Synthesis of Tungsten Trioxide/Hematite Core‐Shell Nanoarrays for Efficient Photoelectrochemical Water Splitting

Abstract

Hematite, with a band gap of 2.0∼2.2 eV suitable for visible light absorption, has emerged to be a promising photoanode material for photoelectrochemical (PEC) catalysis of the oxygen evolution reaction (OER). Herein, we proposed the design and fabrication of a WO3/α‐Fe2O3 core‐shell heterojunction structure, aiming at alleviating the severe mismatch between the relatively long light penetration depth and the extremely short holes diffusion length in α‐Fe2O3. The WO3 nanoarray underlayer is grown directly on the FTO substrate, serving as an effective electron transfer layer and additional light absorber. The α‐Fe2O3 layer is further prepared via spin‐coating and a subsequent calcination process as a thin and uniform shell. The loading amount was regulated with different spin coating times of the precursor. The optimized WO3/α‐Fe2O3 core‐shell nanoarrays display an excellent performance with lower onset potential of 0.65 V vs. RHE and increased photocurrent response of 1.29 mA cm−2 at 1.23 V vs. RHE, much superior than the pristine α‐Fe2O3 or WO3 photoanode. Characterizations demonstrate that both improved light absorption and formation of heterojunction account for the excellent performance. After coating a NiFe‐LDH co‐catalyst layer, the oxygen evolution reaction is further enhanced, and high stability is achieved, benefiting from the efficient charge carrier generation, promoted charge separation in the semiconductor and the rapid consumption of holes for surface reaction.

Hematite as an Electrocatalytic Marker for the Study of Archaeological Ceramic Clay bodies: A VIMP and SECM Study**

“…( 8) as the A HE one and the Bprocess in the same equation as the hematite-catalyzed ORR, one can assume that the parameters S o , g A , h A are essentially identical for all ceramic samples, whereas the p, g B , h B parameters will be sample-characteristic. Then, equation (10) can be rewritten as equation ( 11): (11) where B J and C J represent site-characteristic parameters easily determined from the linear fit of experimental data such as in Figure 11. The corresponding values of the coefficients B J and C J are listed in Table 1.…”

“…[1] Among other compounds, hematite (α-Fe 2 O 3 ) has claimed attention as a photoanode for producing the oxygen evolution reaction (OER) because of its low cost, stability in contact with alkaline solutions, n-type semiconducting properties and band gap of around 2.0 eV. Processes catalyzed by hematite include oxygen reduction reaction (ORR), [2][3][4][5] photoelectrochemical water splitting, [6][7][8][9][10][11] and hydrogen peroxide oxidation. [12] The electrochemistry of hematite has been widely studied.…”

Block Copolymer Templated WO3 Surface Nanolines as Catalysts for Enhanced Epinephrine Sensing and the Oxygen Evolution Reaction

“…also reported that colloidal WO 3 nanowires for solar water splitting and it is reached 1.96 mA cm −2 at 1.23 V RHE under AM1.5G solar irradiation [47] . WO 3 based materials displayed enhanced photo/catalytic activities due to the increasing charge separation, stability and alleviate photogenerated holes accumulation on the surface [48–52] . Nonetheless, we believe that the overall catalytic activity of WO 3 NLs‐ITO in this study is somewhat limited due to the low content of catalyst on the electrode.…”

“…[47] WO 3 based materials displayed enhanced photo/catalytic activities due to the increasing charge separation, stability and alleviate photogenerated holes accumulation on the surface. [48][49][50][51][52] Nonetheless, we believe that the overall catalytic activity of WO 3 NLs-ITO in this study is somewhat limited due to the low content of catalyst on the electrode. Our future studies will attempt to improve on these results through further fine-tuning of the BCP inclusion process for synthesising thicker and denser (in height and diameter) metal oxide structures.…”

Simultaneous Enhancement of Charge Separation and Hole Transportation in a W:α-Fe2O3/MoS2 Photoanode: A Collaborative Approach of MoS2 as a Heterojunction and W as a Metal Dopant

“…The cathodic shift in the onset potential is more pronounced in the 0.5W:α-Fe 2 O 3 /MoS 2 electrode, which implies a shift of the conduction band in the negative region and facile charge transfer pathways. 50,51 The photocurrent response and stability vs time (i−t) curves of pure α-Fe 2 O 3 , 0.25W:α-Fe 2 O 3 , 0.5W:α-Fe 2 O 3 , 1W:α-Fe 2 O 3 , and 0.5W:α-Fe 2 O 3 /MoS 2 were evaluated by chronoamperometry at a constant applied potential of 1.23 V vs RHE for four on−off cycles under 1-sun illumination, and the results are shown in Figure S7c,d. The photocurrents in these four cycles were measured under periodic illumination (30 s light on and 15 s light off) in 1 M NaOH solution as an electrolyte.…”