수동형 직접 글리세롤 연료 전지에서 나노구조의 Pd 기반 전극 촉매 및 막 전극 조립 동작

결과 및 토론

전기 촉매 물리적 특성

Au/VGCNF, Pd/VGCNF 및 Pd₁인 3개의 합성된 전기 촉매 샘플에 대한 X선 회절 패턴 금₁ /VGCNF는 그림 1에, 분석 데이터는 표 1에 정리되어 있습니다. 전기촉매의 X선 회절 패턴은 두 번째 상이 없는 입방 구조(Fm-3m 공간군)를 보여줍니다. 26.0°에서 첫 번째 회절도 피크는 육각형 흑연(JCPDS 카드 파일 41-1487)의 원시 VGCNF 회절 평면의 흑연 구조 탄소(002)에 할당될 수 있습니다(Rajarao 및 Bhat [30]). 표시된 각 회절도 패턴에는 평면 (1 1 1), (2 0 0), (2 2 0) 및 (3 1 1) fcc에서 회절에 대해 인덱싱될 수 있는 4개의 회절 피크가 있습니다.

다양한 전기촉매 Pd₁의 회절도 금₁ /VGCNF, Pd/VGCNF 및 Au/VGCNF

그림 1은 약 38.3 °C, 44.5 °C, 64.7 °C 및 77.7 °C에서 Au/VGCNF 전기 촉매 샘플의 회절 피크를 보여주고 결정학적 평면(1 1 1), (2 0 0)에 대해 색인을 생성할 수 있습니다. 2 2 0) 및 (3 1 1), 각각 Fm-3m(JCPDS No. 65-8601, a =b =c =0.4072 nm)로 분류할 수 있습니다. 그림 1은 40.12 °C, 46.66 °C, 68.12 °C 및 82.10 °C의 2θ 값 주변에서 Pd/VGCNF 전기촉매 샘플의 회절 패턴을 보여줍니다. 이는 다음 평면 (1 1 1), (2 00)에 해당합니다. , (2 2 0), 및 (3 1 1) (JCPDS No. 05-0681, a =b =c =0.3889 nm). 그림 1에서 PdAu 바이메탈 샘플의 경우 Pd와 Au는 단일 회절 피크를 공유하는 것으로 나타나 균일한 합금 형성이 발생했음을 나타냅니다.

VGCNF에 지지된 일반적인 PdAu 나노 입자는 기본적으로 금속 전구체(즉, \( {\mathrm{AuCl}}_4^{-} \) 및 \( {\mathrm{PdCl}}_4^{ 2-} \)) 환원제로서 수소화붕소나트륨의 존재하에. 그림 2a–c는 Au/VGCNF, Pd/VGCNF 및 PdAu/VGCNF 전기촉매의 일반적인 TEM 이미지를 보여줍니다. Au, Pd 및 PdAu 나노입자 형태는 VGCNF에서 균일한 분포와 함께 적당한 정도의 응집 거동을 나타냄을 알 수 있습니다. 결정 구조 패턴은 SAED(selected area electron diffraction) 분석(그림 2a–c에 삽입)으로 분석되었으며 Au/VGCNF, Pd/VGCNF 및 PdAu/VGCNF가 일반적으로 fcc 다결정 구조임을 나타냅니다. 그림 2d, e에서 관찰된 고해상도 TEM(HRTEM) 이미지는 각각 Au 및 Pd에 대한 (111) 평면의 면간 거리에 해당하는 0.24 nm 및 0.22 nm의 간격 거리를 나타냅니다. 그림 2f는 d - 표시된 영역에서 결정된 격자 무늬의 간격 값은 면심 입방체(fcc) PdAu 합금의 (111) 평면에 해당하는 0.230 nm입니다.

