Understanding the fundamental electrical and photoelectrochemical behavior of a hematite photoanode

• Published in: Physical chemistry chemical physics : PCCP 2016-08, Vol.18 (31), p.2178-21788
• Main Authors: Soares, Mario R. S, Gonçalves, Ricardo H, Nogueira, Içamira C, Bettini, Jefferson, Chiquito, Adenilson J, Leite, Edson R
• Format: Article
• Language: English
• Subjects: Atmospheres; Electrodes; Grain boundaries; Heat treatment; Hematite; Oxygen; Semiconductors; Sintering
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c6cp03680e

Hematite is considered to be the most promising material used as a photoanode for water splitting and here we utilized a sintered hematite photoanode to address the fundamental electrical, electrochemical and photoelectrochemical behavior of this semiconductor oxide. The results presented here allowed us to conclude that the addition of Sn 4+ decreases the grain boundary resistance of the hematite polycrystalline electrode. Heat treatment in a nitrogen (N 2 ) atmosphere also contributes to a decrease of the grain boundary resistance, supporting the evidence that the presence of oxygen is fundamental for the formation of a voltage barrier at the hematite grain boundary. The N 2 atmosphere affected both doped and undoped sintered electrodes. We also observed that the heat treatment atmosphere modifies the surface states of the solid-liquid interface, changing the charge-transfer resistance. A two-step treatment, with the second being performed at a low temperature in an oxygen (O 2 ) atmosphere, resulted in a better solid-liquid interface. Hematite is considered to be the most promising material used as a photoanode for water splitting and here we utilized a sintered hematite photoanode to address the fundamental electrical, electrochemical and photoelectrochemical behavior of this semiconductor oxide.