Photocatalytic water splitting at monophasic and biphasic systems

J. RIVA; OLAYA ASTRID; PELJO PEKKA; SMIRNOV EVGENE; VASILOVA NATALIA; BASETTO VICTOR; HUBERT GIRAULT

Bologna

Congreso; 69th Annual Meeting of the International Society of Electrochemistry (ISE); 2018

Inspired by biological photosynthesis, the current research aims to convert sunlight into chemical fuels,by driving the photocatalytic dissociation of water at soft interfaces. The water oxidation reaction is a multi-electron transfer reaction that requires a lot of energy and is considered the most challenging step in water splitting [2].In this work, we study the photoinduced activity of the TTF?+/TTF (tetrathiafulvalene) self-assembled redox shuttle in the water oxidation reaction. Pt microparticles are used as floating electrocatalysts and the redox shuttle is evaluated in two different systems: (I) Monophasic system consisting of water/acetonitrile (ACN) mixtures and (II) a biphasic system formed between water and butyronyrile (BCN), which are inmiscible.In addition, the activity of TTF*+ in the biphasic system was compared with the well known electron acceptor Co(bpy)3 3+ which was recently studied using BiVO4 as the photocatalyst [2]. In the experiments carried out in system (I), TTF/TTF?+(BF4?)x in ACN was vigorously stirred in presence of < 10 μm Pt particles and water, and was irradiated with visible light (455nm). The analysis of the gas phase revealed at first the formation of O2 with 100% efficiency, and eventually H2 evolution. Mass spectrometry and UV-Vis absorption spectroscopy showed no decomposition of the electron acceptorduring the photochemical reaction. Figure 2 shows a scheme of the system (II).Bis(triphenylphosphoranylidene) chloride (BACl) and bis(triphenylphosphoranylidene) tetrakis(pentafluorophenyl)borate (BATB) are the supporting electrolytes in water and butyronitrile phases, respectively. Thus, the cation Bis(triphenylphosphoranylidene) acts as a common ion which induces an specific potential difference across the interface. The evolution rate of O2 is drastically improved under the polarization of the interface with BA+. In this system we analyzed the effect of the Pt particle size, Pt/TTF*+ relationship and BA+ concentration. Conceptually, these two systems represent an approach to solve the energy challenge with minimal environmental impact by using a reversible electron acceptor that allows for a more sustainable watersplitting system.