Recent advances in proton-conducting oxide electrolytes such as doped barium zirconates like BaCe1-xZrxY0.1Yb0.1O3-δ (i.e., BCZYYb) have opened a new pathway for steam electrolysis with solid electrolytes. The high proton-conductivity of BCZYYb enables operation at temperatures as low as 600°C (1), but typical water-splitting anodes such as Pr2NiO4+δ (PNO) have relatively high polarization resistances (around 0.15-0.20 W cm2 (2)). One postulate for the high resistance suggests poor electronic conductivity of PNO localizes the water-splitting reactions near the three-phase boundaries. To reduce polarization resistance, triple conducting anodes have been proposed (3). An alternative approach involves coating the anode surface with thin overlayers to improve electronic conductivity. To this end, our team is exploring electronically-conductive overlayers on PNO anodes to reduce polarization resistance. In this study, we have formulated thin-film (~300 nm) PNO anodes without and with thin (30-50 nm) BaZr0.7Y0.15Pr0.15O3-δ (BZYP) overlayers to assess the impact of these overlayers on improving anode surface electron conductivity and thereby extending the electrochemically active regions of the anode surface for water splitting.The patterned PNO single layers and PNO/BZYP bilayers are deposited on a 1.0 mm-thick BCZYYb electrolyte via Pulsed Laser Deposition (PLD) at room temperature and subsequently sintered at 1200ºC with independent Au current collectors (up to 6 on one electrolyte as in Figure 1). Conventional porous Ni/BCZYYb cathodes provide relatively low-resistance in comparison to the thin-film anodes such that the measured polarization resistance can be attributed to the anodes.In operando electrochemical impedance spectroscopy at temperatures from 550 to 700ºC and steam pressures ranging from 6 to 32 kPa show that the BZYP thin-films significantly reduce the bulk resistance and lower the polarization resistance by up to 20 %, as shown in Table 1. These results suggest that BZYP surface conductivity may cause extension of the electrochemically active region of the films away from the Au current collector. To explore this theory, a cell has been prepared with two thin-film electrodes for testing in an environmental x-ray photoelectron spectroscopy (E-XPS) system (Scienta Omicron). Initial exploration of the surface chemistry in steam environments in the single-gas chamber has identified signatures for various surface species associated with O2-, OH- and adsorbed H2O in accordance with past studies (4) as shown in Figure 2. Forthcoming in operando electrochemical tests in various H2O/O2 environments at temperatures up to 600ºC in the E-XPS will provide key evidence regarding the effectiveness of the BZYP overlayer at enhancing water splitting.References C. Duan, R.J. Kee, H.Y. Zhu, C. Karakaya, Y.C. Chen, S. Ricote, A. Jarry, E.J. Crumlin, D. Hook, R. Braun, N.P. Sullivan, and R. O'Hayre, Nature, 557(7704), 217-+ (2018).W.Y. Li, B. Guan, L. Ma, S.S. Hu, N. Zhang, and X.B. Liu, Journal of Materials Chemistry A, 6(37), 18057-18066 (2018).H.C. Tian, W.Y. Li, L. Ma, T. Yang, B. Guan, W.Y. Shi, T.L. Kalapos, and X.B. Liu, Acs Applied Materials & Interfaces, 12(44), 49574-49585 (2020).A. Jarry, G.S. Jackson, E.J. Crumlin, B. Eichhorn, and S. Ricote, Physical Chemistry Chemical Physics, 22(1), 136-143 (2020). Figure 1