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The electrocatalyzed ammonia oxidation reaction (AOR) is an ambient temperature and pressure process with potential applications for sustainable energy generation and waste ammonia treatment. In this work, we study the mechanism of ammonia oxidation toward N2, NO2–, and NO3–on the (0001)β-NiOOH surface and compare the computed free energy of reaction intermediates to results previously obtained on (0001) β-Ni(OH)2. NiOOH surfaces with a hydroxide vacancy favored NH2–NH2coupling and reduced the theoretical onset potential for N2, NO2–, and NO3–formation relative to the β-Ni(OH)2surface. The surface with an oxygen vacancy favored NH–NH coupling and had lower onset potentials for N2and NO2–formation relative to the β-Ni(OH)2surface, while NO3–formation was slightly hindered due to its increased stabilization of the precursor adsorbate, *NO2. In general, the NiOOH surface had lower computed onset potentials compared to the Ni(OH)2surface due to the destabilization of certain adsorbates which form thermodynamic sinks in the AOR pathway, leading to differences in the potential-determining step for the formation of N2and NO2–.

Programmable dynamic catalysts provide a promising means to break linear scaling relations and exceed theoretical Sabatier volcano performance peaks. In this issue of Chem Catalysis, Gathmann et al. demonstrate how reactions can attain greater turnover frequency enhancements if the energies of consecutive intermediates are shifted in opposite directions to an external perturbation.

The ammonia oxidation reaction (AOR) has applications as a sustainable energy source and in wastewater remediation. Nickel based catalysts for the AOR reaction are ideal as they are cost efficient, have longer lifetimes than more expensive alternatives, and can produce value-added products. Dopants can be applied to these nickel catalysts to further increase their value. This work explores the effects on reaction potentials when β-Ni(OH)2is doped with chromium, cobalt, copper, or iron using density functional theory to model the AOR. Limiting potentials for dinitrogen production improved when β-Ni(OH)2was doped with chromium and cobalt. Limiting potentials for nitrite production remained consistent when β-Ni(OH)2was doped with cobalt or iron. Compared with the pristine β-Ni(OH)2surface, there was no improvement in the limiting potential of nitrate formation for any of the doped surfaces. This research begins to reveal the importance of exploring dopant addition to β-Ni(OH)2as a method of improving the catalyst activity for the AOR.

Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest. Surface-patterned particles act as colloidal analogues of atoms and molecules, serve as model systems in studies of phase transitions in liquid systems, behave as ‘colloidal surfactants’ and function as templates for the synthesis of hybrid particles. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient, but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties. At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles, and nanoparticles with surface ripples or a ‘raspberry’ surface morphology. Here we demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. These patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization.

Herein, we report on the facile synthesis of nanocomposite consisting of TiO2and Au nanoparticles (NPs) via a tailored galvanic replacement reaction (GRR). The electrocatalytic activity of the synthesized TiO2/Au nanocomposites for CO2reduction was investigated in an aqueous solution using various electrochemical methods. Our results demonstrated that the TiO2/Au nanocomposites formed through the GRR process exhibited improved catalytic activities for CO2reduction, while generating more hydrocarbon molecules than the typical formation of CO in contrast to polycrystalline Au. GC analysis and NMR spectroscopy revealed that CO and CH4were the gas products, whereas HCOO–, CH3COO–, CH3OH, and CH3CH2OH were the liquid products from the CO2reduction at different cathodic potentials. This remarkable change was further studied using the density functional theory (DFT) calculations, showing that the TiO2/Au nanocomposites may increase the binding energy of the formed ·CO intermediate and reduce the free energy compared to Au, thus favoring the downstream generation of multicarbon products. The TiO2/Au nanocomposites have high catalytic activity and excellent stability and are easy to fabricate, indicating that the developed catalyst has potential application in the electrochemical reduction of CO2to value-added products.