Plasma-Induced Oxygen Vacancies in Ultrathin Hematite Nanoflakes Promoting Photoelectrochemical Water Oxidation

Abstract

The incorporation of oxygen vacancies in hematite has been investigated as a promising route to improve oxygen evolution reaction activity of hematite photoanodes used in photoelectrochemical water oxidation. However, introducing oxygen vacancies intentionally in α-Fe2O3 for active solar water splitting through facile and effective methods remains a challenge. Herein, air plasma treatment is shown to produce oxygen vacancies in α-Fe2O3, and ultrathin α-Fe2O3 nanoflakes are used to investigate the effect of oxygen vacancies on the performance of photoelectrochemical oxygen oxidation. Increasing the plasma treatment duration and power is found to increase the density of oxygen vacancies and leads to a significant enhancement of the photocurrent response. The nanoflake photoanode with the optimized plasma treatment yields an incident photo-to-current conversion efficiency of 35.4% at 350 nm under 1.6 V vs RHE without resorting to any other cocatalysts, an efficiency far exceeding that of the pristine α-Fe2O3 nanoflakes (∼2.2%). Evidence for the presence of high density of oxygen vacancies confined in nanoflakes is clarified by X-ray photoelectron spectroscopy. The increased number of oxygen vacancies after plasma treatment resulting in an increased carrier density is interpreted as the main cause for the enhanced oxygen evolution reaction activity.

Highly Selective Electrochemical Reduction of Dinitrogen to Ammonia at Ambient Temperature and Pressure over Iron Oxide Catalysts

“…The surface composition of hematite samples before and after annealing (i.e., Fe 2 O 3 -untreated, o-Fe 2 O 3 -Ar,a nd o-Fe 2 O 3 -air) were determined by XPS measurements. [26,27] The concentration values of the three oxygen Figure S2). The Cs ignals originated from the adsorbed carbon species onto the surface of the nanostructured materials and are commonly used as ac harge reference for XPS spectra.…”

Retracted: Dual Effects of Nanostructuring and Oxygen Vacancy on Photoelectrochemical Water Oxidation Activity of Superstructured and Defective Hematite Nanorods

“…From Figure e, the presence of oxygen vacancies is confirmed by analyzing the O 1s peak. The observed peak at 529.9 eV (O 1s) is due to FeOFe bonds, and the shoulder peak at 531.8 eV is attributed to the defect sites with a low oxygen coordination, i.e., oxygen vacancies . This clear shift to the higher binding energy upon Ar treatment likely results from the presence of Fe 2+ , allowing an electron hopping process .…”

“…Introduction of oxygen vacancies into the bulk of semiconductors is an encouraging strategy to improve PEC activity . Recently, researchers reported an alternative route to prepare highly conductive and photoactive α‐Fe 2 O 3 photoanodes by thermal decomposition of FeOOH in an oxygen‐deficient atmosphere (e.g., N 2 /air, Ar) .…”

Oxygen vacancy enhanced photostability and activity of plasmon-Ag composites in the visible to near-infrared region for water purification

“…4d, e), corresponding to the crystal lattice oxygen for O 2− , OH − , while the peak at approximately 532.2 eV is attributed to the defect sites with a low oxygen coordination, i.e. oxygen vacancies [38,39]. The oxygen vacancies were about 2 atom% on the surface of BiO(OH) 0.06 Br 0.94 /Ag/AgBr by deconvolution of the O 1 s spectra and XPS data.…”