Riaz Asim, Lipiński Wojciech, Lowe Adrian
Research School of Electrical, Energy and Materials Engineering, The Australian National University Canberra ACT 2601 Australia
RSC Adv. 2021 Jul 1;11(37):23095-23104. doi: 10.1039/d1ra02234b. eCollection 2021 Jun 25.
Synthesis gas production solar thermochemical reduction-oxidation reactions is a promising pathway towards sustainable carbon-neutral fuels. The redox capability of oxygen carriers with considerable thermal and chemical stability is highly desirable. In this study, we report Ce-doped VO structures for high-temperature thermochemical-looping reforming of methane coupled to HO and CO splitting reactions. Incorporation of fractional amounts of large cerium cations induces a V to V transition and partially forms a segregated CeVO phase. More importantly, the effective combination of efficient ion mobility of cerium and high oxygen exchange capacity of vanadia achieves synergic and cyclable redox performance during the thermochemical reactions, whereas the pure vanadia powders undergo melting and show non-cyclic redox behaviour. These materials achieve noteworthy syngas production rates of up to 500 mmol mol min during the long-term stability test of 100 CO splitting cycles. Interestingly, the cerium ions are mobile between the lattice and the surface of the Ce-doped vanadia powders during the repeated reduction and oxidation reactions and contribute towards the cyclic syngas production. However, this also causes the formation of the CeVO phase in Ce-rich powders, which increases the H/CO ratios and lowers fuel selectivity, which can be controlled by optimizing the cerium concentration. These findings are noteworthy towards the experimental approach of evaluating the oxygen carriers with the help of advanced characterization techniques.
合成气生产——太阳能热化学还原-氧化反应是通往可持续碳中性燃料的一条有前景的途径。具有相当热稳定性和化学稳定性的氧载体的氧化还原能力是非常理想的。在本研究中，我们报道了用于甲烷高温热化学循环重整与水分解和一氧化碳分解反应耦合的铈掺杂氧化钒结构。掺入少量大的铈阳离子会引发钒的价态转变并部分形成分离的CeVO相。更重要的是，铈的高效离子迁移率与氧化钒的高氧交换容量的有效结合在热化学反应过程中实现了协同且可循环的氧化还原性能，而纯氧化钒粉末会发生熔化并表现出非循环的氧化还原行为。在100次一氧化碳分解循环的长期稳定性测试中，这些材料实现了高达500 mmol mol⁻¹ min⁻¹的显著合成气产率。有趣的是，在反复的还原和氧化反应过程中，铈离子在铈掺杂氧化钒粉末的晶格和表面之间移动，并有助于循环合成气的产生。然而，这也导致在富铈粉末中形成CeVO相，这会增加氢碳比并降低燃料选择性，这可以通过优化铈浓度来控制。这些发现对于借助先进表征技术评估氧载体的实验方法具有重要意义。
