Assessing the feasibility of reduced graphene oxide as an electronic promoter for photocatalytic hydrogen production over Nb-Ta perovskite photocatalysts

In this work, we explore the feasibility of applying reduced graphene oxide (rGO) as an electronic promoter of the photocatalytic activity of sodium tantalate, sodium niobate, and an intermediate composition for hydrogen evolution. For that purpose, binary metallate/rGO and ternary Pt/metallate/rGO composites have been prepared by a one-pot hydrothermal method followed by the photodeposition of the metal nanoparticles. A considerable improvement in activity is attained with respect to the bare metallates when the ternary system Pt/rGO/metallate is used, depending on the composition of the semiconductor. Thus, composites with NaNbO3 and NaNb0.5Ta0.5O3 fulfil this improvement, but this does not occur with NaTaO3. Opto-electronic and structural-morphological characterizations indicate that a good contact between components is essential for Pt nanoparticles to be deposited on both phases, and this determines the successful photocatalytic performance. This factor, together with appropriate surface chemistry, leads to an optimized activity in the Pt/ NaNb0.5Ta0.5O3/rGO composite.This work has received financial support from the Spanish Ministry of Science, Innovation and Universities through the project SOLPAC (ENE2017-89170-R, MCIU/AEI/FEDER, EU), and from University of Cantabria through the award of a stay of O.I. at IMDEA Energy. Technical assistance by Dr. F. Picó is gratefully acknowledged