@article{10327, abstract = {Composite materials offer numerous advantages in a wide range of applications, including thermoelectrics. Here, semiconductor–metal composites are produced by just blending nanoparticles of a sulfide semiconductor obtained in aqueous solution and at room temperature with a metallic Cu powder. The obtained blend is annealed in a reducing atmosphere and afterward consolidated into dense polycrystalline pellets through spark plasma sintering (SPS). We observe that, during the annealing process, the presence of metallic copper activates a partial reduction of the PbS, resulting in the formation of PbS–Pb–CuxS composites. The presence of metallic lead during the SPS process habilitates the liquid-phase sintering of the composite. Besides, by comparing the transport properties of PbS, the PbS–Pb–CuxS composites, and PbS–CuxS composites obtained by blending PbS and CuxS nanoparticles, we demonstrate that the presence of metallic lead decisively contributes to a strong increase of the charge carrier concentration through spillover of charge carriers enabled by the low work function of lead. The increase in charge carrier concentration translates into much higher electrical conductivities and moderately lower Seebeck coefficients. These properties translate into power factors up to 2.1 mW m–1 K–2 at ambient temperature, well above those of PbS and PbS + CuxS. Additionally, the presence of multiple phases in the final composite results in a notable decrease in the lattice thermal conductivity. Overall, the introduction of metallic copper in the initial blend results in a significant improvement of the thermoelectric performance of PbS, reaching a dimensionless thermoelectric figure of merit ZT = 1.1 at 750 K, which represents about a 400% increase over bare PbS. Besides, an average ZTave = 0.72 in the temperature range 320–773 K is demonstrated.}, author = {Li, Mengyao and Liu, Yu and Zhang, Yu and Han, Xu and Xiao, Ke and Nabahat, Mehran and Arbiol, Jordi and Llorca, Jordi and Ibáñez, Maria and Cabot, Andreu}, issn = {1944-8252}, journal = {ACS Applied Materials and Interfaces}, keywords = {CuxS, PbS, energy conversion, nanocomposite, nanoparticle, solution synthesis, thermoelectric}, number = {43}, pages = {51373–51382}, publisher = {American Chemical Society}, title = {{PbS–Pb–CuxS composites for thermoelectric application}}, doi = {10.1021/acsami.1c15609}, volume = {13}, year = {2021}, } @article{371, abstract = {The design and engineering of earth-abundant catalysts that are both cost-effective and highly active for water splitting are crucial challenges in a number of energy conversion and storage technologies. In this direction, herein we report the synthesis of Fe3O4@NiFexOy core-shell nanoheterostructures and the characterization of their electrocatalytic performance toward the oxygen evolution reaction (OER). Such nanoparticles (NPs) were produced by a two-step synthesis procedure involving the colloidal synthesis of Fe3O4 nanocubes with a defective shell and the posterior diffusion of nickel cations within this defective shell. Fe3O4@NiFexOy NPs were subsequently spin-coated over ITO-covered glass and their electrocatalytic activity toward water oxidation in carbonate electrolyte was characterized. Fe3O4@NiFexOy catalysts reached current densities above 1 mA/cm2 with a 410 mV overpotential and Tafel slopes of 48 mV/dec, which is among the best electrocatalytic performances reported in carbonate electrolyte.}, author = {Luo, Zhishan and Márti Sánchez, Sara and Nafria, Raquel and Joshua, Gihan and De La Mata, Maria and Guardia, Pablo and Flox, Christina and Martínez Boubeta, Carlos and Simeonidis, Konstantinos and Llorca, Jordi and Morante, Joan and Arbiol, Jordi and Ibanez Sabate, Maria and Cabot, Andreu}, issn = {1944-8252}, journal = {Applied Materials and Interfaces}, keywords = {nanoparticle, iron oxide, magnetite, core−shell nanostructure, electrocatalysts, oxygen evolution reaction, OER}, number = {43}, pages = {29461 -- 29469}, publisher = {American Chemical Society}, title = {{Fe3O4@NiFexOy nanoparticles with enhanced electrocatalytic properties for oxygen evolution in carbonate electrolyte}}, doi = {10.1021/acsami.6b09888}, volume = {8}, year = {2016}, } @article{382, abstract = {Mn3O4@CoMn2O4 nanoparticles (NPs) were produced at low temperature and ambient atmosphere using a one-pot two-step synthesis protocol involving the cation exchange of Mn by Co in preformed Mn3O4 NPs. Selecting the proper cobalt precursor, the nucleation of CoxOy crystallites at the Mn3O4@CoMn2O4 surface could be simultaneously promoted to form Mn3O4@CoMn2O4–CoxOy NPs. Such heterostructured NPs were investigated for oxygen reduction and evolution reactions (ORR, OER) in alkaline solution. Mn3O4@CoMn2O4–CoxOy NPs with [Co]/[Mn] = 1 showed low overpotentials of 0.31 V at −3 mA·cm–2 and a small Tafel slope of 52 mV·dec–1 for ORR, and overpotentials of 0.31 V at 10 mA·cm–2 and a Tafel slope of 81 mV·dec–1 for OER, thus outperforming commercial Pt-, IrO2-based and previously reported transition metal oxides. This cation-exchange-based synthesis protocol opens up a new approach to design novel heterostructured NPs as efficient nonprecious metal bifunctional oxygen catalysts.}, author = {Luo, Zhishan and Irtem, Erdem and Ibanez, Maria and Nafria, Raquel and Márti Sánchez, Sara and Genç, Aziz and De La Mata, Maria and Liu, Yu and Cadavid, Doris and Llorca, Jordi and Arbiol, Jordi and Andreu, Teresa and Morante, Joan and Cabot, Andreu}, issn = {1944-8252}, journal = {Applied Materials and Interfaces}, keywords = {nanoparticle, ORR, OER, manganese oxide, cobalt oxide, colloidal, electrocatalysis, cation exchange}, number = {27}, pages = {17435 -- 17444}, publisher = {American Chemical Society}, title = {{Mn3O4@CoMn2O4–CoxOy nanoparticles: Partial cation exchange synthesis and electrocatalytic properties toward the oxygen reduction and evolution reactions}}, doi = {10.1021/acsami.6b02786}, volume = {8}, year = {2016}, }