The enhanced hydrogen storage performance of Zr0.8HfxTi0.2-xCo (x=0, 0.05, 0.1, 0.15) alloys via Hf doping

Single element doping is considered feasible strategy to boost the hydrogen storage performance of ZrCo based alloy. However, single element doping has limitations. Element composition design and multielement co-doping are considered research trends. In this study, the quaternary alloys of Zr 0.8 Hf x Ti 0.2-x Co (x = 0.05, 0.1, 0.15) were designed via Hf doping based Zr–Ti–Co alloy, and the hydriding/dehydriding kinetics and cycling stability were significantly enhanced. The base alloy Zr 0.8 Ti 0.2 Co exhibits a CsCl-type cubic phase, while the addition of Hf introduces a secondary HfCo phase. The hydriding/dehydriding kinetics is enhanced sharply due to the catalytic effect of HfCo second phase. The cyclic retention rate of Zr 0.8 Hf 0.1 Ti 0.1 Co alloy increases to 76.9 % (compared to Zr 0.8 Ti 0.2 Co with retention rate 65.9 %), which is attributed to the good anti-disproportionation performance and better structural stability during absorption/desorption process. The design of quaternary alloys is an effective approach to enhance the hydrogen storage properties of ZrCo based alloy and provides elemental alloying design strategies for ZrCo based alloy. • The quaternary Zr-Hf-Ti-Co alloys were designed. • The hydriding/dehydriding kinetics is significantly enhanced by Hf doping. • The secondary HfCo phase acts as the catalytic effect on the kinetic property. • The cycling stability of Zr–Ti–Co based alloys is improved by Hf doping.