Particle size and support effects in electrocatalysis and photoelectrochemical water splitting

Abstract

The continued decline in fossil fuel reserves dictates that alternative energy production methods must play an increasing role in our overall energy usage. The generation of hydrogen from photoelectrochemical water splitting has proven itself to be a particularly attractive prospect towards this end. At present, commercial viability of this technology has not been realised due to the large number of stringent material requirements that must be satisfied. One method to improve the efficiency of these cells is through the use of catalysis. The overall effect of catalysts on photoelectrode materials is still relatively unknown. Furthermore, studies of particle size effects and support interactions in this application are seldom reported.
An existing high-throughput methodology [A] was extended towards the synthesis and photoelectrochemical characterisation of metal oxide supported nanoparticles. Pt particles ranging from approximately 1.5 – 6.5 nm in diameter were deposited on both anatase TiO2 and α-Fe2O3. Pt particles reduced the photoelectrochemical performance of TiO2 towards oxygen evolution and methanol photooxidation, with the effect being greater as the Pt particle size increased. Pt had little effect on the photoevolution of oxygen on α-Fe2O3. However, it did bring a significant improvement towards methanol photooxidation, with a specific activity maximum at a particle size of approximately 3 nm. The effects appeared to stem from increased charge separation brought about by Pt. Pt is also ubiquitous as a fuel cell electrocatalyst, in which Pt particle size may have a dramatic effect on cell efficiency. The ORR and MOR were also studied, where in both cases a reduction in specific activity was found as the Pt particle size decreased on both supports. This was particularly apparent on the anatase TiO2 support due to the increased level of rectification and poorer conductivity.
[A] Guerin, S., Hayden, B., Physical Vapour Deposition Method for the High Through-put Synthesis of Solid-State Material Libraries, J. Combi. Chem. 2006, 8, (1), 66-73

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ORCID for Brian Hayden: orcid.org/0000-0002-7762-1812

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