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Practical implementation of CH2Br2 hydrodebromi-nation to CH3Br, an important step in the bromine-mediated functionalization of methane, is currently hindered by the lack of selective and stable catalysts, which typically deactivate over a few hours on stream. Despite ranking as the most active metal for this reaction, palladium has received limited attention due to the tendency of metal nanoparticles to form C2+ products and methane, alongside CH3Br. Herein, we explore metal nuclearity and host effects in nanostructured palladium-based hydrodebromi-nation catalysts. While Pd nanoparticles intrinsically exhibit similar unselective behavior irrespective of the host choice, encompassing metal oxides and carbon-based supports, stabilization of isolated Pd sites over the latter enables suppression of C-C coupling. Therein, the impact of host functionalization and structure on the metal center reactivity is investigated over amorphous activated and nitrogen-doped carbons as well as crystalline carbon nitrides. By maximizing the site architectural uniformity and integrating large N-cavities with high affinity for the metal, we show that high-valent Pd single atoms supported on a poly(triazine imide) carbon nitride unlocks full selectivity to CH3Br (99%) and stable behavior over 24 h on stream. Finally, by combining spectroscopic, kinetic, and computational analyses, we identify that the oxidation state of the metal centers, regulated by the coordination with the host, dictates their thermodynamic propensity to selectively hydrogenate the CH2Br* intermediate to CH3Br. ISSN:2155-5435

Nitrous oxide, N2O, exhibits unique reactivity in oxidation catalysis, but the high manufacturing costs limit its prospective uses. Direct oxidation of ammonia, NH3, to N2O can ameliorate this issue but its implementation is thwarted by suboptimal catalyst selectivity and stability, and the lack of established structure-performance relationships. Systematic and controlled material nanostructuring offers an innovative approach for advancement in catalyst design. Herein low-valent manganese atoms stabilized on ceria, CeO2, are discovered as the first stable catalyst for NH3 oxidation to N2O, exhibiting two-fold higher productivity than the state-of-the-art. Detailed mechanistic, computational and kinetic studies reveal CeO2 as the mediator of oxygen supply, while undercoordinated manganese species activate O-2 and facilitate N2O evolution via N-N bond formation between nitroxyl, HNO, intermediates. Synthesis via simple impregnation of a small metal quantity (1 wt%) predominantly generates isolated manganese sites, while full atomic dispersion is achieved upon redispersion of sporadic oxide nanoparticles during reaction, as confirmed by advanced microscopic analysis and electron paramagnetic resonance spectroscopy. Subsequently, manganese speciation is maintained, and no deactivation is observed over 70 h on stream. CeO2-supported isolated transition metals emerge as a novel class of materials for N2O production, encouraging future studies to evaluate their potential in selective catalytic oxidations at large., Advanced Materials, 35 (24), ISSN:0935-9648, ISSN:1521-4095

Copper catalysts are attractive candidates for Hg-free vinyl chloride monomer (VCM) production via acetylene hydrochlorination due to their non-toxic nature and high stability. However, the optimal architecture for Cu-based catalysts at the nanoscale is not yet fully understood. To address this gap, the metal precursor and the annealing temperature are modified to prepare copper nanoparticles or single atoms, either in chlorinated or ligand-free form, on an unmodified carbon support. Evaluation in the reaction reveals a remarkable convergence of the performance of all materials to the stable VCM productivity of the single-atom catalyst. In-depth characterization by advanced microscopy, quasi in situ and operando spectroscopy, and simulations uncover a reaction-induced formation of low-valent, single atom Cu(I)Cl site motif, regardless of the initial nanostructure. Various surface oxygen groups promote nanoparticle redispersion by stabilizing single-atom CuClx species. The anchoring site structure does not strongly influence the acetylene adsorption energy or the crucial role they play in stabilizing key reaction intermediates. A life-cycle assessment demonstrates the potential environmental benefits of copper catalysts over state-of-the-art alternatives. This work contributes to a better understanding of optimal metal speciation and highlights the sustainability of Cu-based catalysts for VCM production., Advanced Materials, ISSN:0935-9648, ISSN:1521-4095

Chimia, 77 (3), ISSN:0009-4293

Intense efforts have been devoted to developing green and blue centralised Haber-Bosch processes (gHB and bHB, respectively), but the feasibility of a decentralised and more sustainable scheme has yet to be assessed. Here we reveal the conditions under which small-scale systems (NH3-leaves) based on the electrocatalytic reduction of nitrogen (eN(2)R) powered by photovoltaic energy could realise a decentralised scheme competitive in terms of environmental and economic criteria. For this purpose, we calculated energy efficiency targets worldwide, providing clear values that may guide research in the incipient eN(2)R field. Even at this germinal stage, the NH3-leaf technology would compete favourably in sunny locations for CO2-related Earth-system processes and human health relative to the business-as-usual production scenario. Moreover, a modest 8% gain in energy efficiency would already make them outperform the gHB in terms of climate change-related impacts in the sunniest locations. If no CO2 taxation is enforced, the lowest estimated ammonia production cost would be 3 times the industrial standard, with the potential to match it provided a substantial decrease of investment costs and very high selectivity toward ammonia in eN(2)R are achieved. The disclosed sustainability potential of NH3-leaf makes it a strong ally of gHB toward defossilised ammonia production., Energy & Environmental Science, ISSN:1754-5692, ISSN:1754-5706