Encapsulated Co–Ni alloy boosts high-temperature CO2 electroreduction

Summary

Chemicals and materialsNickel(II) nitrate hexahydrate (Ni(NO3)2·6H2O, 99.9%, ABCR), manganese(II) nitrate hexahydrate (Mn(NO3)2·6H2O, 98%, ABCR), iron(III) nitrate nonahydrate (Fe(NO3)3·9H2O, 98%, ABCR), cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O, 98+%, ABCR), copper(II) nitrate trihydrate (Cu(NO3)2·3H2O, 98+%, Sigma), ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24 ·4H2O, 99%, Roth), indium(III) nitrate hydrate (In(NO3)3·H2O, 99.9%, Sigma), tin(II) chloride (SnCl2, 98%, Sigma), citric acid (99.5%, Acros), ethylene glycol (99+%, Brunschwig), cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O, 99.5%, ABCR), samarium(III) nitrate hexahydrate (Sm(NO3)3·6H2O, 99.9%, ABCR), ethylenediaminetetraacetic acid (99%, IVALUA), ammonia solution (25%, VWR), lanthanum(III) nitrate hexahydrate (La(NO3)3·6H2O, 99.9%, ABCR), strontium nitrate (Sr(NO3)2, 99+%, Fisher), LSGM (99%, Sigma), copper(II) oxide (CuO, 99%, Sigma), dispersant (2%, Fiaxell SOFC Technologies), binder (30%, Fiaxell SOFC Technologies) and carbon dioxide (CO2, 99.9%, Carbagas) were all used as received without further purification.Synthesis of MxNi1−x@SDCMxNi1−x@SDC was synthesized using a sol–gel method. First, 20 mmol of Ni(NO3)2·6H2O and 20 mmol of a second metal salt, which included Mn(NO3)2·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Cu(NO3)2·3H2O, Zn(NO3)2·6H2O, (NH4)6Mo7O24·4H2O, In(NO3)3·H2O or SnCl2, were dissolved in 50 ml of H2O at 100 °C under vigorous stirring. Then, 100 mmol of citric acid and 100 mmol ethylene glycol were added to the solution to form a sol. Subsequently, 8 mmol of Ce(NO3)3·6H2O and 2 mmol of Sm(NO3)3·6H2O were added. The reaction was kept at 100 °C for about 3 h to evaporate H2O from the system. The remaining solvent was removed at 300 °C overnight in an oven, followed by heat treatment in air at 600 °C for 5 h with a ramping rate of 5 °C min−1. By changing the feeding molar ratio of Ni(NO3)2·6H2O and Co(NO3)2·6H2O while keeping their total amounts to 40 mmol, we obtained CoxNi1−x@SDC cat...