# Perspectives on Cathodes for Protonic Ceramic Fuel Cells
## 5 Composite Cathodes
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Air Electrode** & **ASR (f-cm2)** & **MPD (W-cm2)** & **Electrolyte** & **Thickness (\(\upmu\)m)** & **Ref** \\ \hline \multicolumn{5}{c}{Mixed proton–electron-conducting cathodes} \\ \hline BaCe\({}_{0.1}\)Zr\({}_{0.2}\)Y\({}_{0.1}\)Fe\({}_{0.6}\)O\({}_{3-5}\) & 0.21 (700 \({}^{\circ}\)C) & 0.240 (700 \({}^{\circ}\)C) & BCZYYb7111 & 30 & [33] \\ \hline BaCe\({}_{0.9}\)Y\({}_{\rm Pry}\)Gd\({}_{1}\)O\({}_{3-\delta}\) & 0.47 (800 \({}^{\circ}\)C) & - & BCG20 & 510 & [21] \\ \hline BaPt\({}_{0.8}\)In\({}_{0.2}\)O\({}_{3-\delta}\) & 0.09 (700 \({}^{\circ}\)C) & 0.550 (700 \({}^{\circ}\)C) & BCZYYb7111 & 15 & [25] \\ \hline BaZr\({}_{0.2}\)Fe\({}_{0.6}\)O\({}_{3}\)O\({}_{3-\delta}\) & 0.28 (700 \({}^{\circ}\)C) & 0.322 (700 \({}^{\circ}\)C) & BCZY71 & 20 & [32] \\ \hline BaZr\({}_{0.6}\)Co\({}_{0.4}\)O\({}_{3-\delta}\) & 0.19 (700 \({}^{\circ}\)C) & - & BCZY53 & 20 & [31] \\ \hline \multicolumn{5}{c}{Mixed oxide–ion–electron-conducting cathodes} \\ \hline Ba\({}_{0.5}\)La\({}_{0.5}\)CoO\({}_{3}\) & 1.4 (600 \({}^{\circ}\)C) & - & Ba(Zr\({}_{0.5}\)Ce\({}_{0.4}\))\({}_{8/9}\)Y\({}_{0.2}\)O\({}_{3-\delta}\) & 12 & [45]  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Air Electrode** & **ASR (\(\Omega\)-cm\({}^{2}\))** & **MPD (W-cm\({}^{-2}\))** & **Electrolyte** & **Thickness (\(\mu\)m)** & **Ref** \\ \hline La\({}_{1.5}\)Ca\({}_{0.5}\)NiO\({}_{4-5}\) & 0.05 (700 \({}^{\circ}\)C) & 0.923 (700 \({}^{\circ}\)C) & BCZY71 & 15 & [87] \\ \hline La\({}_{2}\)Ni\({}_{1.6}\)Fe\({}_{04}\)O\({}_{7}\) & 0.15 (700 \({}^{\circ}\)C) & 0.398 (700 \({}^{\circ}\)C) & BCZY53 & 20 & [88] \\ \hline LaBaCuCoCo\({}_{8-x}\) & 0.15 (700 \({}^{\circ}\)C) & 0.432 (700 \({}^{\circ}\)C) & BCZY71 & 20 & [97] \\ \hline LaBaCuFeO\({}_{5+x}\) & 0.27 (700 \({}^{\circ}\)C) & 0.327 (700 \({}^{\circ}\)C) & BCZY71 & 20 & [97] \\ \hline LaNi\({}_{0.6}\)Fe\({}_{04}\)O\({}_{3-\delta}\) & 0.13 (700 \({}^{\circ}\)C) & 0.550 (700 \({}^{\circ}\)C) & BCZY71 & 15 & [90] \\ \hline LiNi\({}_{0.8}\)Co\({}_{2}\)O\({}_{2}\) & 3.48 (650 \({}^{\circ}\)C) & 0.410 (650 \({}^{\circ}\)C) & BCZY71 & 24 & [92] \\ \hline NBSCF & 0.08 (700 \({}^{\circ}\)C) & 1.370 (700 \({}^{\circ}\)C) & BCZYvb7111 & 14.7 & [98] \\ \hline Nd\({}_{2}\)NiO\({}_{4-\delta}\) & 4.8 (600 \({}^{\circ}\)C) & 0.060 (600 \({}^{\circ}\)C) & BCY10 & 25 & [79] \\ \hline PBSCF & 0.13 (600 \({}^{\circ}\)C) & 0.500 (500 \({}^{\circ}\)C) & BCZYvb4411 & 15 & [101] \\ \hline PBSCF & 0.30 (600 \({}^{\circ}\)C) & 0.650 (600 \({}^{\circ}\)C) & BCZYYb6211 & 7.6 & [103] \\ \hline PBSCF & - & 1.100 (650 \({}^{\circ}\)C) & BCZYvb4411 & 15 & [102] \\ \hline Pr\({}_{2}\)BaNiMnO\({}_{7-\delta}\) & 0.084 (700 \({}^{\circ}\)C) & 1.070 (700 \({}^{\circ}\)C) & BCZYvb7111 & 20 & [108] \\ \hline Pr\({}_{2}\)NiO\({}_{4-\delta}\) & 0.70 (650 \({}^{\circ}\)C) & 0.130 (650 \({}^{\circ}\)C) & BCY10 & 85 & [77] \\ \hline Pr\({}_{2}\)NiO\({}_{4-\delta}\) & 0.06 (650 \({}^{\circ}\)C) & 0.820 (650 \({}^{\circ}\)C) & BaCo\({}_{0.58}\)Zn\({}_{0.3}\)Y\({}_{0.15}\)O\({}_{3-\delta}\) & 5 & [82] \\ \hline (PrB\({}_{0.8}\)Ca\({}_{0.2}\)O\({}_{0.95}\)Co\({}_{2}\)O\({}_{6-\delta}\) & 0.14 (600 \({}^{\circ}\)C) & 0.540 (600 \({}^{\circ}\)C) & BCZYvb6211 & 20 & [105] \\ \hline PrNi\({}_{0.5}\)Co\({}_{0.5}\)O\({}_{3-\delta}\) & 0.05 (500 \({}^{\circ}\)C) & 0.611 (600 \({}^{\circ}\)C) & BCZYvb4411 & 10 & [114] \\ \hline SmBa\({}_{0.5}\)Sr\({}_{0.5}\)Co\({}_{2}\)O\({}_{5+\delta}\) & 0.08 (700 \({}^{\circ}\)C) & 0.533 (700 \({}^{\circ}\)C) & BCZY71 & 15 & [97] \\ \hline SmBaCo\({}_{2}\)O\({}_{5+\delta}\) & 0.15 (700 \({}^{\circ}\)C) & 0.382 (700 \({}^{\circ}\)C) & BCZY71 & 25 & [95] \\ \hline Sr\({}_{2}\)Fe\({}_{1.5}\)MoO\({}_{4.2}\)r\({}_{0.1}\)O\({}_{6-\delta}\) & 0.17 (700 \({}^{\circ}\)C) & 0.790 (700 \({}^{\circ}\)C) & BCZYvb7111 & 20 & [159] \\ \hline Sr\({}_{2}\)Sc\({}_{0.1}\)Nb\({}_{0.1}\)Co\({}_{1.5}\)Fe\({}_{0.3}\)O\({}_{6-\delta}\) & 0.14 (650 \({}^{\circ}\)C) & 0.840 (650 \({}^{\circ}\)C) & BCZYvb7111 & 18.5 & [106] \\ \hline \multicolumn{5}{c}{Composite cathodes} \\ \hline Ba\({}_{0.4}\)K\({}_{0.1}\)Sr\({}_{0.5}\)Co\({}_{0.8}\)Fe\({}_{0.2}\)O\({}_{3-\delta}\): & 0.05 (700 \({}^{\circ}\)C) & 1.275 (750 \({}^{\circ}\)C) & BCZY71 & 10 & [152] \\ BCZY71 & & & & & \\ \hline Ba\({}_{0.95}\)Ca\({}_{0.05}\)Fe\({}_{0.8}\)5\({}_{0.05}\)Sr\({}_{0.0.5}\)Y\({}_{0.1}\)O\({}_{3-\delta}\): & 0.05 (700 \({}^{\circ}\)C) & 0.950 (700 \({}^{\circ}\)C) & BCZY71 & 17 & [171] \\ \hline Ba\({}_{0.95}\)La\({}_{0.1}\)Fe\({}_{0.95}\)Zn\({}_{0.2}\)O\({}_{3-\delta}\): BCZY71 & 0.08 (750 \({}^{\circ}\)C) & 0.330 (750 \({}^{\circ}\)C) & BCZYYb7111 & 42 & [197] \\ \hline Ba\({}_{0.9}\)Co\({}_{0.4}\)Fe\({}_{0.4}\)Zr\({}_{0.1}\)Y\({}_{0.1}\)O\({}_{3-\delta}\): & 0.15 (700 \({}^{\circ}\)C) & 0.540 (700 \({}^{\circ}\)C) & BCZY71 & 25 & [196] \\ \hline