아 –ㄷ Au/VGCNF, Pd/VGCNF 및 Pd에 대한 TEM 및 SAED 패턴의 일반적인 이미지₁ 금₁ /VGCNF. d –f Au/VGCNF, Pd/VGCNF 및 Pd₁에 대한 HRTEM 이미지 금₁ /VGCNF 전기촉매

BET 표면적 및 다공성 분석은 Au/VGCNF, Pd/VGCNF 및 Pd₁의 능력 평가를 위한 효과적인 도구입니다. 금₁ /VCGNF는 흡착제 역할을 합니다. BET는 흡착된 물질(흡착물)의 양과 고체(흡착제)의 흡착제 표면에 대한 흡착 정도를 나타냅니다[31]. Au/VGCNF, Pd/VGCNF 및 Pd₁의 BET 표면적 금₁ /VGCNF 샘플은 그림 3a와 같이 질소 흡탈착 등온선을 사용하여 분석되었습니다. 등온선 곡선은 등온선 모양을 반영하며 재료의 다공성에 대한 정성적 평가를 제공합니다. 이 연구에서 관찰된 등온선 모양은 Au/VGCNF, Pd/VGCNF 및 Pd₁ 금₁ /VCGNF는 유형 IV(IUPAC 분류 기준)로 확인되었으며 0.83–0.99 P/P₀의 상대 압력 범위에서 가파른 기울기를 나타냅니다. , 이는 메조포러스 물질의 존재 특성이다[32]. 메조포러스 구조를 가진 물질은 흡착량 증가로 인해 형태 안정성이 우수하고 촉매 활성이 높아 촉매 활성이 향상됩니다.

아 N₂ Au/VGCNF, Pd/VGCNF 및 Pd의 흡착/탈착 등온선₁ 금₁ /VGCNF. ㄴ Au/VGCNF, Pd/VGCNF 및 Pd₁의 기공 크기 분포 곡선 금₁ /VGCNF

전극촉매의 표면적, 기공 부피 및 기공 직경 값은 표 1에 나와 있습니다. 표에서 VGCNF의 표면적은 30.56 m ² 입니다. /g, 기공 부피 0.415 cm ³ /g 및 7.0 nm의 기공 직경. 촉매 지지체 위의 금속 촉매(Au, Pd 및 PdAu)의 존재는 표면적, 기공 부피 및 기공 직경을 감소시키는 것으로 밝혀졌습니다. 이것은 촉매 금속이 흩어져 촉매 지지체의 표면과 만나기 때문입니다. 촉매 금속이 VGCNF에 분산된 후에도 H1 유형 히스테리시스 루프(P/Po 0.83–0.99)는 재료의 메조기공 구조가 영향을 받지 않음을 나타냅니다. 촉매 금속이 촉매 지지체 표면에 균일하게 흩어져 있음을 나타내는 TEM 이미지와 일치하여 VGCNF 표면에 촉매 금속이 잘 퍼져 있음을 알 수 있습니다.

Au/VGCNF, Pd/VGCNF 및 Pd₁의 BJH 기공 크기 분포에서 알 수 있듯이 금₁ /VCGNF는 도 3a에 제시된 바와 같이 약 4 nm(세공 반경)에서 좁은 세공 직경 또는 세공 직경을 나타내는 반면, 모든 촉매에서 관찰되는 세공 크기 범위는 2~5 nm 사이에 위치하여 물질을 독특한 흡착제로 만듭니다. 중간 [31]. Au/VGCNF, Pd/VGCNF 및 Pd₁ 금₁ /VGCNF 전기촉매는 VGCNF에 비해 작은 기공 부피를 가지고 있는데, 이는 나노입자 장식 과정에서 지지체 매체 내부의 일부 다공성 공간이 금속 촉매 나노입자 또는 기타 화학 반응으로 차단되어 결과적으로 기공 부피가 감소하기 때문입니다. 그러나 보고된 BET 표면적은 전체 전기촉매 표면적을 의미하지 않습니다. 따라서 활성 표면적을 얻기 위해서는 전기화학적 분석을 세부적으로 수행해야 합니다.

