In view of high catalytic activity and oxygen vacancy concentration, Ruddlesden−Popper (R-P) structure oxide has been widely used as the electrode material for solid oxide fuel cells (SOFCs). Herein, three R-P structure oxides, Pr 2−x Sr x Ni 0.2 Mn 0.8 O 4 (x = 1, 1.2, and 1.5), are used as the semiconductor materials of single-component cells. The materials for the oxygen side are hybrid oxides consisting of R-P structure oxide and perovskite oxide. The hydrogen side was exposed to the reduction atmosphere before the test, and the perovskite structure disappeared and the lattice parameters of the R-P structure changed, resulting in the formation of a new R-P structure and MnO 2 or NiMn alloy. In addition, Pr 0.5 Sr 1.5 Ni 0.2 Mn 0.8 O 4 and reduced Pr 0.5 Sr 1.5 Ni 0.2 Mn 0.8 O 4 exhibit the most content of oxygen vacancy. For a single-component fuel cell (SCFC), the cell performance increased with the decrease in Pr content. The SCFC composed of Pr 0.5 Sr 1.5 Ni 0.2 Mn 0.8 O 4 shows the highest maximum power densities (P max ), which reached 206.6 mW cm −2 at 700 °C. It is because the reduced Pr 0.5 Sr 1.5 Ni 0.2 Mn 0.8 O 4 has the highest catalytic activity for hydrogen oxidation reaction (HOR). Furthermore, the P max at 700 °C can reach a value of 198.1 mW cm −2 in SOFC mode, and in the case of SOEC mode, the current density at 700 °C is as high as −390.8 mA cm −2 with an applied electrolysis voltage of 1.3 V for the reversible single-component cell (RSCC) with Pr 0.5 Sr 1.5 Ni 0.2 Mn 0.8 O 4 as the semiconducting electrocatalyst.

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Doping different cations into the B-sites of perovskite oxides is often used to increase the concentration of oxygen vacancy (V o ••), further enhancing their electrocatalytic activity. In this work, Pr0.4Sr0.5Co0.45Fe0.45Mo0.1O3 (PSCFM11), Pr0.4Sr0.5Co0.2Fe0.7Mo0.1O3 (PSCFM27), and Pr0.4Sr0.5Ni0.2Fe0.7Mo0.1O3 (PSNFM27) are synthesized and used as semiconductor materials for the reversible single-component cell (RSCC). In the hydrogen electrode side of the cell, PSCFM11, PSCFM27, and PSNFM27 can be reduced and in situ precipitate Co–Fe alloy and Ni–Fe alloy, and the reduced PSNFM27 exhibits the highest concentration of V o ••. The single-component fuel cell (SCFC) composed of PSNFM27 and reduced PSNFM27 shows the best cell performance, and the maximum power density is 328.6 mW cm–2 at 700 °C, indicating the higher concentration of V o •• and the higher catalytic activity toward the hydrogen oxidation reaction (HOR). In addition, the RSCC composed of PSNFM27 and reduced PSNFM27 shows the best discharge and water electrolysis performance. The maximum power density of the RSCC can reach 315.3 mW cm–2, and the electrolysis current density at 1.3V is −612.7 mA cm–2 at 700 °C.

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