Ba\({}_{0.9}\)Sr\({}_{0.9}\)Zr\({}_{0.9}\)Zr\({}_{0.2}\)O\({}_{3-\delta}\) & 0.20 (600 \({}^{\circ}\)C) & 0.197 (600 \({}^{\circ}\)C) & BCY10 & 60 & [139] \\ \hline BaCo\({}_{0.4}\)Fe\({}_{0.4}\)Co\({}_{0.2}\)O\({}_{3-\delta}\) & 0.075 (700 \({}^{\circ}\)C) & 0.335 (700 \({}^{\circ}\)C) & BCZYvb7111 & 70 & [169] \\ \hline BaCo\({}_{0.4}\)Fe\({}_{0.4}\)Zr\({}_{0.1}\)Y\({}_{0.1}\)Y\({}_{0.1}\)O\({}_{3-\delta}\): & 0.25 (600 \({}^{\circ}\)C) & 0.660 (600 \({}^{\circ}\)C) & BCZYvb7111 & 10-20 & [153] \\ \hline BSCF: BCY10 & 0.53 (600 \({}^{\circ}\)C) & 0.293 (700 \({}^{\circ}\)C) & BCY10 & 15 & [149] \\ \hline BSCF: BCZY71 & 0.10 (700 \({}^{\circ}\)C) &  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Air Electrode** & **ASR (\(\Omega\)-cm\({}^{2}\))** & **MPD (W-cm\({}^{2}\))** & **Electrolyte** & **Thickness (\(\mu\)m)** & **Ref** \\ \hline LaCoO\({}_{3}\): BCZY27 & 0.11 (600 \({}^{\circ}\)C) & - & BCZY27 & - & [138] \\ \hline LSCF: BaCe\({}_{0.52}\)Zr\({}_{0.35}\)Y\({}_{0.15}\)O\({}_{3-\delta}\) & 0.18 (700 \({}^{\circ}\)C) & 0.537 (700 \({}^{\circ}\)C) & BaCe\({}_{0.52}\)Zr\({}_{0.35}\)Y\({}_{0.15}\)O\({}_{3-\delta}\) & 8 & [145] \\ \hline LSCF: BCYb10 & 0.14 (700 \({}^{\circ}\)C) & 0.050 (700 \({}^{\circ}\)C) & BCY20 & 15-20 & [143] \\ \hline LSCF: BCY10 & 0.49 (600 \({}^{\circ}\)C) & - & BZY20 & - & [144] \\ \hline LSF73: 20 SDC & 0.074 (650 \({}^{\circ}\)C) & 0.542 (650 \({}^{\circ}\)C) & BCZY71 & 13 & [163] \\ \hline LSF73: BCZY71 & 0.13 (700 \({}^{\circ}\)C) & 0.450 (700 \({}^{\circ}\)C) & BCZY71 & 15 & [162] \\ \hline LSR82: Ba(Ce\({}_{0.51}\)Zr\({}_{0.30}\)Y\({}_{0.15}\)Zr\({}_{0.04}\))O\({}_{3-\delta}\) & 0.09 (700 \({}^{\circ}\)C) & 0.425 (700 \({}^{\circ}\)C) & Ba(Ce\({}_{0.51}\)Zr\({}_{0.30}\)Y\({}_{0.15}\) & \\  & & & Zn\({}_{0.04}\)O\({}_{3-\delta}\) & 70 & [156] \\ \hline LSM82: La\({}_{0.995}\)Ca\({}_{0.005}\)NbO\({}_{4}\) & 25 (750 \({}^{\circ}\)C) & - & La\({}_{0.995}\)Ca\({}_{0.005}\)NbO\({}_{4}\) & - & [174] \\ \hline LSM82: La\({}_{5.5}\)WO\({}_{12-\delta}\) & 8 (750 \({}^{\circ}\)C) & - & La\({}_{5.5}\)WO\({}_{12.5}\) & - & [175] \\ \hline LSM82: BCY15 & 0.11 (750 \({}^{\circ}\)C) & 0.394 (750 \({}^{\circ}\)C) & BCY15 & 15 & [178] \\ \hline LSM82: La\({}_{5.5}\)WO\({}_{11.25-\delta}\): 20 SDC & 1.4 (750 \({}^{\circ}\)C) & - & La\({}_{5.5}\)WO\({}_{11.25-\delta}\) & - & [176] \\ \hline LSM82: La\({}_{28.8}\)W\({}_{4.4\alpha}\)O\({}_{34.38/2}\) & 40 (650 \({}^{\circ}\)C) & - & La\({}_{28.8}\)W\({}_{4.