Heteroatom doping enables hydrogen spillover via H + /e - diffusion pathways on a non-reducible metal oxide.

Hydrogen spillover, the simultaneous diffusion of protons (H + ) and electrons (e - ) is considered to be applicable to ubiquitous technologies related to hydrogen but limited to over reducible metal oxides. The present work demonstrates that a non-reducible MgO with heteroatom Al dopants (Al-MgO) allows hydrogen spillover in the same way as reducible metal oxides. Furthermore, a H + storage capacity of this material owing to hydrogen spillover is more than three times greater than those of various standard metal oxides based on H + transport channels within its bulk region. Atomic hydrogen diffuses over the non-reducible Al-MgO produces active H + -e - pairs, as also occurs on reducible metal oxides, to enhance the catalytic performance of Ni during CO 2 hydrogenation. The H + and e - diffusion pathways generated by the heteroatom Al doping are disentangled based on systematic characterizations and calculations. This work provides a new strategy for designing functional materials intended to hydrogen spillover for diverse applications in a future hydrogen-based society.