Achieving excellent CO2 poisoning resistance of ZrCo hydrogen isotope storage material by surface reconstruction strategy

Abstract

ZrCo alloy has been treated as the most promising candidate for hydrogen isotope storage in the International Thermonuclear Experimental Reactor (ITER). However, its poisoning resistance properties still remain challenging since the presence of impurity gas of CO2. Herein, the poisoning resistance behaviors and mechanism of ZrCo in H2+CO2 mixed gas were systematically investigated. Surprisingly, even trace amounts of CO2 can strongly deteriorate hydrogenation kinetics of ZrCo, which can be mitigated by further increasing the inputting pressure of the mixed gas. Such poisoning phenomenon can be attributed to the selective preferential absorption of CO2 on the ZrCo surface. Namely, the absorbed CO2 occupies the active sites on the surface and thus significantly blocks the absorption or dissociation of H2. Therefore, we proposed an in-situ surface reconstruction strategy by high-temperature treatment at 550 °C in H2+CO2 mixed gas. Specifically, in-situ formed metallic Co nanoclusters were generated on ZrCo surface, which are not only tough to be poisoned by CO2 contamination, but also can function as the catalytic active sites for H2 dissociation. Thus, an enhanced CO2 poisoning tolerance of ZrCo was achieved through the novel in-situ surface reconstruction strategy.