Introduction . Hydrogen spillover is a highly important process governing the performance of various hydrogen-related chemical and physical applications such as hydrogen embrittlement1 , 2 , 3, atomic metal hydrogen4 , 5, hydrogen storage6 , 7, hydrogen sensing8, and hydrogen-involved catalysis9 , 10 , 11. In fact, the research on hydrogen spillover has been a long journey since its first discovery on WO 3 /Pt system12, during which some ...