The entropy increase strategy of BaZr0.1Ce0.7Y0.2O3-δ (BZCY) proton-conducting electrolytes by doping Dy to enhance the chemical stability against CO2 and H2O

Medium-entropy BaZr 0.1 Ce 0.5 Y 0.2 Dy 0.2 O 3-δ (BZCYD) electrolytes with a configurational entropy of 1.22 R are prepared by doping Dy element into low-entropy BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ ( BZCY, 0.80 R). The entropy increasing strategy makes dramatically contribution to the improved chemical stability against CO 2 and H 2 O, and the relevant mechanism is clarified by the density functional theory (DFT). The BZCYD electrolyte shows stable phase composition and micro-structure after CO 2 heat treatment at 700 °C for 3 h and H 2 O treatment boiled for 3 h, while generation of impurities of BaCO 3 and Ba(OH) 2 accompanied by destroyed micro-structure are formed in the BZCY electrolyte under the same conditions. The total conductivity decay rates of BZCYD electrolyte after CO 2 heat treatment and H 2 O treatment are 44.1 % and 52.5 %, respectively, which exhibit significantly better than those of BZCY electrolyte (88 % and 74 %). According to the first-principles calculation, BZCYD electrolyte has higher CO 2 reaction energy barrier (5.21 eV) and H 2 O reaction energy barrier (7.30 eV), as well as lower CO 2 adsorption energy (−5.182 eV) and H 2 O adsorption energy (−0.742 eV), so it has better chemical stability. The peak power density of the anode-supported single cell with BZCYD electrolyte is 510 mW cm −2  at 700 °C in humid H 2 .