Ligand-centered electrocatalytic hydrogen evolution by gallium(iii) triaryl corroles bearing nitro groups

Abstract

Three new gallium(III) triaryl corrole complexes, bearing a nitro group at the ortho-, meta-, or para-position of 5,15-bis(pentafluorophenyl)-10-phenyl corrole (1, 2, and 3), were synthesized and used as electrocatalysts for the hydrogen evolution reaction (HER). All three complexes exhibited good HER activity in both neutral aqueous and organic media. When using p-toluenesulfonic acid (TsOH) as the proton source, complex 1 exhibited the highest maximum turnover frequency (TOF_max) of 387.62 s⁻¹. The catalytic performance follows an order of 1 > 3 > 2, indicating the electron-withdrawing effect of the nitro group may enhance the HER activity. In addition, experiments and density functional theory (DFT) calculations together indicate that the redox process of the complexes is ligand-centered. In particular, the Gibbs free energy profile constructed under the most favourable protonation condition supports a ligand-centered E–C–E–C pathway, providing further evidence for the rationality of the proposed catalytic mechanism.