Dewetting of PtCu Nanoalloys on TiO₂ Nanocavities Provides a Synergistic Photocatalytic Enhancement for Efficient H₂ Evolution

Abstract

We investigate the co-catalytic activity of PtCu alloy nanoparticles for photocatalytic H2 evolution from methanol-water solutions. To produce the photocatalysts, a few nm-thick Pt-Cu bilayers are deposited on anodic TiO2 nanocavity arrays and converted by solid state dewetting, i.e. a suitable thermal treatment, into bimetallic PtCu nanoparticles. XRD and XPS results prove the formation of PtCu nanoalloys that carry a shell of surface oxides. XANES data support Pt and Cu alloying and indicate the presence of lattice disorder in the PtCu nanoparticles. The PtCu co-catalyst on TiO2 shows a synergistic activity enhancement and a significantly higher activity towards photocatalytic H2 evolution than Pt-or Cu-TiO2. We propose the enhanced activity to be due to Pt-Cu electronic interactions, where Cu increases the electron density on Pt favoring a more efficient electron transfer for H2 evolution. In addition, Cu can further promote the photo-activity by providing additional surface catalytic sites for hydrogen recombination. Remarkably, when increasing the methanol concentration up to 50 vol% in the reaction phase, we observe for PtCu-TiO2 a steeper activity increase compared to Pt-TiO2. A further increase in methanol concentration (up to 80 vol%) causes for Pt-TiO2 a clear activity decay, while PtCu-TiO2 still maintains a high level of activity. This suggests an improved robustness of PtCu nanoalloys against poisoning from methanol oxidation products such as CO.

PtCu alloy cocatalysts for efficient photocatalytic CO2 reduction into CH4 with 100% selectivity

“…1c), which is 0.3 eV lower than that for TiO 2 -Pt0Cu1, and the other samples showed the same trend, implying a strong interaction between Pt and Cu and the formation of the PtCu alloy. 43,44 Fig. 1d shows the TEM images of the TiO 2 -Pt0.4Cu0.6 samples.…”

Overcoming Pd–TiO2 Deactivation during H2 Production from Photoreforming Using Cu@Pd Nanoparticles Supported on TiO2

“…Indeed, it has been found that for the Pt–Cu co-catalyst on TiO 2 , it has been observed there is a synergistic activity enhancement and a significantly higher activity toward photocatalytic H 2 evolution with respect to the monometallic Pt– or Cu–TiO 2 catalysts . These authors proposed that the enhanced activity could be due to Pt–Cu electronic interactions, where Cu increases the electron density on Pt, favoring a more efficient electron transfer for H 2 evolution.…”

“…71,72 Indeed, it has been found that for the Pt−Cu co-catalyst on TiO 2 , it has been observed there is a synergistic activity enhancement and a significantly higher activity toward photocatalytic H 2 evolution with respect to the monometallic Pt− or Cu−TiO 2 catalysts. 73 These authors proposed that the enhanced activity could be due to Pt−Cu electronic interactions, where Cu increases the electron density on Pt, favoring a more efficient electron transfer for H 2 evolution. We note that a small amount of Pd incorporated into Cu promotes H adsorption at all coverages examined, while the Cu-core− Pd-shell structure with a significantly higher Pd content promotes HER at moderate hydrogen coverages and is less favorable at the lowest and highest H coverages.…”

Influence of the Electronic Properties of the Ligand on the Photoelectrochemical Behavior of Au25 Nanocluster-Sensitized TiO2 Photoanode

“…Nanoporous TiO 2 arrays were prepared by anodizing a Ti substrate. , Prior to anodization, the titanium samples were degreased by sonication in acetone, ethanol, and deionized water for 15 min in each solvent. The Ti substrates were dried in a nitrogen stream.…”