常進(jin)(jin)行(xing)。同時(shi)也可(ke)以看(kan)到,陽(yang)極(ji)(ji)(ji)(ji)表(biao)(biao)面(mian)(mian)有放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)產(chan)(chan)(chan)物(wu)(wu)堆積 (如(ru)箭頭所(suo)示)。從圖(tu)(tu)(tu)6a看(kan)出(chu)(chu),放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)產(chan)(chan)(chan)物(wu)(wu)大(da)(da)量堆積而且呈片(pian)狀(zhuang)結(jie)構,這些放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)產(chan)(chan)(chan)物(wu)(wu)會堵(du)在陽(yang)極(ji)(ji)(ji)(ji)表(biao)(biao)面(mian)(mian)的(de)(de)裂(lie)(lie)縫上阻礙(ai)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)反應的(de)(de)正常進(jin)(jin)行(xing),導致陽(yang)極(ji)(ji)(ji)(ji)極(ji)(ji)(ji)(ji)化的(de)(de)發生(sheng),此(ci)外還會導致鎂空(kong)(kong)氣(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)內阻變大(da)(da),電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)較低(di)。圖(tu)(tu)(tu)6b和c分別為加(jia)入NaPO3與SDBS的(de)(de)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)形(xing)(xing)貌。可(ke)以看(kan)出(chu)(chu),放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)產(chan)(chan)(chan)物(wu)(wu)在試樣表(biao)(biao)面(mian)(mian)的(de)(de)累積量明(ming)顯減少,但仍(reng)然(ran)呈大(da)(da)片(pian)狀(zhuang)結(jie)構。圖(tu)(tu)(tu)6d為加(jia)入NaPO3+SDBS的(de)(de)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)形(xing)(xing)貌。可(ke)以看(kan)出(chu)(chu),這兩(liang)種緩蝕劑都(dou)加(jia)入后堆積產(chan)(chan)(chan)物(wu)(wu)明(ming)顯減少,片(pian)狀(zhuang)的(de)(de)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)產(chan)(chan)(chan)物(wu)(wu)被細(xi)化成微(wei)小顆粒(li),從而弱化極(ji)(ji)(ji)(ji)化作用,保證電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)反應的(de)(de)正常進(jin)(jin)行(xing),所(suo)以該鎂空(kong)(kong)氣(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)會有明(ming)顯的(de)(de)提升。

421379ae-48f5-43b1-ba96-4089ef74dd73-F005.jpg

圖6   不同電解液鎂空氣電池以20 mA·cm-2的(de)電流密度(du)放(fang)電300 min的(de)放(fang)電形貌(mao)


3 結論


(1) 添加0.5 g/L NaPO3+0.5 g/L SBDS對AZ31鎂合金在3.5%NaCl溶液中具(ju)有較好(hao)的緩蝕(shi)效果(guo),較好(hao)地抑(yi)制腐蝕(shi),緩蝕(shi)效率達(da)到(dao)85%。以(yi)0.5 g/L NaPO3+0.5 g/L SDBS作為緩蝕(shi)劑加入到(dao)所組成(cheng)的鎂空氣電池中,陽極利用率達(da)到(dao)43.2%。


(2) 0.5 g/L NaPO3+0.5 g/L SBDS緩蝕(shi)劑(ji)的加入(ru),可(ke)以減少鎂空氣電(dian)池放(fang)(fang)電(dian)產物的堆積,細(xi)化放(fang)(fang)電(dian)產物顆粒從而(er)弱化陽極(ji)極(ji)化,提(ti)高(gao)放(fang)(fang)電(dian)電(dian)壓。以20 mA·cm-2的電(dian)流(liu)密(mi)度進行放(fang)(fang)電(dian)時,電(dian)壓可(ke)達到1.081 V。