Photocatalytic and Photoelectrochemical Water Oxidation over Metal-Doped Monoclinic BiVO4 Photoanodes

• Published in: ChemSusChem 2012-10, Vol.5 (10), p.1926-1934
• Main Authors: Parmar, Kanak Pal Singh, Kang, Hyun Joon, Bist, Amita, Dua, Piyush, Jang, Jum Suk, Lee, Jae Sung
• Format: Article
• Language: English
• Subjects: doping; electrochemistry; oxidation; photochemistry; water splitting
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201200254

The visible‐light‐induced water oxidation ability of metal‐ion‐doped BiVO4 was investigated and of 12 metal ion dopants tested, only W and Mo dramatically enhanced the water photo‐oxidation activity of bare BiVO4; Mo had the highest improvement by a factor of about six. Thus, BiVO4 and W‐ or Mo‐doped (2 atom %) BiVO4 photoanodes about 1 μm thick were fabricated onto transparent conducting substrate by a metal–organic decomposition/spin‐coating method. Under simulated one sun (air mass 1.5G, 100 mW cm−2) and at 1.23 V versus a reversible hydrogen electrode, the highest photocurrent density (JPH) of about 2.38 mA cm−2 was achieved for Mo doping followed by W doping (JPH≈1.98 mA cm−2), whereas undoped BiVO4 gave a JPH value of about 0.42 mA cm−2. The photoelectrochemical water oxidation activity of W‐ and Mo‐doped BiVO4 photoanodes corresponded to the incident photon to current conversion efficiency of about 35 and 40 % respectively. Electrochemical impedance spectroscopy and Mott–Schottky analysis indicated a positive flat band shift of about 30 mV, a carrier concentration 1.6–2 times higher, and a charge‐transfer resistance reduced by 3–4‐fold for W‐ or Mo‐doped BiVO4 relative to undoped BiVO4. Electronic structure calculations revealed that both W and Mo were shallow donors and Mo doping generated superior conductivity to W doping. The photo‐oxidation activity of water on BiVO4 photoanodes (undoped