Breaking the scaling relation for the Tafel hydrogen evolution step by proximity induced magnetism

We present a Density Functional Theory (DFT) study of the role of spin-polarisation at Au and Pt surfaces for the kinetics of the Tafel Hydrogen Evolution Step (THES). The DFT simulations uncover an electrode-dependent response to spin-polarisation at the surface with the ensuing possibility of both increasing (Pt) or decreasing (Au) the rate-determining barrier for the THES. The DFT simulations identify the leading terms of the calculated THES enhancement (Pt) and suppression (Au) in the different electronic and phonon (zero-point energies and vibrational entropy) responses to spin-polarisation at the electrode surface. Electrochemical characterization of the THES in Ar-saturated 0.5 M KHCO₃ solution on Au and Pt thin-film capped, ferromagnetic multi-layer (Pt/CoxBy/Ir) electrodes confirms increases of up to 30% for Pt (-0.15 V vs. RHE), and over 95% suppression for Au (-0.5 V vs. RHE), depending on the thickness of the catalytic cap [1]. The approach, understood to rest on proximity induced magnetism at the Pt and Au thin-films, opens new scalable avenues to circumvent scaling relations on existing electrocatalyst surfaces, which could be applied to a range of sustainable chemistry and energy applications.

[1] UKIPO Application No. 2415085.6 (14/10/2024)