Trends in high-temperature H2 production on CeO2 Co-doped with trivalent cations in solid oxide electrolysis cells

Abstract

CeO2-based catalysts incorporated with cooperative dopants show excellent potential for promoting H2 production via the water-splitting reaction (WSR) in solid oxide electrolysis cells (SOECs). Here, we report that CeO2 co-doped with Gd + Sb, Pr + Sb, and Bi + Sb trivalent cations have superior performance for WSR with the reaction rate 2–5 orders of magnitude larger than that of individual trivalent dopants including Ga, Sb, Lu, Gd, Sm, Pr, Bi, and La, owing to improved stability of hydridic H-species and accordingly decreased barrier for their decompositions into H2 by co-doping. The energy of hydridic H-species and the turn-over frequency (TOF) toward H2 production is shown to correlate well with the average ionic radius of trivalent cations, where the TOF increases with decreasing ionic radius and Gd + Sb, Pr + Sb, and Bi + Sb with smaller ionic radius show better WSR activity than other dopants. Our studies suggest incorporating ceria with proper co-dopants with an average radius close to Gd + Sb, Pr + Sb, or Bi + Sb pairs as an effective strategy for enhancing WSR performance on CeO2 in SOECs.