A precious metal-free solar water splitting cell with a bifunctional cobalt phosphide electrocatalyst and doubly promoted bismuth vanadate photoanode

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2018, Vol.6 (3), p.1266-1274
• Main Authors: Kim, Jin Hyun, Han, Suenghoon, Jo, Yim Hyun, Bak, Yunji, Lee, Jae Sung
• Format: Article
• Language: English
• Subjects: Bismuth oxides; Cathodes; Chemical evolution; Cobalt; Cobalt oxides; Electrocatalysts; Energy conversion efficiency; Heavy metals; Hydrogen; Hydrogen evolution reactions; Metal foams; Metals; Noble metals; Phosphides; Photoanodes; Photovoltaic cells; Platinum; Solar power; Splitting; Vanadate; Vanadates; Water splitting
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta09134f

A bifunctional cobalt phosphide (CoP) electrocatalyst is applied to a doubly promoted BiVO 4 photoanode as an oxygen evolution as well as to a cathode as a hydrogen evolution reaction (HER) catalyst to establish a photoelectrochemical (PEC) water splitting cell made of only earth abundant elements without any precious metals. Although the intrinsic HER activity of CoP is lower than Pt/C, CoP can replace Pt as the cathode of PEC water splitting cells without any significant loss in performance. During the water splitting reaction, the cathode remains as CoP, but CoP loaded on the BiVO 4 photoanode turns into amorphous CoO x -HPO y with its chemical state and performance very similar to those of well-known cobalt phosphate electrocatalysts. A tandem cell composed of CoP/hydrogen-treated, 1% Mo-doped BiVO 4 as the photoanode, a CoP/Ni foam as the cathode and a 2-piece, series connected crystalline Si solar cell as the bias power generator demonstrates stable unassisted water splitting with a solar-to-hydrogen conversion efficiency of 5.3% under simulated solar light, which represents the highest among reported precious metal-free unassisted solar water splitting devices. A bifunctional cobalt phosphide (CoP) electrocatalyst is applied to a doubly promoted BiVO 4 photoanode as an oxygen evolution as well as to a cathode as a hydrogen evolution reaction (HER) catalyst to establish a photoelectrochemical (PEC) water splitting cell made of only earth abundant elements without any precious metals.