The photocatalytic performance of nanosized metal (Pt or Pd)-decorated TiO2 nanofibers (NFs) with CdSe quantum dots were tested for activation and reduction of CO2 under UV-B light. The CO2 photoreduction mechanism is proposed to take place via a hydrogenation pathway from first principles calculations. This work was performed in collaboration with the University of Oulu and the Åbo Akademi University, the manuscript is published in the journal of Nano Research.

Anjana Sarkar, Eduardo Gracia-Espino, Thomas Wågberg, Andrey Shchukarev, Melinda Mohl, Anne-Riikka Rautio, Olli Pitkänen, Tiva Sharifi, Krisztian Kordas, Jyri-Pekka Mikkola.
Nano Research, 2016 DOI:10.1007/s12274-016-1087-9

Nanosized metal (Pt or Pd)-decorated TiO2 nanofibers (NFs) were synthesized by a wet impregnation method. CdSe quantum dots (QDs) were then anchored onto the metal-decorated TiO2 NFs. The photocatalytic performance of these catalysts was tested for activation and reduction of CO2 under UV-B light. Gas chromatographic analysis indicated the formation of methanol, formic acid, and methyl formate as the primary products. In the absence of CdSe QDs, Pd-decorated TiO2 NFs were found to exhibit enhanced performance compared to Pt-decorated TiO2 NFs for methanol production. However, in the presence of CdSe, Pt-decorated TiO2 NFs exhibited higher selectivity for methanol, typically producing ∼90 ppmg−1·h−1 methanol. The CO2 photoreduction mechanism is proposed to take place via a hydrogenation pathway from first principles calculations, which complement the experimental observations.

This article has been recently published in the journal Carbon, and here, we report the synthesis C60 nanorods (NRs) and its subsequent decoration with palladium nanoparticles. We modified the NR surface via in situ photochemical transformation in the liquid state, in order to obtain highly stable NRs that retain their crystalline structure during the decoration process. We also show that the photo-transformed C60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity.

Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C60 NRs. Bys measuring the electron mobility of different C60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.

This is our most recent work published in the Journal of American Chemical Society. Here we studied the nanoscale interactions of reduced graphene oxide (rGOx) homogeneously decorated with small palladium nanoclusters (2.3 ± 0.3 nm). The Pd nanoparticles anchored to the rGOx-surface exhibit high crystallinity and are consistent with six-shell cuboctahedral and icosahedral clusters containing ∼600 Pd atoms. We also performed ab initio simulations to understand the electronic properties of the graphene−nanoparticle hybrid system.

This article has been published as an open access, so here you can download the published version of the article.

Studies on noble-metal-decorated carbon nanostructures are reported almost on a daily basis, but detailed studies on the nanoscale interactions for well-defined systems are very rare. Here we report a study of reduced graphene oxide (rGOx) homogeneously decorated with palladium (Pd) nanoclusters with well-defined shape and size (2.3 ± 0.3 nm). The rGOx was modified with benzyl mercaptan (BnSH) to improve the interaction with Pd clusters, and N,N-dimethylformamide was used as solvent and capping agent during the decoration process. The resulting Pd nanoparticles anchored to the rGOx-surface exhibit high crystallinity and are fully consistent with six-shell cuboctahedral and icosahedral clusters containing ∼600 Pd atoms, where 45% of these are located at the surface. According to X-ray photoelectron spectroscopy analysis, the Pd clusters exhibit an oxidized surface forming a PdOx shell. Given the well-defined experimental system, as verified by electron microscopy data and theoretical simulations, we performed ab initio simulations using 10 functionalized graphenes (with vacancies or pyridine, amine, hydroxyl, carboxyl, or epoxy groups) to understand the adsorption process of BnSH, their further role in the Pd cluster formation, and the electronic properties of the graphene−nanoparticle hybrid system. Both the experimental and theoretical results suggest that Pd clusters interact with functionalized graphene by a sulfur bridge while the remaining Pd surface is oxidized. Our study is of significant importance for all work related to anchoring of nanoparticles on nanocarbon-based supports, which are used in a variety of applications.