\alpha}\)O\({}_{34.38/2}\) & - & [177] \\ \hline LSM82: 50 LDC & 0.69 (800 \({}^{\circ}\)C) & 0.065 (800 \({}^{\circ}\)C) & La\({}_{0.995}\)Ca\({}_{0.01}\)NbO\({}_{4}\) & 20 & [173] \\ \hline LSM82: BCZY71: Pr & 0.33 (700 \({}^{\circ}\)C) & & BCZY71 & - & [180] \\ \hline Nd(Ba\({}_{0.75}\)Ca\({}_{0.25}\)) & & 0.091 (650 \({}^{\circ}\)C) & 0.880 (650 \({}^{\circ}\)C) & BCZYb7111 & 20 & [191] \\ \hline Nd\({}_{0.5}\)Ba\({}_{0.5}\)Fe\({}_{0.30}\)Ni\({}_{0.1}\)O\({}_{3-\delta}\): BCZY71 & 0.15 (700 \({}^{\circ}\)C) & 0.490 (700 \({}^{\circ}\)C) & BCZY71 & 40 & [151] \\ \hline Nd\({}_{0.5}\)Ba\({}_{0.5}\)Fe\({}_{0.30}\)Ni\({}_{0.1}\)O\({}_{3-\delta}\): BCZY71 & 0.15 (700 \({}^{\circ}\)C) & 0.490 (700 \({}^{\circ}\)C) & BCZY71 & 40 & [168] \\ \hline Nd\({}_{0.5}\)Ni\({}_{0.4-\delta}\): BCZYYb711 & 0.43 (750 \({}^{\circ}\)C) & 0.154 (750 \({}^{\circ}\)C) & BCZYYb7111 & 60 & [182] \\ \hline Nd\({}_{0.5}\)Sr\({}_{0.5}\)Co\({}_{1.5}\)Fe\({}_{0.5}\)O\({}_{5-\delta}\): & 0.18 (650 \({}^{\circ}\)C) & 0.719 (650 \({}^{\circ}\)C) & BCZYYb7111 & 20 & [190] \\ \hline PBCO: BCZY71: 10 GDC & 0.05 (700 \({}^{\circ}\)C) & 1.020 (700 \({}^{\circ}\)C) & BCZY71 & 12 & [199] \\ \hline PBCO: BCZYYb7111 & 0.08 (750 \({}^{\circ}\)C) & 0.490 (750 \({}^{\circ}\)C) & BCZYYb7111 & 30 & [193] \\ \hline Pr\({}_{0.58}\)Sr\({}_{0.4}\)Fe\({}_{0.5}\)Co\({}_{0.2}\)O\({}_{3-\delta}\): BCYb10 & 0.50 (700 \({}^{\circ}\)C) & - & BCYbb10 & 20 & [167] \\ \hline Pr\({}_{0.58}\)Sr\({}_{0.4}\)Cu\({}_{0.2}\)Fe\({}_{0.5}\)O\({}_{3-\delta}\): 20 SDC & 0.14 (650 \({}^{\circ}\)C) & 0.456 (650 \({}^{\circ}\)C) & BCZY53 & 20 & [165] \\ \hline Pr\({}_{0.5}\)Sr\({}_{0.4}\)Cu\({}_{0.2}\)Fe\({}_{0.5}\)O\({}_{3-\delta}\): 20 SDC & - & 0.556 (650 \({}^{\circ}\)C) & BCZY71 & 14 & [165] \\ \hline Pr\({}_{0.5}\)La\({}_{0.1}\))(Ni\({}_{0.74}\)Cu\({}_{0.2}\)Ni\({}_{0.05}\)) & 0.13 (700 \({}^{\circ}\)C) & 0.770 (700 \({}^{\circ}\)C) & BCZY71 & 12 & [184] \\ \hline Pr\({}_{1.7}\)Ca\({}_{0.3}\)NiO\({}_{4+\delta}\): BaCe\({}_{0.5}\)Gd\({}_{0.15}\)Cu\({}_{0.01}\)O\({}_{3-\delta}\) & 0.26 (700 \({}^{\circ}\)C) & 0.170 (700 \({}^{\circ}\)C) & BaCe\({}_{0.8}\)Gd\({}_{0.19}\)Cu\({}_{0.01}\)O\({}_{3-\delta}\) & 25 & [188] \\ \hline Pr\({}_{1.9}\)Ba\({}_{0.1}\)NiO\({}_{4-\delta}\): BaCe\({}_{0.5}\)Zr\({}_{0.3}\)Dy\({}_{0.2}\)O\({}_{3-\delta}\) & 0.43 (700 \({}^{\circ}\)C) & 0.470 (700 \({}^{\circ}\)C) & BaCe\({}_{0.5}\)Zr\({}_{0.3}\)Dy\({}_{0.2}\)O\({}_{3-\delta}\) & 30 & [185] \\ \hline Pr\({}_{2}\)NiO\({}_{4}\): BCZY62