Design of nitrogen-doped layered tantalates for non-sacrificial and selective hydrogen evolution from water under visible light. Issue 37 (12th September 2016)

• Record Type: Journal Article
• Authors: Suzuki, Hajime; Tomita, Osamu; Higashi, Masanobu; Abe, Ryu
• Is Part Of: Journal of materials chemistry. Volume 4:Issue 37(2016)
• Page Start: 14444
• Page End: 14452
• Publication Date: 2016-09-12
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c6ta04416f
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Nitrogen doping into a series of layered tantalates (ALaTa2 O7, where A = Li, Na, K, Rb, or Cs) was attempted in order to produce materials capable of catalyzing non-sacrificial and endergonic water reduction under visible light. Abstract : Nitrogen doping into a series of layered tantalates (ALaTa2 O7, where A = Li, Na, K, Rb, or Cs) was attempted in order to produce materials capable of catalyzing non-sacrificial and endergonic water reduction under visible light. Heating of KLaTa2 O7 and RbLaTa2 O7 in an NH3 stream at 1073 K led to successful nitrogen doping, accompanied by a significant shift in the absorption edge of the material toward the visible-light region, while similar treatment of the other tantalates resulted in the collapse of the layered structure or partial anion substitution at the surface. Although the NH3 heating of a conventional RbLaTa2 O7 precursor prepared with nearly stoichiometric Rb (Rb/La = 1.2) resulted in the formation of impurities such as Ta3 N5 and amorphous tantalum nitrides, the use of a Rb-rich precursor prepared with excess Rb (Rb/La = 2.4) effectively suppressed this impurity formation. The Rb + cations in the prepared pure nitrogen-doped sample were exchanged with H + to facilitate the intercalation of water, and a cationic Pt precursor was then selectively introduced into the interlayers and photocatalytically reduced to Pt metal particles. The internally platinized H + /RbLaTa2 O7− x N y showed stable H2 evolution in the presence of I − as an electron donor under visible light, accompanied by the generation of I3 − . Although the externally platinized H + /RbLaTa2 O7− x N y sample and other bulk-type photocatalysts such as Ta3 N5 generated H2 in the presence of a sacrificial electron donor, H2 evolution was negligible in the presence of I − . The stable H2 evolution over the internally platinized H + /RbLaTa2 O7− x N y sample is due to the suppressed backward reduction of I3 − to I − at selective reduction sites in the interlayer spaces, which are accessible only to cationic species and water.