A Titanium‐Doped SiO_x Passivation Layer for Greatly Enhanced Performance of a Hematite‐Based Photoelectrochemical System

Abstract

This study introduces an in situ fabrication of nanoporous hematite with a Ti-doped SiOx passivation layer for a high-performance water-splitting system. The nanoporous hematite with a Ti-doped SiOx layer (Ti-(SiOx /np-Fe2 O3 )) has a photocurrent density of 2.44 mA cm(-2) at 1.23 VRHE and 3.70 mA cm(-2) at 1.50 VRHE . When a cobalt phosphate co-catalyst was applied to Ti-(SiOx /np-Fe2 O3 ), the photocurrent density reached 3.19 mA cm(-2) at 1.23 VRHE with stability, which shows great potential of the use of the Ti-doped SiOx layer with a synergistic effect of decreased charge recombination, the increased number of active sites, and the reduced hole-diffusion pathway from the hematite to the electrolyte.

Hematite Photoanode with Complex Nanoarchitecture Providing Tunable Gradient Doping and Low Onset Potential for Photoelectrochemical Water Splitting

“…The differentt hickness is also confirmed by the higher intensity of the (110)p lane XRD reflection for H2 compared with H1 ( Figure S2), which also suggests ap referential growth of H1 and H2 along the (110)c rystallographic direction, the most conductive and desirable for PEC water splitting. [6,9] Strikingly,t he surfacea tomicc oncentration of Sn 4 + in H2 (1.50 %) is 2.4times lower than that of H1 (3.56 %). [6,9] Strikingly,t he surfacea tomicc oncentration of Sn 4 + in H2 (1.50 %) is 2.4times lower than that of H1 (3.56 %).…”

“…[1,2] Semiconductors used in PEC cells split water into oxygen and hydrogen gas by using photoexcited electron-hole pairs (EHP), separated through the formationo ft he space-charge layer (SCL) at the solid/liquid interface. [5,6] Many n-type semiconductors with suitable band-gap energy for absorbing solar light, such as TiO 2 , [7] ZnO, [8] a-Fe 2 O 3 , [9] BiVO 4 , [10] Ta 3 N 5 , [11] and WO 3 , [12] have been extensively investigated as photoanodes for PEC water splitting. [5,6] Many n-type semiconductors with suitable band-gap energy for absorbing solar light, such as TiO 2 , [7] ZnO, [8] a-Fe 2 O 3 , [9] BiVO 4 , [10] Ta 3 N 5 , [11] and WO 3 , [12] have been extensively investigated as photoanodes for PEC water splitting.…”

“…[13][14][15] However, PEC performance of a-Fe 2 O 3 has been hindered by intrinsic material limitations resulting in al ate onsetp otential [0.9-1.1 Vv s. the reversible hydrogen electrode (V RHE )], [16] short hole-diffusion length (L h % 2-4 nm), [17] poor OER performance, [18] and high charge-recombination rate. [3,21] For instance,v arious layers containing TiO 2 , [22] Al 2 O 3 , [23] Ti-doped SiO x , [9] Ga 2 O 3 , [24] and amorphous phosphorus [25] enhanced PEC performance by passivating the surface states of a-Fe 2 O 3 . Various strategies, including the use of passivation layers and/or co-catalysts have shown to reduce the onset potential of a-Fe 2 O 3 .…”

Key Strategies to Advance the Photoelectrochemical Water Splitting Performance of α‐Fe2O3 Photoanode

“…The impurity doping is probably the most common method of modification of photocatalytic semiconductors ,,. The introduction of dopant atoms into the lattice of the semiconductors improves their electronic properties and band structure to ultimately enhance their performance of photocatalysis.…”

“…Coating of Ti‐doped SiO x layer not only reduced the surface charge recombination losses and hole‐diffusion pathway but also enhanced the number of water oxidation active sites on the solid metal oxide surface . A thin overlayer deposition of Ga 2 O 3 by chemical bath deposition method on ultrathin α‐Fe 2 O 3 film demonstrated a 200 mV cathodic shift in V onset .…”