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Ag simultaneously deposited and doped TiO2 (Ag-TiO2) hybrid nanoparticles (NPs) were prepared via a sol-hydrothermal method, as both a sensitive surface-enhanced Raman scattering (SERS) substrate and a superior photocatalyst for the first time. Ag-TiO2 hybrid NPs exhibit excellent SERS performance for several probe molecules and the enhancement factor is calculated to be 1.86 × 105. The detection limit of the 4-mercaptobenzoic acid (4-MBA) probe on the Ag-TiO2 substrate is 1 × 10-9 mol L-1, which is four orders of magnitude lower than that on pure TiO2 as a consequence of the synergistic effects of TiO2 and Ag. This is the highest SERS sensitivity among the reported semiconductor substrates and even comparable to noble metal substrates, and a SERS enhancement mechanism from the synergistic contribution of the semiconductor and noble metal was proposed. And importantly, the Ag-TiO2 hybrid shows excellent photocatalytic degradation activity for the detected species under UV light irradiation at lower concentration conditions, even for the hard to degrade 4-MBA molecule. This makes the Ag-TiO2 hybrid promising as a dual-function platform for both highly sensitive SERS detection and photocatalytic degradation of a pollutant system. Moreover, it also proves that the Ag-TiO2 hybrid can serve as a promising recyclable SERS-active substrate by virtue of its photocatalytic self-cleaning properties for some specific applications, for instance comparative studies of different species on the same SERS platform, in addition to the economic benefit.

We proposed a new ternary nanohybrid rGO–TiO2–Fe3O4 as a magnetically controllable, ultra-sensitive SERS substrate with ultra-high SERS activity and applicability.

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Design and fabrication of highly efficient and stable electrocatalysts remain key challenges in green energy technologies such as low-temperature direct liquid fuel cells. Based on in-depth theoretical calculations, here we demonstrate that surface Pd atoms with high coordination numbers (HCNs) can effectively modulate their adsorption energies for CO and OH, and thus achieve very high performance for formic acid electro-oxidation reaction (FAOR). Based on epitaxial coating Pd atomic layers onto nanoporous gold (NPG) thin membranes and a slight further decoration of Au clusters on top, the resulted core-shell structured NPG-Pd-Au electrocatalyst can demonstrate Pd intrinsic and mass activities of 8.62 mA•cm −2 and 27.25 A•mg −1 respectively at the peak potential around 0.33 V versus saturated calomel electrode toward FAOR, which are far better than those of commercial Pd/C catalysts (1.09 mA•cm −2 and 0.32 A•mg −1 ) tested under the same conditions. Moreover, the membrane electrode assemblies based on these low precious metal loading electrodes can achieve an anode Pd power efficiency over 10 W•mg −1 in a direct formic acid fuel cell, which is two orders of magnitude higher than that of the commercial Pd/C. These results provide new inspirations for the development of revolutionary electrodes for energy technologies in a rational manner.

Design of catalyst layers (CLs) with high proton conductivity in membrane electrode assemblies (MEAs) is an important issue for proton exchange membrane fuel cells (PEMFCs). Herein, an ultrathin catalyst layer was constructed based on Pt-decorated nanoporous gold (NPG-Pt) with sub-Debye-length thickness for proton transfer. In the absence of ionomer incorporation in the CLs, these integrated carbon-free electrodes can deliver maximum mass-specific power density of 198.21 and 25.91 kW•g Pt −1 when serving individually as the anode and cathode, at a Pt loading of 5.6 and 22.0 μg•cm −2 , respectively, comparable to the best reported nano-catalysts for PEMFCs. In-depth quantitative experimental measurements and finite-element analyses indicate that improved proton conduction plays a critical role in activation, ohmic and mass transfer polarizations.