## 3 Results and Discussion  
Firstly, the mole fraction of H\({}_{2}\) in the anode side is shown in Figure 4a. Fuels are fed over the porous anode surface through the input rib channels. Then, they will be transported to the anode-electrolyte interface through the porous anode. In these reaction sites, most of the fuel will be consumed. Then, the unused fuel and vapor produced will be transported to the exhaust rib channels as shown in Figure 2. Thus, we can get that the H\({}_{2}\) mole fraction in the 20 input rib channels is larger than that in the 19 exhaust rib channels. Similarly, Figure 4b shows the H\({}_{2}\)O mole fraction distribution among the total 39 rib channels. Obviously, the H\({}_{2}\)O mole fractions in the 19 exhaust rib channels are larger than that in the 20 input rib channels. From this result, we can get that using the interdigitated design for rib channels of the fuel flow path is good for managing the H\({}_{2}\) and vapor flows. H\({}_{2}\) will be fed over the porous anode by the input rib channels, and most of the production (i.e., vapor) will be collected by the exhaust rib channels directly. This conclusion is similar to that in the PEMFC cathode as reported by [PERSON] et al. [27]. To further get the H\({}_{2}\) and H\({}_{2}\)O transporting qualities within the porous anode for the interdigitated design, Figure 5a,b show the H\({}_{2}\) and H\({}_{2}\)O mole fraction distribution features over the anode-electrolyte interface, respectively. As the support layer of the current SOFC is a porous anode, H\({}_{2}\) can fully diffuse into the porous anode with relatively low resistance. This makes the distribution of the H\({}_{2}\) mole fraction over the anode-electrolyte interface (vertical to the fuel flow direction) more uniform (as Figure 5a). Obviously, the H\({}_{2}\) transport within the interdigitated design can be enhanced compared to other designs because of the rising static pressure within the input rib channels. A similar result for the molar fraction distribution of H\({}_{2}\)O in Figure 5b also illustrates well the vapor transporting capability within the porous anode, while the SOFC stack adopts an interdigitated design for the fuel flow path. Figure 4: Mole fractions of fuel within the anode side: (**a**) H2, (**b**) vapor. (note: e-01 in the figure means \(\times\) 10\({}^{-1}\)). Figure 5: Mole fraction distributions over the anode–electrolyte interface: (**a**) H\({}_{2}\); (**b**) H\({}_{2}\)O. (note: e-01 in the figure means \(\times\) 10\({}^{-1}\)). Figure 6 shows the oxygen mole fraction distribution characteristic within the cathode air flow path. Obviously, the O\({}_{2}\) mole fraction within the rib channels will decrease along the air flow direction. However, the mole fraction changes are relatively small due to the conventional line-type configuration of the rib channels and high air flow supply rate of the stack. Different from the PEMFC stack case, the vapor is produced on the anode side of the SOFC stack. For the SOFC stack, the air flow will not only act as the reactant, it will also act as the main heat transfer carrier. Thus, the high air flow supply rate of the SOFC stack and the large molecular mass determine that a low flow resistance flow path is recommended. Thus, different from the PEMFC case, an interdigitated design is not a good choice for the air flow path in the SOFC stack, based on the above described three factors. Generally, the temperature gradient within the stack would greatly affect the performance and durability of the SOFC stack. Figure 7 shows the overall temperature distribution within the one-cell SOFC stack. It shows that the rib channel temperature change at the H\({}_{2}\) inlet side is higher than the other channels. The temperature rises instantly when H\({}_{2}\) enters the channels, almost reaching the maximum temperature of the stack. On the other hand, the temperature of the air inlet side of the cell changes more uniformly.