Ir-phosphate cocatalyst for photoelectrochemical water oxidation using α-Fe₂O₃

Abstract

is an ideal photoanode for solar water oxidation owing to its visible light absorbing capability, suitable valence band position, low cost, high abundance, non-toxicity and eco-friendliness. However, the reported efficiencies are very low due to the poor kinetics of water oxidation by photogenerated holes on a-Fe 2 O 3 . In the present study, an a-Fe 2 O 3 electrode is obtained by heating a film of Fe which is prepared by the electrochemical reduction of Fe 2+ ions. Film thickness and calcination temperature are carefully optimized to get a maximum photoresponse in neutral phosphate solution. In order to improve the water oxidation kinetics and reduce the charge carrier recombination, an iridium-phosphate (Ir-Pi) catalyst is electrodeposited on the surface of a-Fe 2 O 3 . Ir-Pi is found to reduce the OER onset potential by 350 mV, and enhances the photocurrent density by 3 times at 1.23 V vs. RHE.

Enhanced Oxygen Evolution Reaction Activity of Nanoporous SnO2/Fe2O3/IrO2 Thin Film Composite Electrodes with Ultralow Noble Metal Loading

“…Based on these results and the band alignment of our semiconductors ( Figure ),[7a,29] we expect a photoelectrochemical activity upon solar irradiation. The experimental data are presented in Figure 9 and Figure S5 in the Supporting Information. The initial system, the nanoporous Fe 2 O 3 electrode, only yields negligible photocurrents (Figure a).…”

“…[17a] In fact, our stable dark currents measured at η = 0.38 V in neutral media outperform those of most Fe 2 O 3 ‐based electrodes (some featuring a transparent conductive oxide scaffold and/or an IrO 2 cocatalyst coating) independent of their pH conditions (Table S3, Supporting Information). [16d,17a,b,29a,31] Additionally, the improved catalytic turnover combined with efficient charge carrier separation allows for a significant shift in the photocurrent response by 300 mV to lower E with respect to pure Fe 2 O 3 electrodes.…”

“…Preparation of Nanostructured Composite Electrodes : Nanostructured composite electrodes were prepared in a multistep procedure as illustrated in Figure S1 in the Supporting Information. First the nanoporous alumina oxide templates were obtained via the standard two‐step anodization of aluminum (represented as (a) in Figure S1 in the Supporting Information) 33. Homemade two‐electrode cells consisting of a polyvinyl chloride beaker with four circular openings at the bottom were used to anodize aluminum plates of 2.2 cm diameter, which were therefore held between an O‐ring and a thick copper plate operating as an electrical contact.…”

Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

“…Except for Co-Pi, other metal phosphates, [117,[119][120][121][122] such as Ni-Pi [117] and Fe-Pi [121] are also observed to be capable of facilitating PEC water oxidation. For instance, Gao and co-workers [119] employed a deposit-PEC method to incorporate Ni-Pi with Ti doped α-Fe 2 O 3 , which showed enhanced PEC water oxidation activity.…”

Quantum Dots‐Based Photoelectrochemical Hydrogen Evolution from Water Splitting

“…[ 1d–f,13b,26 ] However, no single semiconductor can satisfy all the above requirements simultaneously so far. [ 13f ] Numerous investigations until now have focused on composite materials, such as cooperating organic dyes [ 27 ] (examples including fluorescein, [ 28 ] QuPh + ‐NA [ 29 ] ) or metal complex (such as Co, [ 30 ] Ir, [ 31 ] and Rh [ 32 ] ) with bulk semiconductors (such as TiO 2 , [ 33 ] C 3 N 4 [ 11b,34 ] ). However, the PEC systems reported so far consistently exhibit low values of current density or poor stability, mainly due to the inherent characteristics of dyes or limited absorption regions of bulk materials.…”