Spin-Polarized Nonferromagnetic Surfaces for Electrocatalysis: Chemo-Spintronics

TL;DR

This paper shows how nonmagnetic metals like gold and platinum can be made more effective for hydrogen production by using magnetic layers beneath them, opening new possibilities in electrocatalysis.

Contribution

The study introduces a method to achieve spin-polarized catalysis using nonmagnetic metals with magnetic layers, enabling tunable electrocatalytic activity.

Findings

A multilayer structure with a ferromagnetic alloy beneath nonmagnetic metals enhances hydrogen evolution reaction activity.

Proximity-induced magnetism in nonmagnetic metals breaks scaling relationships in catalysis.

Density Functional Theory simulations support the mechanism of spin-polarized catalysis.

Abstract

Catalysts achieve changes in the rate through modification
of the
free energy of adsorbed intermediates and transition states (TrS).
Binding energies of intermediates and TrS are strongly correlated,
and modifications in catalyst composition are often ineffective in
breaking these correlations, leading to minimal change in rate. Such
scaling relationships are reported throughout catalysis. The surface
spin state of a magnetic metal can change adsorption energies, offering
a way to overcome scaling relationships. However, experimentally,
this approach appears reliant on the use of ferromagnetic materials,
limiting applicability. Here, we show that tunable changes in electrocatalytic
activity for the hydrogen evolution reaction (HER) can be achieved
at (originally) nonmagnetic metals (Au and Pt) through the use of
a multilayer electrode structure that contains a ferromagnetic alloy
(CoB) beneath a thin (5–20 nm) film of Pt or Au. Analysis of
the dependence of the catalytic current on the thickness of the Au
or Pt capping layer and on the direction of the stray magnetic field
allows us to rule out the presence of magnetohydrodynamic effects.
Instead, we conclude that transfer of ferromagnetism from the ferromagnet
to the Au or Pt takes place through proximity-induced magnetism (PIM)
via exchange interactions and/or a spin polarized current. Density
Functional Theory simulations trace changes in the breaking of the
scaling relationship for the Tafel HER mechanism. Overall, our experiments
show that thin-film electrodes, based on routine structures from the
spintronics community, are a potentially versatile platform for achieving
spin-polarized catalysis at originally nonmagnetic metals.

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