Study of Copper Ferrite as a Novel Photocathode for Water Reduction: Improving Its Photoactivity by Electrochemical Pretreatment

Abstract

Studies on water-splitting p-type oxide electrodes based on nontoxic earth-abundant elements are scarce. Herein, the behavior of electrodes composed of CuFe2 O4 nanoparticles 30 nm in size is presented. The as-prepared CuFe2 O4 nanoporous electrodes exhibit small anodic photocurrents in 0.1 m NaOH. However, an electrochemical pretreatment consisting in the application of sufficiently positive potentials leads to p-type behavior with a photocurrent onset as high as 1.1 V versus the reversible hydrogen electrode, which is among the most positive values reported for an oxide absorbing visible light (band gap of 2.1 eV). This photocurrent is partly due to H2 evolution, but there are also signs of photoreduction of the material. Although the photocurrents are modest, these results point to the possibility of using CuFe2 O4 as a photocathode material in water-splitting devices. Furthermore, the strategy employed for the enhancement in the CuFe2 O4 photoactivity could be extended to other photocathode materials.

Metal Doping to Enhance the Photoelectrochemical Behavior of LaFeO3 Photocathodes

“…Cyclic voltammograms in the dark shown in Figure S2 reveal a capacitive region at positive potentials that fits well with the accumulation region for a p‐type material . As the potential for the onset of the photocurrent is close to the onset of the capacitive currents in the dark, such an accumulation region can tentatively be related to the filling/emptying of valence band states.…”

“…Cyclic voltammograms in the dark shown in Figure S2 reveal ac apacitive region at positive potentials that fits well with the accumulation region for ap -type material. [19,24] As the potential for the onset of the photocurrenti sc lose to the onset of the capacitive currents in the dark, such an accumulation region can tentatively be related to the filling/emptying of valence band states. In this respect, it is important to highlight that DFT calculations reveal that the upper part of the valence band consists mainly of O2ps tates with an important contribution of the Fe 3d e g states.…”

“…Many metal oxides, which include those with a complex stoichiometry (i.e., ternary and quaternary oxides), behave as semiconductors and present a good stability in aqueous environments, which makes them attractive candidates for water splitting devices. Among ternary oxides, p‐type behavior has been uncovered for some perovskites, spinels, delafossites, and scheelites . Perovskite‐type oxides may be a good alternative because most of them exhibit a p‐type semiconductor nature and high stability under illumination in aqueous solutions.…”

“…Amongt ernary oxides, p-type behavior has been uncovered for some perovskites, spinels, delafossites,a nd scheelites. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Perovskite-type oxidesm ay be ag ood alternative because most of them exhibit ap -type semiconductor nature and high stabilityu nder illumination in aqueous solutions. For instance, LaFeO 3 is ap romising candidate, and severals tudies in which this material is investigated in the context of photoelectrochemistry have been reported recently.…”

Self‐Established Rapid Magnesiation/De‐Magnesiation Pathways in Binary Selenium–Copper Mixtures with Significantly Enhanced Mg‐Ion Storage Reversibility

“…The Cu LM2 Auger peaks have been investigated as shown in Figure 6f-i because they are more sensitive to the changes of chemical state compared to the Cu 2p XPS peaks. [31,32] The Cu LM2 peak at point A has a kinetic energy of 917.65 eV corresponding to Cu(0) according to previous reports. [33] No lower kinetic energy is detected for the Cu(I) in range of 916.5 ± 0.5 eV.…”