Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

Abstract

The present work compares the oxygen evolution reaction (OER) in electrocatalysis and photocatalysis in aqueous solutions using nanostructured NiFeO x as catalysts. The impacts of pH and reaction temperature on the electrocatalytic and photocatalytic OER kinetics were investigated. For electrocatalysis, a NiFeO x catalyst was hydrothermally decorated on Ni foam. In 1 M KOH solution, the NiFeO x electrocatalyst achieved 10 mA cm −2 at an overpotential of 260 mV. The same catalyst was decorated on the surface of Ta 3 N 5 photocatalyst powder. The reaction was conducted in the presence of 0.1 M Na 2 S 2 O 8 as a strong electron scavenger, thus likely leading to the OER being kinetically relevant. When compared with the bare Ta 3 N 5 , NiFeO x /Ta 3 N 5 demonstrated a 5-fold improvement in photocatalytic activity in the OER under visible light irradiation, achieving a quantum efficiency of 24% at 480 nm. Under the conditions investigated, a strong correlation between the electrocatalytic and photocatalytic performances was identified: an improvement in electrocatalysis corresponded with an improvement in photocatalysis without altering the identity of the materials. The rate change at different pH was likely associated with electrocatalytic kinetics that accordingly influenced the photocatalytic rates. The sensitivity of the reaction rates with respect to the reaction temperature resulted in an apparent activation energy of 25 kJ mol −1 in electrocatalysis, whereas the apparent activation energy in photocatalysis was 16 kJ mol −1 . The origin of the difference in these activation energy values is likely attributed to the possible effects of temperature on the individual thermodynamic and kinetic parameters of the reaction process. The work described herein demonstrates a method of "transferring the knowledge of electrocatalysis to photocatalysis" as a strong tool to rationally and quantitatively understand the complex reaction schemes involved in photocatalytic reactions.

Enhanced Kinetics of Hole Transfer and Electrocatalysis during Photocatalytic Oxygen Evolution by Cocatalyst Tuning

“…7,[22][23][24] In a typical experiment, a total of 0.5 g Ta2O5 was wrapped with quartz wool and placed into a tube furnace. The tube furnace was initially purged with N2 before the introduction of NH3 flow at room temperature.…”

“…6,23,24 The reactant solution was maintained at room temperature by using a flow of cooling water during the reaction. Before irradiation, the reaction vessel was degassed several times to remove air, followed by the introduction of 100 torr of Ar gas into the photocatalytic system.…”

“…One strategy to improve the photocatalytic activity of Ta3N5 is to decorate the surface with an oxygen evolution reaction (OER) electrocatalyst, being an essential component to achieve high efficiency. [21][22][23][24] Previous work has demonstrated that the photocatalytic OER efficiency can be improved by one order of magnitude by the addition of CoOx cocatalyst on the Ta3N5 surface; when appropriate, heat treatment is applied to construct an intimate CoOx-Ta3N5 interface. 22 Generally, the role of the catalyst, which is commonly called a cocatalyst, on the semiconductor surface has been discussed as two-fold: 1) it improves the electrochemical performance by lowering overpotentials for the redox reactions (and resultant electron/hole consumption) and 2) effectively separates the excited charges by using a photocatalyst (semiconductor)-catalyst interface, exploiting the differences in Fermi levels between them.…”

Preparation and Characterization of Nicke-iron Alloy Film as Freestanding Electrode for Oxygen Evolution Reaction

“…First-row transition metal based materials have attracted enormous attentions for OER catalysts due to their low cost and high catalytic activity based on earth-abundant metals [8,9]. Among first-row transition metal materials, nickle and iron based materials possesses outstanding properties including relatively high electrical conductivity and highly catalytic performances for oxygen evolution reacion, making it potential candidates for OER catalysts [10][11][12][13]. However, NiFe based electrocatalysts mentioned in recent literatures, own low stability and poor conductivity [14][15][16][17][18][19].…”

Ab initio assessment of Bi1−xRExCuOS (RE = La, Gd, Y, Lu) solid solutions as a semiconductor for photochemical water splitting

“…The development of efficient semiconductors for sunlight absorption and charge carrier diffusion on one side and efficient electrocatalysts having low overpotential for the two half-reactions on the other side are the two main fields of research for developing heterogeneous photocatalysts for water splitting. [3][4][5][6][7] In this manuscript, we mainly focus on the development of new semiconductors. The first semiconductor investigated for water splitting was TiO 2 in 1972.…”