Direct magnetic enhancement of electrocatalytic water oxidation in alkaline media

Abstract

Industrially profitable water splitting is one of the great challenges in the development of a viable and sustainable hydrogen economy. Alkaline electrolysers using Earth-abundant catalysts remain the most economically viable route to electrolytic hydrogen, but improved efficiency is desirable. Recently, electron spin polarization was described as a potential way to improve water-splitting catalysis. Here, we report the significant enhancement of alkaline water electrolysis when a moderate magnetic field (≤450 mT) is applied to the anode. Current density increments above 100% (over 100 mA cm −2) were found for highly magnetic electrocatalysts, such as the mixed oxide NiZnFe 4 O x. Magnetic enhancement works even for decorated Ni-foam electrodes with very high current densities, improving their intrinsic activity by about 40% to reach over 1 A cm −2 at low overpotentials. Thanks to its simplicity, our discovery opens opportunities for implementing magnetic enhancement in water splitting.

Antiferromagnetic Inverse Spinel Oxide LiCoVO4 with Spin‐Polarized Channels for Water Oxidation

“…The magenetisms from spin‐up Co 2+ layer and Co 2+ spin‐down layer are canncelled by each other, resulting in zero net magnetism. The enhancement of OER catalytic actvity by magnetic field was recently reported by Galán‐Mascarós et al The finding showed that the magnetic enhancement of catalysts' OER activity has certain coorelation to the catalysts' bulk magnetization. Under moderate magnetic field, materials with higher bulk magnetization exhibit larger enhancement of their OER activities .…”

“…The enhancement of OER catalytic actvity by magnetic field was recently reported by Galán‐Mascarós et al The finding showed that the magnetic enhancement of catalysts' OER activity has certain coorelation to the catalysts' bulk magnetization. Under moderate magnetic field, materials with higher bulk magnetization exhibit larger enhancement of their OER activities . Therefore, we investigated the effect of an external magnetic field on LiCoVO 4 and ZnCo 2 O 4 by applying a 250 mT magnetic field during chronoamperometry measurement.…”

“…Because both LiCoVO 4 and ZnCo 2 O 4 are antiferromagnetic materials with very low magnetic susceptibility, an external magnetic field is not expected to enhance their OER activity, which is consistent with the previous report. [24] The extenal magnetic field has no effect on LiCoVO 4 OER performance and also indicates that the Co 2+ ions with positive and negative magnetic moments alternating with layer arrangment are stable in bulk oxide at room temperature.…”

“…Under moderate magnetic field, materials with higher bulk magnetization exhibit larger enhancement of their OER activities. [24] Therefore, we investigated the effect of an external magnetic field on LiCoVO 4 and ZnCo 2 O 4 by applying a 250 mT magnetic field during chronoamperometry measurement. The results ( Figures S7 and S8, Supporting Information) indicate that the external magnetic field does not enhance their OER activity.…”

Catalytic resonance theory: parallel reaction pathway control

“…11,12 An alternative strategy for catalytic reaction control proposes a dynamic catalytic surface, whereby the binding energy (i.e., heat of adsorption) of surface intermediates and associated transition state energies oscillate on the time scale of the catalytic turnover frequency. 13 The heat of adsorption of hydrocarbons on metals and metal oxides can be altered by several methods 14,15 including electric and magnetic elds, [16][17][18][19] photocatalysis, 20 surface strain, 21,22 solid electrolytes, [23][24][25][26][27] catalytic diodes, [28][29][30] and back-gated eld effect modulation. [31][32][33] For each combination of catalyst material, chemical mechanism, and method of external stimulus, the dynamic variables including imposed surface binding energy frequency f and amplitude DU comprise a narrow set of conditions which can potentially achieve catalytic turnover frequencies which are orders of magnitude above the static Sabatier maximum (i.e., Balandin-Sabatier volcano peak).…”