XPS 분석은 C 1s을 조사하기 위해 수행되었습니다. , 3면d 및 Au 4f Au/VGCNF, Pd/VGCNF 및 PdAu/VGCNF 전기촉매 샘플에서. C 1s의 고해상도 피크 스펙트럼 피크는 그림 4a에 나와 있습니다. 284.6 eV(C-C), 285.4 eV(C-O-C), 286.6 eV(C-OH) 및 287.8 eV(C =O)의 4가지 구성 요소가 관찰되어 전기 촉매 샘플에서 VGCNF의 화학 구조를 결정할 수 있습니다. XPS는 Au/VGCNF, Pd/VGCNF 및 PdAu/VGCNF의 화학적, 전자적 상태 및 표면 조성을 특성화하는 데 사용되었습니다. 표 2는 Pd/VGCNF, Au/VGCNF 및 Pd₁의 중량 백분율 및 결합 에너지를 보여줍니다. 금₁ /VGCNF. 그림 4b는 지역 Au 4f를 나타냅니다. Au/C 및 PdAu/C의 스펙트럼. Au 4f에서 Au/VGCNF의 스펙트럼에서 이중 피크는 저에너지 대역을 포함합니다(Au 4f _7/2 ) 및 고에너지 대역(Au 4f _5/2 ) 84.1 및 87.7 eV에서 \( {\mathrm{AuCl}}_4^{2-} \) Au ⁰ 으로의 감소를 확인합니다. . Pd/VGCNF에 대한 그림 4c에서 피크는 335.4(Pd 3d _5/2 ) 및 340.7 eV(Pd 3d _3/2 )는 Pd 3d에 귀속됩니다. 이는 \( {\mathrm{PdCl}}_4^{2-} \)의 Pd ⁰ 으로의 감소를 확인합니다. . 한편, 바이메탈 PdAu/VGCNF의 경우 Au 4f 및 Pd 3d Au/VGCNF 및 Pd/VGCNF에 비해 낮은 각도로 약간 벗어납니다. 결합 에너지의 이동은 Pd에서 Au로의 전자 이동에 대한 강력한 정당성을 제공하며, 이는 아마도 Pd와 Au 원자 궤도 사이의 교란된 전자 상호 작용과 관련될 수 있고 합금 나노구조의 형성을 추가로 검증할 수 있습니다. Pd와 Au의 양은 피크 강도를 통해 확인할 수 있으며 Pd와 Au의 비율이 79:21로 계산된 값(50:50)보다 훨씬 높습니다. 이것은 Pd 원자가 촉매 표면의 바깥 부분에 풍부하다는 것을 의미합니다. 이는 Au(III)와 Pd(II)의 환원율 차이로 인해 발생합니다. Au 핵이 먼저 형성되고 핵에 Pd 원자가 추가되어 Pd가 풍부한 표면을 가진 합금 나노구조가 형성된다고 가정할 수 있습니다. 이 관찰은 Pd₁의 외부 표면에 금속성 Pd와 Au의 존재를 확인시켜줍니다. 금₁ /VCGNF 나노촉매 샘플.

Pd/VGCNF, Au/VGCNF 및 Pd₁의 고해상도 XPS 스펙트럼 금₁ /VGCNF. 아 페이지 4f _5/2 및 Pd 4f _7/2 . ㄴ Au 4f _5/2 및 Au 4f _7/2 및 c C 1s

기본 용액의 글리세롤 산화에 대한 전기화학 분석

촉매의 CV 스캔은 약 24시간 동안 유리질 탄소 전극에 촉매를 로딩한 후 수행되었습니다. 로딩 시간은 전류 밀도와 피크 전위(Ep)에 간접적으로 영향을 미칩니다. 로딩 시간이 증가함에 따라 샘플에서 방출된 수소의 총량에 더 많은 시간이 필요합니다. 전류 밀도는 수소 탈착과 관련된 개시 전위에서 엄청나게 증가합니다. The typical cyclic voltammetry curve in basic solution is generally used for the determination of hydrogen and oxygen adsorption on Pd/VGCNF, Au/VGCNF, and Pd₁ Au₁ /VGCNF in 0.5 M NaOH solution as depicted in Fig. 5. Region A in the potential range from − 0.8 to − 0.5 V can be assigned solely to adsorption and desorption of the H ⁺ ion on electrocatalyst surface area. However, the adsorption and desorption peaks cannot be clearly distinguished. This is possibly caused by the blocking of certain electrocatalyst active sites upon the incorporation of the second metal [33]. In region B, in the intermediate potential between − 0.4 V and − 0.2 V, the catalyst behaves as an ideally polarizable catalyst (double layer region) where the surface has free-adsorbed H ⁺ 그리고 오 ⁻ . Meanwhile, the formation of oxides occurs in the forward scan at the higher potential more than − 0.2 V between 0.1 and 0.3 V. The oxide reduction peak at − 0.34 V is also observed during the reverse scan in region C [33]. Meanwhile, Au/VGCNF electrocatalyst shows a slightly different voltammetry standard curve, where region A is the large capacitive current associated with the double layer region and is a typical electrochemical behavior of the Au catalyst followed by area B where the absorption of hydroxyl OH ⁻ species and oxide formation is at higher potential above − 0.2 V vs Ag/AgCl, while area C is observed as a reduction region of Au oxides.

