Design of nitrogen-doped layered tantalates for non-sacrificial and selective hydrogen evolution from water under visible light
Design of nitrogen-doped layered tantalates for non-sacrificial and selective hydrogen evolution from water under visible light
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DOI：
10.1039/c6ta04416f
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发表时间：
2016-09
影响因子：
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通讯作者：
Hajime Suzuki;O. Tomita;Masanobu Higashi;R. Abe
中科院分区：
文献类型：
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作者：
Hajime Suzuki;O. Tomita;Masanobu Higashi;R. Abe
为了制备出能够在可见光下催化非牺牲和自耗水还原的材料，我们尝试将氮掺杂到一系列层状钽酸盐（ALaTa2O7，其中a = Li, Na， K， Rb或Cs）中。在1073 K的NH3流中加热KLaTa2O7和RbLaTa2O7，可以成功地掺杂氮，同时材料的吸收边缘向可见光区明显移动，而其他钽酸盐的类似处理导致层状结构崩溃或表面部分阴离子取代。虽然用接近化学量的Rb （Rb/La = 1.2）制备的传统RbLaTa2O7前驱体在NH3加热后会导致Ta3N5和非晶态氮化钽等杂质的形成，但使用过量Rb （Rb/La = 2.4）制备的富Rb前驱体可以有效抑制这些杂质的形成。制备的纯氮掺杂样品中的Rb+阳离子与H+交换以促进水的插层，然后选择性地将阳离子Pt前驱体引入中间层并光催化还原为Pt金属颗粒。内部镀的H+/RbLaTa2O7−xNy在I−作为电子供体存在的情况下，在可见光下表现出稳定的H2演化，并伴有I3−的生成。虽然外镀的H+/RbLaTa2O7−xNy样品和其他体型光催化剂（如Ta3N5）在牺牲电子供体存在的情况下生成H2，但在I−存在的情况下，H2的演化可以忽略不计。在内部镀铂的H+/RbLaTa2O7−xNy样品上稳定的H2演化是由于在层间空间的选择性还原位点抑制了I3−到I−的反向还原，这些位点只有阳离子物质和水才能进入。
Nitrogen doping into a series of layered tantalates (ALaTa2O7, 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 KLaTa2O7 and RbLaTa2O7 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 RbLaTa2O7 precursor prepared with nearly stoichiometric Rb (Rb/La = 1.2) resulted in the formation of impurities such as Ta3N5 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+/RbLaTa2O7−xNy 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+/RbLaTa2O7−xNy sample and other bulk-type photocatalysts such as Ta3N5 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+/RbLaTa2O7−xNy 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.