Synthesis of n-Alkoxy Derivatives of Layered Perovskite-Like Niobate HCa2Nb3O10 and Study of Their Photocatalytic Activity for Hydrogen Production from an Aqueous Solution of Methanol

Abstract

A series of hybrid inorganic–organic niobates HCa2Nb3O10×ROH, containing n-alkoxy groups of primary alcohols (R = Me, Et, Pr, Bu, Hx, and Dc) grafted in the interlayer space, has been studied for the first time in relation to photocatalytic hydrogen generation from a model 1 mol % aqueous solution of methanol under ultraviolet irradiation. Photocatalytic activity was measured both for bare samples and for their composites with Pt nanoparticles as a cocatalyst. The advanced measurement scheme allowed monitoring the volume concentration of a sample in a suspension during the experiment, its pH, and possible exfoliation of layered compounds into nanolayers. In the series of n-alkoxy derivatives, the maximum rate of hydrogen evolution was achieved over a Pt-loaded ethoxy derivative HCa2Nb3O10×EtOH/Pt. Its apparent quantum efficiency of 20.6% in the 220–350 nm range was found not to be caused by changes in the light absorption region or specific surface area upon ethanol grafting. Moreover, the amounts of hydrogen released during the measurements significantly exceeded those of interlayer organic components, indicating that hydrogen is generated from the reaction solution rather than from the hybrid material.

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 ].…”

“…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.…”

Recent development of organic–inorganic hybrid photocatalysts for biomass conversion into hydrogen production

“…The hybrid samples seem to be unstable under photocatalytic conditions, and the organic counterpart undergoes degradation during the reaction. 96 Demetra S. Achilleos et al (2020) 97 reported a process that uses carbon dots (CDs) synthesized using the calcination of cellulose, and commercial precursors like aspartic acid or citric acid as the photocatalyst, which absorbs light for lignocellulose conversion into hydrogen and other organic components (Fig. 19).…”

“…18 (a) Crystal structure, and their interlayer distance, (b) TGA curves of the niobates and n-alkoxy derivatives. 96 Copyright 2021, Catalysts.…”