Cyclic voltammogram for Pd/VGCNF, Au/VGCNF, and Pd₁ Au₁ /VGCNF in 0.5 M glycerol

Figure 6 shows the anodic peak current density for Au/VGCNF, Pd/VGCNF, and Pd₁ Au₁ /VGCNF electrocatalysts for the oxidation of glycerol in alkaline medium. The performance in cyclic voltammetry curve of the prepared electrocatalysts towards the oxidation of the glycerol is seen in terms of four parameters:(1) onset oxidation potential, (2) forward anodic peak potential, (3) forward anodic peak current, and (4) CO tolerance as can be seen in Table 1 are investigated. The oxidation peak in forward scan can be attributed to the oxidation of freshly chemisorbed species from glycerol adsorption, and the oxidation peak in negative scan means the removal of carbonaceous species incompletely oxidized the forward scan. As a result, the ratio of the forward current density peak (I _f ) to the backward current density peak (I _b ) reflects the tolerance ability to carbonaceous species accumulation. A high ratio I _f /나 _b indicates efficient oxidation of glycerol during the forward scan and little accumulation of carbonaceous residues. In terms of peak current density, Pd₁ Au₁ /VGCNF provided the best performance compared to Pd/VGCNF and Au/VGCNF. Besides that, Pd₁ Au₁ /VGCNF also shows the lowest onset potential (− 0.75 V vs.> − 0.60 for glycerol). The worst results were obtained with methanol, especially in terms of current density and oxidation overpotential. After a detailed perusal of the literature and estimating that the metal catalyst loading is very low (0.1 mg cm ⁻² ), one may readily realize that Pd₁ Au₁ /VGCNF can be classified among the most active electrocatalysts ever reported for the oxidation of glycerol in half-cells. The current density for glycerol oxidation with electrocatalysts Pd/C, Pt/C, and Au/C is significantly higher compared to Zhang et al. [26] due to higher catalyst loading and temperature dependence.

Cyclic voltammogram for Pd/VGCNF, Au/VGCNF, and PdAu/VGCNF in 0.5 M glycerol + 0.5 M NaOH

In Table 3, it exhibits that the bimetallic PdAu/VGCNF has high electrocatalytic activity towards the glycerol oxidation with respect to monometallic electrocatalyst. The presence of a second metal which is Au leads to a slight increase of the activity between 0.45 and 0.7 V versus Ag/AgCl, as higher current densities are achieved. Looking at CV curve (Fig. 6) recorded at Pd/VGCNF and Au/VGCNF electrocatalysts, both materials presented almost the same onset potential for the glycerol oxidation close to − 0.4 V vs Ag/AgCl. The onset potential for PdAu/VGCNF shifted towards a lower value due to the bifunctional mechanism which gives the catalytic improvement. In agreement with the bifunctional mechanism, Au is an oxyphilic material which has oxygen adsorbing character which promotes the chemisorbed species and assists the electrooxidation of glycerol leading to the decrease of the onset potential of glycerol electrooxidation and enhanced catalytic activity [34]. Besides that, bimetallic electrocatalysts PdAu/VGCNF also examined excellent CO tolerance, when the ratio I _f /나 _b is superior than others, which reveals the higher catalytic efficiency for direct oxidation during the forward scan.

Tafel Analysis

Figure 7a–c shows a Tafel plot of all the electrocatalysts tested in the reaction of the glycerol oxidation. Each Tafel plot shows two linear areas with an increase in Tafel slope. The Tafel slope is one of the kinetic parameters associated with the determination of a reaction that occurs on the surface of the electrode. At low oxidation potential (E_v ), the Tafel slope is low which indicates the kinetic transfer charge is fast during the reaction of the glycerol oxidation. At higher oxidation potential (E_v ), the value of the second Tafel slope is greater which indicates that the electrocatalytic reaction mechanism changes. The change in Tafel slope can be attributed to the kinetic rate of the charge transfer in the reaction decrease due to the presence of intermediate species which can poison the surface of the electrocatalysts (Kang et al. [35]).

