First insights for hydrogen production using an alkaline ceramic through the water-gas shift reaction

Abstract

• Li 2 CuO 2 was analyzed as multifunctional material in the WGSR. • In the C-WGSR, H 2 production was obtained in a short time range. • The best H 2 production was obtained between 200 and 250 °C in the S-WGSR. • Li 2 CuO 2 acts as hydroxide source, catalyst and/or CO 2 captor. • A high Li 2 CuO 2 regeneration was obtained under O 2 at 700 °C. Hydrogen production was successfully obtained and enriched using lithium cuprate (Li 2 CuO 2 ) as a multifunctional material during the water-gas shift reaction (WGSR). For this propose, water vapor and carbon monoxide reacted consecutively (C-WGSR) or simultaneously (S-WGSR) over the Li 2 CuO 2 particle surface. In both cases, Li 2 CuO 2 functioned as a catalyst, producing H 2 and CO 2 in a moderate temperature range (250–450 °C). In addition, lithium cuprate was able to capture the CO 2 produced in WGSR, enhancing the H 2 purity in the final gas flow. When the consecutive procedure (C-WGSR, first water vapor and then CO) was employee, the best H 2 formation (75%) was obtained at around 250 °C. However, it was limited by the amount of H 2 O previously sorbed on Li 2 CuO 2 surface, proceeding the reaction only in a short period of time (t < 1 min). In the second case S-WGSR, H 2 O vapor and CO were flowed simultaneously at 300 °C, resulting in lower amounts of H 2 (between 30 and 50 %) than in C-WGSR. However, hydrogen production was maintained for longer times (0 < t < 120 min), presenting an important advantage over the consecutive procedure. It must be mentioned that in S-WGSR, the CO 2 chemisorption on the ceramic tended to diminish the H 2 production as Li 2 CO 3 produced through the capture process blocking the H 2 O sorption sites, although the CO continued being totally converted. Further cyclic experiments showed that it was possible to maintain H 2 formation during several consecutive cycles when lithium cuprate regeneration was performed under an oxygen flow at 700 °C. Finally, this work is the first experimental evidence that an alkaline ceramic can act as a functional material to produce a clean energy source, such as hydrogen through the WGSR process at low and moderate temperatures.