An experimental study is presented
in which we compare the bulk
phase behavior of discrete and (partially) disperse diblock co-oligomers
(BCOs) with high χ–low N. To this end,
oligomers of dimethylsiloxane (oDMS) and lactic acid
(oLA) were synthesized, each having either a discrete
number of repeat units or a variable block length. Ligation of the
blocks resulted in oDMS–oLA BCOs with dispersities ranging from <1.00001 to 1.09, as revealed
by mass spectroscopy and size exclusion chromatography. The phase
behavior of all BCOs was investigated by differential scanning calorimetry
and small-angle X-ray scattering. Compared to the well-organized lamellae
formed by discrete oDMS–oLA, we observe that an increase in the dispersity of these BCOs results
in (1) an increase of the stability of the microphase-segregated
state, (2) a decrease of the overall degree of ordering, and (3) an increase of the domain spacing.
The catalytic performance of heterogeneous catalysts can be tuned by modulation of the size and structure of supported transition metals, which are typically regarded as the active sites. In single-atom metal catalysts, the support itself can strongly affect the catalytic properties. Here, we demonstrate that the size of cerium dioxide (CeO
2
) support governs the reactivity of atomically dispersed palladium (Pd) in carbon monoxide (CO) oxidation. Catalysts with small CeO
2
nanocrystals (~4 nanometers) exhibit unusually high activity in a CO-rich reaction feed, whereas catalysts with medium-size CeO
2
(~8 nanometers) are preferred for lean conditions. Detailed spectroscopic investigations reveal support size–dependent redox properties of the Pd-CeO
2
interface.
Urea is a commonly used nitrogen fertiliser synthesised from ammonia and carbon dioxide using thermal catalysis. This process results in high CO2 emissions associated with the required amounts of ammonia, Electrocatalysis provides an alternative method to urea production with reduced carbon emissions while utilising waste products like nitrate. This manuscript reports on urea synthesis from the electroreduction of nitrate and carbon dioxide using CuOxZnOy electrodes under mild conditions. Catalysts with different ratios of CuO and ZnO, synthesised via flame spray pyrolysis, were explored for the reaction. The results revealed that all the CuOxZnOy electrocatalyst compositions produce urea, but the efficiency strongly depends on the metal ratio composition of the catalysts. The CuO50ZnO50 composition had the best performance in terms of selectivity (41% at -1.3 V vs Ag/AgCl) and activity (0.27 mA/cm2 at -1.3 V vs Ag/AgCl) towards urea production Thus, this material is within the most efficient electrocatalyst for urea production reported so far. This pioneer study systematically evaluates bimetallic catalysts with varying compositions for urea synthesis from CO2 and nitrate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.