fig4

Figure 4. (A) Illustration of conventional anode/electrolyte/cathode SOFC from a physical-electrochemical view as a p-i-n structure. (B) A p-n junction double layer device from removing the ionic electrolyte layer. (C) A single-layer device based on the nano-redox reaction principle with a bulk p-n heterojunction and energy band alignment (CC). Schematic diagram of nano-redox reaction mechanisms based on (D) O^2- and H⁺, (E) O and H⁺ and (F) O^2- and H, respectively. Copyright from 2013 Nano Energy, including the text from (A), (B) and (C). CC: Current collector; CB: conduction band; VB: valence band; LSM: La_0.85Sr_0.15MnO₃; YSZ: yttria-stabilized zirconia; HOR: hydrogen oxidation reaction; ORR: oxygen reduction reaction; SDC: samarium-doped ceria.