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 CO₂ 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.