Photocatalytic Activity of n-Alkylamine and n-Alkoxy Derivatives of Layered Perovskite-like Titanates H2Ln2Ti3O10 (Ln = La, Nd) in the Reaction of Hydrogen Production from an Aqueous Solution of Methanol

Abstract

Two series of hybrid inorganic-organic derivatives, obtained via the modification of protonated Ruddlesden–Popper phases H2Ln2Ti3O10 (Ln = La, Nd) with intercalated n-alkylamines and grafted n-alkoxy groups, have been systematically investigated in relation to photocatalytic hydrogen production from a model of 1 mol % aqueous solution of methanol for the first time. Photocatalytic measurements were performed both for bare samples and for their composites with Pt nanoparticles as a cocatalyst using an advanced scheme, including dark stages, monitoring of the volume concentration of the sample in the reaction suspension during the experiment, shifts of its pH and possible exfoliation of layered compounds into nanolayers. It was found that the incorporation of organic components into the interlayer space of the titanates increases their photocatalytic activity up to 117 times compared with that of the initial compounds. Additional platinization of the hybrid samples’ surface allowed for achieving apparent quantum efficiency of hydrogen evolution of more than 40%. It was established that the photocatalytic activity of the hybrid samples correlates with the hydration degree of their interlayer space, which is considered a separate reaction zone in photocatalysis, and that hydrogen indeed generates from the aqueous methanol solution rather than from organic components of the derivatives.

Photocatalytic Hydrogen Production from Aqueous Solutions of Glucose and Xylose over Layered Perovskite-like Oxides HCa2Nb3O10, H2La2Ti3O10 and Their Inorganic-Organic Derivatives

“…The organic modification of the protonated oxides was performed in accordance with the methods developed and optimized in our previous reports [ 79 , 80 , 81 ].…”

“…% solutions of D-glucose and D-xylose in water for both bare samples and products of their modification with a 1% Pt cocatalyst under near-ultraviolet irradiation. The measurements were performed on the laboratory photocatalytic setting used in our previous reports [ 78 , 79 , 80 , 81 ] and described in detailes in Supporting Information Figure S1 . The hydrogen formation rate ω, apparent quantum efficiency ϕ , and multiplicity of increase in the rate after Pt loading (platinization increase factor k Pt ) were chosen as quantitative indicators of the photocatalytic performance.…”

“…Despite the wide range of inorganic−organic derivatives synthesized, until recently, any data on their photocatalytic activity towards hydrogen production have been practically absent due to probable concerns about their stability under operating conditions [ 77 ]. However, our recent studies [ 78 , 79 , 80 , 81 ] have shown that oxides HCa 2 Nb 3 O 10 and H 2 Ln 2 Ti 3 O 10 (Ln = La, Nd), preliminarily modified by interlayer n -alkylamines and n -alkoxy groups, demonstrate outstanding photocatalytic performance with regard to light-driven hydrogen evolution from aqueous methanol in the near-ultraviolet range. Particularly, these inorganic−organic derivatives were found to be up to 117 times more active than the unmodified oxides and provide apparent quantum efficiency of more than 40% after additional surface platinization.…”

“…This paper presents the results of the investigation of layered perovskites HCa 2 Nb 3 O 10 , H 2 La 2 Ti 3 O 10 , and their organically modified derivatives as photocatalysts for the conversion of aqueous D-glucose and D-xylose into hydrogen for the first time. The choice of particular inorganic−organic derivatives for photocatalytic tests was based on the results of our previous studies [ 78 , 79 , 80 , 81 ]: for each oxide, we selected one n -alkylamine and one n -alkoxy derivative that demonstrated the highest efficiency of hydrogen evolution from aqueous methanol with a Pt cocatalyst ( n -butylamine and ethoxy derivatives of HCa 2 Nb 3 O 10 , ethylamine and ethoxy ones of H 2 La 2 Ti 3 O 10 ). This study also pays special attention to the influence of Pt reduction conditions on the photocatalytic activity as well as to the role of the oxides’ interlayer space in the hydrogen generation reactions.…”

Hydrogen evolution via noble metals based photocatalysts: A review

“…Hydrogen can also be produced by reforming organic matter derived from renewable biomass [16] [17]. It should be noted that there are other ways to produce hydrogen using solar energy [18]. In addition to the photocatalytic method, photoelectrochemical water splitting [19] and electrolysis techniques [20] have also been used to produce hydrogen.…”