MetastablePhase Noble-Metal-Free Core–ShellStructure for Efficient Electrocatalytic Nitrobenzene Transfer Hydrogenation

In order to study the catalytic behavior of a metastable-phase catalyst in electrocatalytic hydrogenation, we report a new metastable-phase noble-metal-free core–shell catalyst with a metastable hexagonal closest packed (hcp) phase Ni as the shell and face-centered-cubic (fcc) phase Cu as the core (Cu@hcp Ni NPs) for electrocatalytic hydrogenation of nitrobenzene (Ph-NO₂) to aniline (Ph-NH₂). Using H₂O as the hydrogen source, it achieves up to 99.63% Ph-NO₂ conversion and ∼100% Ph-NH₂ selectivity, with an improved activity turnover frequency (TOF: 6640 h^–1), much higher than those of hcp Ni NPs (5183.7 h^–1) and commercial Pt/C (3537.6 h^–1). It can also deliver a variety of aminoarenes with outstanding selectivity and excellent functional group compatibility with several groups. Mechanistic studies have shown that the introduction of Cu enhances hcp Ni’s ability to dissociate water <i>in situ</i> to produce H* and improves the hydrogenation rate, resulting in the rapid conversion of Ph-NO₂ to the final product Ph-NH₂.