Tafel slope for Au/VGCNF, Pd/VGCNF, and Pd₁ Au₁ /VGCNF electrocatalysts in solution (0.5 M NaOH + 0.5 M Glycerol) at scanning rate 50 mVs ^− 1

Table 4 lists the values of Tafel slope obtained on low and high potential oxidation. The Tafel slope for Pd₁ Au₁ /VGCNF electrocatalyst is lower than Pd/VGCNF and Au/VGCNF indicating that the charge transfer kinetic on bimetallic electrocatalyst is faster than single metal electrocatalyst for the glycerol oxidation reaction. Once the potential oxidation (E_v ) is increased, the Tafel slope also increased from low to high. This indicates that the reaction mechanism of the glycerol oxidation changes over the first one. Similar to the phenomenon occurring in other alcohol oxidation such as methanol [36] and ethanol [37], the maximum mass transfer of glycerol occurs in high potential oxidation (E_v ) which makes the hydroxyl adsorption and formed the oxide layer at electrocatalysts surface.

Performance of Au/VGCNF, Pd/VGCNF, and PdAu/VGCNF in Direct Glycerol Fuel Cell

Electrochemical I-V Characterization

Reliability of any synthesized electrocatalyst can generally be defined as the probability of the electrocatalyst to carry out its desired activity, which in this study is the catalysis for direct glycerol fuel cell applications. Although the electrocatalyst was analyzed earlier using a half-cell and showed good performance, the application of the electrocatalyst in direct glycerol fuel cells does not show outstanding performance. Figure 8 illustrates the cell polarization and power density curves of DGFC with FAA-3 (FuMA-Tech) membrane which show the passive DGFC single cell test results for Au/VGCNF, Pd/VGCNF, and Pd₁ Au₁ /VGCNF. From the DGFC performance test, results clearly show that the OCV and power density of Pd₁ Au₁ /VGCNF are higher compared to Pd/VGCNF and Au/VGCNF electrocatalysts. Table 5 lists the performance of all electrocatalysts in DGFC application in this study. In terms of electrocatalysts prices, roughly the price for Pd₁ Au₁ /VGCNF is USD 0.26/mg cheaper than the price for black Pd commercial which is USD 0.41/mg.

Polarization and power density curves for direct glycerol fuel cell (DGFCs) using PdAu/VGCNF at 25  ^° C

Passive-performance alkaline fuel cell may not be able to challenge the performance of the active fuel cell. One of the main problems for the passive alkaline fuel cell is related to the liquid electrolyte such as NaOH or KOH. This is due to the very spontaneous reaction with the NaOH electrolyte solution which is very sensitive to the presence of CO₂ from the air [38]. The use of air instead of oxygen will expose the hydroxyl ions to CO₂ contained in the air and will lead to the formation of Na₂ CO₃ or K₂ CO_3. The presence of carbonates will indirectly reduce the amount of OH ions in the anode and thereby reduce the ionic conductivity [39]. Too much carbonate will block the pores of the gas diffusion layer and can severely degrade the performance of the single cell [31,32,33] .

Electrochemical Impedance Spectroscopy

The performance of the direct glycerol fuel cell assessed by polarization curves does not reflect and give enough information about the condition of the inner component. Thus, electrochemical impedance spectroscopy (EIS) has to be carried out together with polarization curve measurements to evaluate the overall kinetic performance such as distinguishing the influences (voltage drop caused by charger transfer, membrane or mass transfer resistance) of the different processes (kinetic, ohmic, or mass transport dominated) in the whole electronic system [40]. Figure 9a–c shows the Nyquist plots which are one typical curve of electrochemical impedance spectroscopy (EIS) for three different types of electrocatalysts. Generally, the diameter of the semicircle arc is to measure the charge–transfer resistance for glycerol oxidation reactions. Apparently, the DIA in Fig. 9 showed the order as follows:Au/VGCNF > Pd/VGCNF > PdAu/VGCNF. This suggests that PdAu/VGCNF has the greatest charge transport performance, which was consistent with the abovementioned outstandingly excellent electrochemical catalytic activity. Besides that the equivalent circuit which was fit to EIS spectra shown in Fig. 9d in which Rs represents the solution resistance and Rct represents the charge–transfer resistance for the process of glycerol electrocatalytic oxidation. Overall, the Rct value for PdAu/VGCNF is much smaller compared to other electrocatalyst which reveals that the electron transfer for glycerol oxidation on PdAu/VGCNF is much easier, which could enhance the electrocatalytic activity of the electrocatalyst for glycerol oxidation.

