Poisoning mechanism of Ti0.8Zr0.2Cr0.75Mn1.25Ce0.01 hydrogen storage alloy by trace H2S, CO, and CH4

ABSTRACT TiMn 2 -based alloys hold significant application potential due to their moderate hydrogen storage operating conditions and exceptional volumetric hydrogen storage density. Industrial by-product hydrogen, which is widely available and relatively cheap, often contains components such as H 2 S, CO, and CH 4 , whose poisoning mechanism on TiMn 2 -based alloys in the process of hydrogen absorption and desorption remains to be elucidated. In this work, the poisoning mechanisms of H 2 S, CO, and CH 4 on Ti 0.8 Zr 0.2 Cr 0.75 Mn 1.25 Ce 0.01 hydrogen storage alloy were investigated by isothermal adsorption curve, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). The results show that the toxicity of impurity gases on the alloy is CO > H 2 S > CH 4 , and the regeneration difficulty is H 2 S > CO > CH 4 . The hydrogen absorption of the Ti 0.8 Zr 0.2 Cr 0.75 Mn 1.25 Ce 0.02 alloy was restored to 58% after five groups of H 2 S poisoning-regeneration cycles. The hydrogen storage capacity retention rate decreased to 4.03% after five groups of CO poisoning, but the alloy recovered to 96.62% of the hydrogen absorption capacity after regeneration with pure hydrogen. The retention rate of the alloy was 100% after 100 cycles of CH 4 poisoning. According to the results of XPS analysis, two metal sulfides (TiS and ZrS 2 ) and one metal sulfate Zr(SO 4 ) 2 were formed after the Ti 0.8 Zr 0.2 Cr 0.75 Mn 1.25 Ce 0.02 alloy was poisoned by H 2 S. Therefore, H 2 S poisoning belongs to irreversible adsorption and CO belongs to reversible adsorption. The poisoning mechanism may guide the design of alloys for the absorption/desorption of industrial by-product hydrogen.