Sn-doped hematite films as photoanodes for efficient photoelectrochemical water oxidation

Abstract

Sn-doped hematite films were electrochemically deposited on a fluorine-doped tin oxide substrate for use as an anode for efficient photoelectrochemical water oxidation.

Fe2PO5‐Encapsulated Reverse Energetic ZnO/Fe2O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

“…It is clear that the onset potentialso fd ark currentd ecreasen otably following PH 3 annealing, whichi ndicates accelerated water oxidation kinetics on the surface of the samples. [44] Considering the onset potentials hift of the ZnO/Fe 2 O 3 photoanode after PH 3 annealing, it is possible that the overlayer acts as aw ater oxidation co-catalyst as the well-known CoPi does in hematite, [45] thus altering the onset potential for both photocurrenta nd dark current.…”

“…RHE) and Nyquist plots are shown in Figure 8d.T he experimental data were fitted by using an equivalent circuit R s (CPE-R p ), in which R s is the ohmic contribution,C PE is ac onstantp hase element that takes into account non-idealities in the capacitance of the Helmholtz layer,a nd R p is the charge-transfer resistance. [44] In this mode, the response at the low-frequency region accounts for the charge-transfer process in the interface between the semiconductor and electrolyte. Moreover, the response at high frequency is designatedt oa ne lectronic process, which is normally faster than the processo ccurring in the solution-involved interface, in the bulk of electrode.…”

“…The total capacitance C can be expressed as: 1=C ¼ 1=C 1 þ 1=C 2 . [57] Although the reported carrier density of ZnO (10 18 cm À3 ) [14] is relatively lower than that for Fe 2 O 3 (10 19 cm À3 ), [44,58] the electron density of electrolyte is far lower than both ZnO and Fe 2 O 3 .T his indicates that the capacitance of the ZnO/Fe 2 O 3 core-shell electrode could be dominantly affected by the capacitance generated from the Fe 2 O 3 -electrolyte interface and thus the total capacitance is approximately equal to the depletion layer capacitance of Fe 2 O 3 .F or EIS testing, af ixed bias potential of 1.5 Vv s. RHE was used and the light intensity was set to 50 mW cm À2 .T he capacitance was extracted from the EIS spectra by use of an equivalent circuit R s (CPE-R p ), where R s is the ohmic contribution, CPE is ac onstant phase element that takes into account non-idealities in the capacitance of the Helmholtz layer,a nd R p is the charge-transfer resistance. IPCE spectra were measured using light from a3 00 Wx enon lamp that was focused by ap arabolicre flector and passed through am onochromator,a t1 .23 V bias versus RHE.…”

Controlled Aqueous Growth of Hematite Nanoplate Arrays Directly on Transparent Conductive Substrates and Their Photoelectrochemical Properties

“…This could be due to different synthesis processes and a relatively larger surface area of branched nanosheets in the report. With no significant change in morphology, crystalline structure, and light absorption (see the Supporting Information), the Sn‐doped hematite nanoplate film displays an enhanced photocurrent of 0.26 mA cm −2 at 1.23 V (vs. RHE), which demonstrates that Sn impurity improves the electron conductivity of hematite . When Sn‐doped hematite is modified with Co‐Pi co‐catalyst (abbreviated as Sn‐Fe 2 O 3 /CoPi), the generated photocurrent further increases to 0.60 mA cm −2 at 1.23 V (vs. RHE).…”

“…This means that intentional Sn doping is more effective for improving the electrical conducting property of hematite nanoplates by increasing its donor density than Sn doping caused by Sn diffusion from the FTO substrate. Apparently, as confirmed by other reports, there is a positive relationship between the photocurrent of those samples and their electron‐donor density . The flatband potentials were calculated to be 0.76, 0.97, and 1.17 V (vs. RHE) for bare Fe 2 O 3 , Sn‐Fe 2 O 3 , and Sn‐Fe 2 O 3 /CoPi photoelectrodes, respectively, which indicate that Sn doping and the Co‐Pi co‐catalyst induce a positive shift in flatband potentials.…”