Nyquist plots of electrochemistry impedance spectra for glycerol oxidation reaction of a Au/VGCNF, b Pd/VGCNF, c PdAu/VGCNF, and d circuit.

Since there is no difference in the MEA and cell assembly between the two cells, the lower resistance of PdAu/VGCNF cell can be attributed to the catalyst layer. In the PdAu/VGCNF-coated layer, small catalyst particle size can allow sufficient humidifying water to be held in the electrode and the uniform particle distribution can prevent the agglomeration effect, which may lead to the increasing boundary resistance. Furthermore, the small particle and uniform distribution can decrease the migration path of ions, which can further reduce the distributed resistance. The high-frequency EIS results provide the information that in the real fuel cell operation, the smaller cathode catalyst particle size will not only facilitate the ORR kinetics, but also reduce the performance loss that is due to the ohmic and contact resistances.

MEA Morphology Analysis

Basically, the low performance of the fuel cell may be due to the inherent properties of the materials used in fuel cell construction, defects in the materials, and the assembly process of the fuel cell. Below, we further discuss the potential effects that give rise to the lower performance of direct glycerol fuel cell.

Microporous Layer (MPL) Cracking

To justify the low performance of direct glycerol fuel cell, the morphology of some MEA were evaluated by SEM after the performance evaluation in the fuel cell. Figure 10a shows the typical SEM surface image for the microporous layer (MPL) consisting of the carbon black layer and the catalyst layer. Cracks were observed on the catalyst surface. The formation of wrinkles and cracks that occur in the MPL is likely due to a chemical reaction that cannot be controlled during the operation of single cell. This reaction probably causes dimensional changes in the polymer electrolyte membrane such as volume expansion and contraction that occur due to the hydrothermal stresses during the fuel cell operation [41]. Catalyst drying process occurs irregularly, causing cracks in the catalyst layer [42]. The fuel cell still can be operated in the presence of catalyst cracking. However, this indirectly degrades the fuel cell performance.

아 Delamination. ㄴ MPL cracking. ㄷ Catalyst agglomeration

Delamination

The SEM image presented in Fig. 10b clearly shows an obvious gap between the membrane and the electrodes after the operation of the direct glycerol fuel cell. This could be caused by the thermal expansion mismatch between the membrane and electrodes occurring during the operation of the fuel cell. In addition, this may also occur during the manufacturing process of the MEA such as owing to a too high temperature used during the catalyst layer drying process, which may form a vapor which will be trapped and thereby create an area where the adhesion between the two layers is poor [43]. Nevertheless, the electrolyte in the catalyst ink is expected to act as a binder during the lamination process. However, this may not occur in practice because the manual catalyst casting will lead to wrinkles on the electrode resulting in the existence of voids between the layers and subsequent degradation in the performance. Another reason for the gap in the interface may be the fact that mechanical hot pressing is difficult to ensure a fully intimate membrane–electrode interface. This is another factor which affects the fuel cell performance. This condition will increase the contact resistance and will require a longer time for the proton to travel to the catalyst sites and the existence of dead zone can occur which indirectly led to the loss of catalyst activity.

Orientation of Catalyst Layer

The catalyst layer was cast by manual casting. This method is difficult to control, and it has the potential to cause the agglomeration of undispersed catalyst powder [44, 45]. Figure 10c shows the areas corresponding to the agglomeration of nanoparticles on the MPL layer. This can create contact resistance over the entire MEA and therefore adversely impact the porosity or proton conductivity.

AEM Stability

The anion exchange membrane (AEM) shows some technological and scientific limitation. AEM suffers from a poor chemical stability in alkaline media arising from the hydroxide attack on the cationic group and resulting in the decreased anionic conductivity [46]. The AEM with OH ⁻ ion is less stable because AEM is easily converted to the less conductive \( {\mathrm{CO}}_3^{2-} \) and even less conductive \( {\mathrm{HCO}}_3^{-} \) forms when exposed to air even for short time. Figure 10d, e shows the comparison between before and after the treatment with alkali, indicating that AEM faced the problem of high swelling with the increased hydration [47]. This is a challenge in the handling of AEM. AEM is used to overcome the Nafion membrane degradation problem. However, AEM has a tendency to be hydrocarbon or aromatic based which gives rise to poor oxidation stabilities [41].