Facile Fabrication of a Highly Crystalline and Well-Interconnected Hematite Nanoparticle Photoanode for Efficient Visible-Light-Driven Water Oxidation

Abstract

Facile and scalable fabrication of α-Fe 2 O 3 photoanodes using a precursor solution containing Fe III ions and 1-ethylimidazole (EIm) in methanol was demonstrated to afford a rigidly adhered α-Fe 2 O 3 film with a controllable thickness on a fluorine-doped tin oxide (FTO) substrate. EIm ligation to Fe III ions in the precursor solution brought about high crystallinity of three-dimensionally well-interconnected nanoparticles of α-Fe 2 O 3 upon sintering. This is responsible for the 13.6 times higher photocurrent density (at 1.23 V vs reference hydrogen electrode (RHE)) for photoelectrochemical (PEC) water oxidation on the α-Fe 2 O 3 (w-α-Fe 2 O 3 ) photoanode prepared with EIm compared with that (w/o-α-Fe 2 O 3 ) prepared without EIm. The w-α-Fe 2 O 3 photoanode provided the highest charge separation efficiency (η sep ) value of 27% among the state-of-the-art pristine α-Fe 2 O 3 photoanodes, providing incident photon-to-current conversion efficiency (IPCE) of 13% at 420 nm and 1.23 V vs RHE. The superior η sep for the w-α-Fe 2 O 3 photoanode is attributed to the decreased recombination of the photogenerated charge carriers at the grain boundary between nanoparticles, in addition to the higher number of the catalytically active sites and the efficient bulk charge transport in the film, compared with w/o-α-Fe 2 O 3 .

A highly efficient and stable platinum film deposited via a mixed metal-imidazole casting method as a benchmark cathode for electrocatalytic hydrogen evolution

“…6) containing the components ( R ct bulk and CPE bulk ) for the bulk charge transport in the film with the surface trap components ( R ct surf and CPE surf ), where R ct and CPE are charge transfer resistance and constant phase element, respectively, in addition to the solution phase resistance ( R sol ). 37,39 The simulated curves by the equivalent circuit were well-fitted to these Nyquist plots for both electrodes, and the given element parameters of the equivalent circuit are summarized in Table 1. The R sol values are nearly the same in the range of 3.2–3.3 Ω cm −2 for both electrodes.…”

“…13,14,[22][23][24][33][34][35][36] We have recently reported a unique preparation technique called the "MiMIC method" for preparation of single-or multimetal oxide lms adhered rigidly on various electrode substrates. 8,[37][38][39][40] In this method, the metal oxide lms are formed by casting precursor methanol solutions (or suspensions) of the corresponding metal ions and imidazole derivatives, followed by calcination. Imidazole derivatives have been considered to act as a binder for metal oxide nanoparticles, resulting in three-dimensionally well-interconnected nanoparticles on the electrode surface.…”

“…Imidazole derivatives have been considered to act as a binder for metal oxide nanoparticles, resulting in three-dimensionally well-interconnected nanoparticles on the electrode surface. 39 The thicknesses of the formed films are controllable by the concentration of the metal ions or the cast volume of the precursor solutions (or suspensions). This method is useful for mass production of a large variety of metal oxide-based films that are required for practical device fabrications due to advantages of its simplicity and scalability.…”

Perfect Matching Factor between a Customized Double-Junction GaAs Photovoltaic Device and an Electrolyzer for Efficient Solar Water Splitting

“…The FeNiWO x film easily suffered from the detachment from the NF surface in the absence of MeIm in the precursor suspension. MeIm is ligated to any metal ions in the precursor suspension to act as a binder for FeNiWO x nanoparticles, which is important for the rigid adherability of the FeNiWO x film on the NF surface. ,− The coverage (Γ cov ) of the deposited FeNiWO x film linearly increased from 0 to 35 mg cm –2 with the increase in the total concentration of metal ions in the precursor solution from 0 to 250 mM, indicating that the Γ cov value can be easily controlled by the total concentration of the precursor suspensions.…”

One-step chemical vapor deposition fabrication of Ni@NiO@graphite nanoparticles for the oxygen evolution reaction of water splitting

“…Compared with biomass hydrogen production, hydrocarbon pyrolysis and thermochemical water splitting, electrochemical hydrogen evolution has received extensive attention and possesses several advantages such as a simple process, no carbon pollution, and high product purity. 1,2 The oxygen evolution reaction (OER) (2H 2 O ¼ O 2 + 4H + + 4e À ), the half reaction of water splitting, involves the transfer of four electrons and requires a high overpotential (1.23 V), which greatly limits its overall efficiency. 3,4 Therefore, the exploration of highly efficient OER electrocatalysts is a key factor in increasing the efficiency of water splitting.…”