Enhanced photoelectrochemical performance of Cs2RuX6 (X: Cl, Br) in the external magnetic field

Abstract

Photoelectrochemical water splitting to generate green fuel is affected by the kinetic limitations of the oxygen evolution reaction (OER). To enhance the charge transfer processes, an external magnetic field was utilized, and it impacts the performance of the device through improved (i) chemical/electronic effects (spin interactions between reactants and products, charge transport, and carrier lifetime), and (ii) mechanical effects (bubble microhydrodynamics and convective ion migration). Considering the importance of tuning these processes for potential highly efficient systems, we have explored the role of the magnetic field in the OER reaction using panchromatic and stable vacancy-ordered halide perovskites, Cs₂RuX₆ (X-Cl, Br). The magnetic field is shown to improve the performance, but finer analysis reveals the dominant role of chemical/electronic effects over mechanical effects. The bulk charge transport process within the semiconductor and the surface charge transfer process between semiconductor surface and electrolyte is shown to be the major factors for performance enhancement. Forces like the Lorentz and Kelvin forces, induced by the external magnetic field, are found to be much lower than the buoyancy forces, essentially limiting the role of mechanical forces on the PEC performance.