Kinetics study on the nonlinear modified varying-size model of LaNi₅ during hydrogenation/dehydrogenation

Due to the large kinetics model deviation caused by the actual expansion/shrinkage of LaNi₅ particle during H₂ absorption/desorption process, the nonlinear modified varying-size model (M-VSM) was proposed based on varying-size model (VSM) to calibrate the kinetics equations precisely. The related hydriding and dehydriding kinetics experiments were conducted under various temperatures and pressures, and the model equations of LaNi₅ were achieved based on M-VSM. Both experimental and simulation results confirmed the rate controlling step was internal diffusion. Moreover, the model accuracy of M-VSM was investigated and compared with other conventional models, and the results indicated that M-VSM owned the highest model precision than any other models including shrinking-core model, Johnson-Mehl-Avrami model and Jander diffusion model. Furthermore, the simplified hydriding/dehydriding equations were also derived, whose correlation coefficient R² could reach 0.98 and 0.99, respectively. Hence the M-VSM has favorable accuracy and convenience which will show its great potential application in the future.