Photocatalytic reduction of CO2 to valuable chemical fuels is of broad interest, given its potential to activate stable greenhouse CO2 using renewable energy input. We report how to choose the right metal cocatalysts in combination with the surface basicity of TiO2 to enhance their photocatalytic efficiency for CO2 photoreduction. Uniform ligand-free metal nanoparticles (NPs) of Ag, Cu, Au, Pd, and Pt, supported on TiO2, are active for CO2 photoreduction using water as an electron donor. The group XI metals show a high selectivity to CO and Ag/TiO2 is most active to produce CO at a rate of 5.2 μmol g–1 h–1. The group X metals, e.g., Pd and Pt, mainly generate hydrocarbons including methane and ethane, and Pd/TiO2 is slightly more active in methane production at a rate of 2.4 μmol g–1 h–1. The activity of these photocatalysts can be enhanced by varying the surface basicity of TiO2 with primary amines. However, proton reduction selectivity is greatly enhanced in the presence of amine except amine-modified Ag/TiO2, which shows an activity enhancement by 2.4 times solely for CO2 photoreduction as compared to that without amines without switching its selectivity to proton reduction. Using in situ infrared spectroscopy and CO stripping voltammetry, we demonstrate that the improvement of electron density and the low proton affinity of metal cocatalysts are of key importance in CO2 photoreduction. As a systematic study, our results provide a guideline on the right choice of metals in combination of the surface functionality to tune the photocatalytic efficiency of supported metal NPs on TiO2 for selective CO2 photoreduction.

A colloidal-amphiphile-templated growth is developed to synthesize mesoporous complex oxides with highly crystalline frameworks. Organosilane-containing colloidal templates can convert into thermally stable silica that prevents the overgrowth of crystalline grains and the collapse of the mesoporosity. Using ilmenite CoTiO 3 as an example, the high crystallinity and the extraordinary thermal stability of its mesoporosity are demonstrated at 800 °C for 48 h under air. This synthetic approach is general and applicable to a series of complex oxides that are not reported with mesoporosity and high crystallinity, such as NiTiO . Those novel materials make it possible to build up correlations between mesoscale porosity and surfacesensitive physicochemical properties, e.g., electromagnetic response. For mesoporous CoTiO 3 , there is a 3 K increase of its antiferromagnetic ordering temperature, compared with that of nonporous one. This finding provides a general guideline to design mesoporous complex oxides that allow exploring their unique properties different from bulk materials.complex oxides, in general, has associated kinetic barriers from the slow diffusion in solids. [15] When there are two metal cations involved in crystallization of complex oxides like ABO 3 , their nonuniform distribution can result in spontaneous phase separation to form simple oxides. [16] A delicate balance of their sol-gel rates and the precautious control of thermal annealing procedure is needed. On the other hand, ordering competition between the crystallization of oxides and the mesoscale porosity brings profound difficulties to synthesize complex oxides (e.g., perovskites and ilmenites) with mesoporous structures. Crystallization usually leads to the formation of large crystalline grains that will create strong interfacial energies between crystalline walls and pores (e.g., air or templates). For any templated growth of mesoporous oxides using hydrocarbon-based surfactants or block copolymers (BCPs) as soft templates, [17][18][19] mesoscale nanostructures collapse prior to the crystallization of oxides, [20][21][22] because these soft templates are not mechanically strong and thermally stable under elevated temperatures (i.e., >500 °C).Nanostructures show a profound impact on the magnetic properties of materials as well and a few theoretical models have been proposed to understand magnetic behavior of nanoscale particles. [23][24][25][26][27][28][29][30] The magnetic ordering temperature (Curie temperature or Néel temperature) in magnetic materials

Cu-containing metalloenzymes are known to catalyze oxygen activation through cooperative catalysis. In the current work, we report the design of synthetic polymer Cu catalysts using pyrene-labelled poly(2-hydroxy-3-dipicolylamino) propyl methacrylate (Py-PGMADPA) to coordinate multiple Cu sites along polymer chains. The catalysts feature a pyrene end group that can form supramolecular π-π stacking with conductive carbon to allow efficient immobilization of catalysts to the graphite electrode. Cu-containing Py-PGMADPA was examined for electrocatalytic oxygen reduction. The hybrid catalyst showed an onset potential of 0.5 V (vs. RHE) at pH 7 and 0.79 V at pH 13. The kinetic study indicated that the catalyst had a 2e À reduction of oxygen mainly mediated by Cu + centers. We demonstrated the importance of cooperative catalysis among Cu sites which did not exist for other transition metal ions, like Mn 2 + , Fe 2 + , Co 2 + , and Ni 2 +. The confinement of polymer chains promotes the activity and stabilizes Cu catalysts even at an extremely low Cu loading. The rational design of bioinspired polymer catalysts offers an alternative way to prepare synthetic mimics of metalloenzymes.

Control of polymer assemblies in solution is of great importance to determine the properties and applications of these polymer nanostructures. We report a novel co-self-assembly strategy to control the self-assembly outcomes of a micelle-forming amphiphilic block copolymer (BCP) of poly­(ethylene oxide) (PEO) and poly­[3-(trimethoxysilyl)­propyl methacrylate] (PTMSPMA), PEO114-b-PTMSPMA228. With a reactive and hydrophobic additive tetraethyl orthosilicate (TEOS), the assembly nanostructures of PEO114-b-PTMSPMA228 are tunable. The swelling of the PTMSPMA block by hydrophobic TEOS increases the hydrophobic-to-hydrophilic ratio that enables a continuous morphological evolution from spherical micelles to vesicles and eventually to large compound vesicles. TEOS that co-hydrolyzes with the PTMSPMA block can further stabilize and fix these hybrid nanostructures. With high TEOS concentrations, these polymer assemblies can be further converted through thermal annealing into unique silica nanomaterials, including nanospheres, hollow nanoparticles with dual shells, and mesoporous silica frameworks that cannot be synthesized through conventional syntheses otherwise.

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