Spin Polarization: A New Frontier in Efficient Photocatalysis for Environmental Purification and Energy Conversion

Abstract

As a promising strategy to improve photocatalytic efficiency, spin polarization has attracted enormous attention in recent years, which could be involved in various steps of photoreaction. The Pauli repulsion principle and the spin selection rule dictate that the behavior of two electrons in a spatial eigenstate is based on their spin states, and this fact opens up a new avenue for manipulating photocatalytic efficiency. In this review, recent advances in modulating the photocatalytic activity with spin polarization are systematically summarized. Fundamental insights into the influence of spin‐polarization effects on photon absorption, carrier separation, and migration, and the behaviors of reaction‐related substances from the photon uptake to reactant desorption are highlighted and discussed in detail, and various photocatalytic applications for environmental purification and energy conversion are presented. This review is expected to deliver a timely overview of the recent developments in spin‐polarization‐modulated photocatalysis for environmental purification and energy conversion in terms of their practical applications.

Spin-Polarized Charge Separation at Two-Dimensional Semiconductor/Molecule Interfaces

“…When longrange magnetic order is present, electron transport and transfer also become spin-dependent. 7,8 The synergetic operation of the above mechanisms underlies the enhanced efficiency and selectivity of (photo)electrocatalytic oxygen evolution 9,10 and other chemical transformations 11 by spin-polarized catalysts. In these demonstrations, spin polarization results from the catalyst being ferromagnetic, magnetically doped, or subjected to an external magnetic field.…”

“…The adsorption energies of reactants, promoters, and transition states are related to the spin configuration of the active sites on a solid surface. − This implies a preferential spin orientation for each adsorbed species on a spin-polarized catalytic site, which could favor triplet products from radical pair recombination or singlets through exchange interaction. − In photoelectrochemical cells, charge separation times can be increased if the spin polarization lifetimes are different for photoexcited electrons and holes since recombination requires spin angular momentum conservation. When long-range magnetic order is present, electron transport and transfer also become spin-dependent. , The synergetic operation of the above mechanisms underlies the enhanced efficiency and selectivity of (photo)­electrocatalytic oxygen evolution , and other chemical transformations by spin-polarized catalysts. In these demonstrations, spin polarization results from the catalyst being ferromagnetic, magnetically doped, or subjected to an external magnetic field.…”