Photothermal–Magnetic Synergistic Effects in an Electrocatalyst for Efficient Water Splitting under Optical–Magnetic Fields

Abstract

The slow oxygen evolution reaction (OER) limits water splitting, and external fields can help improve it. However, the effect of a single external field on OER is limited and unsatisfactory. Furthermore, the mechanism by which external fields improve OER is unclear, particularly in the presence of multiple fields. Herein, we propose a strategy for enhancing the OER activity of a catalyst using the combined effect of an optical‐magnetic field and study the mechanism of catalytic activity enhancement. Under the optical‐magnetic field, Co3O4 reduces the resistance by increasing the catalyst temperature. Meanwhile, CoFe2O4 further reduces the resistance via the negative magnetoresistance effect, thus decreasing the resistance from 16 Ω to 7.0 Ω. Additionally, CoFe2O4 acts as a spin polarizer, and electron polarization results in a parallel arrangement of oxygen atoms, which increases the kinetics of the OER under the magnetic field. Benefiting from the optical and magnetic response design, Co3O4/CoFe2O4@Ni foam requires an overpotential of 172.4 mV to reach a current density of 10 mA·cm−2 under an optical‐magnetic field, which is significantly higher than those of recently reported state‐of‐the‐art transition‐metal‐based catalysts.This article is protected by copyright. All rights reserved

Enhanced Photocatalytic CO2 Reduction Performance via Photothermal–Magnetic Synergistic Effects for Solar Fuel Production

“…Moreover, a negative MR effect was observed in ZnFe 2 O 4 , which decreased with increasing temperature . The higher saturation magnetization indicates a higher relative permeability of the sample, resulting in a lower MR value that promotes charge carrier’s transport . As a result, the increase in light intensity led to an elevated temperature, which weakened the promoting effect of the magnetic field on carrier transport through the interface and therefore diminished the enhancement effect on catalytic performance.…”

“…38 The higher saturation magnetization indicates a higher relative permeability of the sample, resulting in a lower MR value that promotes charge carrier's transport. 39 As a result, the increase in light intensity led to an elevated temperature, which weakened the promoting effect of the magnetic field on carrier transport through the interface and therefore diminished the enhancement effect on catalytic performance. In addition, the photocatalytic performance in our study was compared with previous reports, as illustrated in Table S2.…”

Optimizing Water Oxidation Kinetics by Modulating Spin Alignment through Non-metal Vacancy Engineering

“…The investigation of magnetic properties indicated that the NiFeP has paramagnetic behavior with various magnetizations depending on the external magnetic field at room temperature. Besides, the saturation magnetization value of NiFeP-AH is much higher than that of NiFeP-BH, indicating that the NiFeP-AH might have lower magnetoresistance ( R M ), which can be deduced as follows R M = L / μ A μ = 2 M S 3 H K + 1 where L is the magnetic circuit length, μ is the relative permeability, A is the magnetic circuit cross-sectional area, and M s and H k are the magnetic saturation magnetization and the anisotropic equivalent field, respectively. It is suggested that NiFeP-AH would endow the electrode with a high magnetic property after magnetization.…”

“…The investigation of magnetic properties indicated that the NiFeP has paramagnetic behavior with various magnetizations depending on the external magnetic field at room temperature. Besides, the saturation magnetization value of NiFeP-AH is much higher than that of NiFeP-BH, indicating that the NiFeP-AH might have lower magnetoresistance (R M ), which can be deduced as follows 22 = R L A / M…”

“…Refining the earlier discussion, the augmentation of OER activity through the application of a magnetic field is rooted in the principles of spin-restricted reactions, fostering parallel alignment among oxygen radicals, and the negative magnetoresistance effect, which is inversely proportional to saturation magnetization. , In this case, NiFe bimetallic phosphides have garnered significant attention owing to their magnetic properties and high electrical conductivity. , Additionally, the presence of phosphorus (P) stabilizes the Ni and Fe elements, leading to the formation of an amorphous metal with macroscopic conductivity. − The unsaturation of P with Ni and Fe can lead to a high density of active sites on the surface. Moreover, the negatively charged nature of phosphorus serves as a proton acceptor, facilitating hydrogen desorption .…”