Dual-functional CoAl layered double hydroxide decorated α-Fe2O3 as an efficient and stable photoanode for photoelectrochemical water oxidation in neutral electrolyte. Issue 18 (21st April 2017)

• Record Type: Journal Article
• Authors: Chong, Ruifeng; Wang, Baoyun; Su, Caihong; Li, Deliang; Mao, Liqun; Chang, Zhixian; Zhang, Ling
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 18(2017)
• Page Start: 8583
• Page End: 8590
• Publication Date: 2017-04-21
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7ta01586k
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : An α-Fe2 O3 photoanode was decorated with a dual-functional CoAl layered double hydroxide for photoelectrochemical water oxidation. The composite photoanode exhibits high efficiency and excellent stability in neutral electrolyte. Abstract : As a promising photoanode material, hematite (α-Fe2 O3 ) can be used for photoelectrochemical (PEC) water oxidation but there are still great challenges, such as low efficiency and poor stability in neutral pH electrolyte, before it can be used in practice. Herein, a CoAl layered double hydroxide (CoAl-LDH) has been deposited in situ onto α-Fe2 O3 nanoarrays. The PEC performances of the resulting composite photoanodes (CoAl-LDH/α-Fe2 O3 ) towards water oxidation were investigated in neutral pH electrolyte. Contrastive experiments indicated that Co 2+ in CoAl-LDH provided active catalytic sites for water oxidation, while Al 3+ was inactive and offered support for the layered skeleton. CoAl-LDH could have a dual role as an efficient cocatalyst to lower the onset potential and enhance the photocurrent of α-Fe2 O3, and as an effective protector of α-Fe2 O3 from corrosion in neutral pH electrolyte. Relative to that of bare α-Fe2 O3, a ∼250 mV negatively shifted onset potential and an almost 9-fold enhancement in photocurrent density at 1.23 V vs. RHE were observed with CoAl-LDH/α-Fe2 O3 . Moreover, CoAl-LDH/α-Fe2 O3 showed excellent stability at 1.23 V vs. RHE with a steady photocurrent of ∼2 mA cm −2 even after 2 h of irradiation, which was very close to 100% of the initial value. Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance at the interface of α-Fe2 O3 /electrolyte was significantly decreased by CoAl-LDH decoration. Using H2 O2 as a hole scavenger, the charge injection efficiency at the interface of CoAl-LDH/α-Fe2 O3 and electrolyte was recorded as 84% at 1.23 V vs. RHE, which was 4-fold higher than that at the interface of α-Fe2 O3 and electrolyte. This work demonstrates that CoAl-LDH decorated semiconductors have great potential as efficient and stable photoanodes towards high PEC performance in neutral pH electrolyte.