Dual modification of hematite photoanode by Sn-doping and Nb₂O₅ layer for water oxidation

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Porous hematite (α-Fe<SUB>2</SUB>O<SUB>3</SUB>) films doped with Sn(IV) and coated with an ultrathin (∼2nm thick) Nb<SUB>2</SUB>O<SUB>5</SUB> passivation layer were synthesized, and the photoelectrochemical (PEC) water oxidation performance and durability of the hematite were examined in detail. As compared to hematite samples modified by either doping or passivation, dual-modified hematite exhibited a promising PEC water oxidation performance under AM 1.5 irradiation. A stable photocurrent was maintained under prolonged irradiation over 24h, while O<SUB>2</SUB> was produced from water with a Faradaic efficiency of over 80% without showing any sign of deactivation. This performance and durability could be decoupled into separate effects of Sn doping and Nb<SUB>2</SUB>O<SUB>5</SUB> layer via in-depth surface characterization and electrochemical analyses. Sn doping increased the donor density (<I>N</I> <SUB>d</SUB>) of bare hematite by a factor of 20 and significantly improved its conductivity, leading to enhanced charge transfer efficiency. The Nb<SUB>2</SUB>O<SUB>5</SUB> layer exerted an effect similar to Sn doping because of the diffusion of a fraction of Nb(V) into the hematite lattice during the annealing process at 700°C. The primary effect of the Nb<SUB>2</SUB>O<SUB>5</SUB> layer is to passivate the hematite surface and make the surface more reactive toward the oxygen evolution through water oxidation. These effects are synergistically combined in the dual-modified hematite electrode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hematite doped with Sn(IV) and coated with an ultrathin Nb<SUB>2</SUB>O<SUB>5</SUB> layer are synthesized. </LI> <LI> Dual-modified hematite exhibits remarkably high photoelectrochemical efficiencies. </LI> <LI> A stable photocurrent is maintained under prolonged irradiation over 24h. </LI> <LI> O<SUB>2</SUB> is linearly produced from water with an efficiency of >80% without deactivation. </LI> <LI> The effect is in-depth studied in terms of charge separation and injection. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>