Tailoring Zirconia Supported Intermetallic Platinum Alloy via Reactive Metal-Support Interactions for High-Performing Fuel Cells.

Developing efficient and anti-corrosive oxygen reduction reaction (ORR) catalysts is of great importance for the applications of proton exchange membrane fuel cells (PEMFCs). Herein, we report a novel approach to prepare metal oxides supported intermetallic Pt alloy nanoparticles (NPs) via the reactive metal-support interaction (RMSI) as ORR catalysts, using Ni-doped cubic ZrO2 (Ni/ZrO2) supported L10-PtNi NPs as a proof of concept. Benefiting from the Ni migration during RMSI, the oxygen vacancy concentrations in the support are increased, leading to an electron enrichment of Pt. The optimal L10-PtNi-Ni/ZrO2-RMSI catalyst achieves remarkably low mass activity (MA) loss (17.8 %) after 400,000 accelerated durability test cycles in a half-cell and exceptional PEMFC performance (MA=0.76 A mgPt -1 at 0.9 V, peak power density=1.52/0.92 W cm-2 in H2-O2/-air, and 18.4 % MA decay after 30,000 cycles), representing the best reported Pt-based ORR catalysts without carbon supports. Density functional theory (DFT) calculations reveal that L10-PtNi-Ni/ZrO2-RMSI requires a lower energetic barrier for ORR than L10-PtNi-Ni/ZrO2 (direct loading), which is ascribed to a decreased Bader charge transfer between Pt and *OH, and the improved stability of L10-PtNi-Ni/ZrO2-RMSI compared to L10-PtNi-C can be contributed to the increased adhesion energy and Ni vacancy formation energy within the PtNi alloy.

Regulating the Coordination Environment of Single-Atom Catalysts Anchored on Thiophene Linked Porphyrin for an Efficient Nitrogen Reduction Reaction.

The electrochemical nitrogen reduction reaction (NRR) offers a promising strategy to resolve high energy consumption in the nitrogen industry. Recently, the regulation of the electronic structure of single-atom catalysts (SACs) by adjusting their coordination environment has emerged as a rather promising strategy to further enhance their electrocatalytic activity. Herein, we design novel SACs supported by thiophene-linked porphyrin (TM-N4/TP and TM-N4-xBx/TP, where TM = Sc to Au) as potential NRR catalysts using density functional theory calculations. Among these catalysts, TM-N4/TP (TM = Ti, Nb, Mo, Ta, W, and Re) and TM-N4/TP with a water bilayer (TM = Nb, Mo, W, and Re) show excellent activity (low limiting potential) but low selectivity. Encouragingly, we find that Mo-N3B/TP, Mo-N2B2-2/TP, W-N3B/TP, W-N2B2-2/TP, Re-N3B/TP, Re-N2B2-2/TP, and Re-N2B2-1/TP serve as the most efficient NRR electrocatalysts, as they present stability, superior activity, better selectivity with low limiting potentials (-0.18 ∼ -0.90 V), and high Faradaic efficiencies (>99.80%). Based on microkinetic modeling, kinetic analysis of the NRR is performed and shows that the Re-N2B2-1/TP catalyst is more efficient for NH3 formation. Additionally, multiple-level descriptors provide insight into the origin of NRR activity and enable fast prescreening among numerous candidates. This work provides a new perspective to design highly efficient catalysts for the NRR under ambient conditions.

Hydrogen-Bond-Donor-Directed Switching of Enantioselectivity in the Vinylogous Aldol-Cyclization Cascade Reaction of Prostereogenic 3-Alkylidene Oxindoles with Isatins and o-Quinones.

In this study, we reported a hydrogen-bond-donor-directed enantiodivergent vinylogous aldol-cyclization cascade reaction of 3-alkylidene oxindoles with isatins and o-quinones. Both enantiomers can be prepared by thiourea or squaramide cinchona alkaloid bifunctional organocatalysts with the same quinine scaffold. Kinetic study data provided the possible reaction mechanism for the vinylogous aldol-cyclization cascade reaction. The DFT calculation data showed the geometry of the generated dienolates from pronucleophiles dominated the observed switch of enantioselectivity.

Enantioselective Organocatalytic Three-Component Vinylogous Michael/Aldol Tandem Reaction among 3-Alkylidene oxindoles, Methyleneindolinones, and Aldehydes.

We reported a one-pot enantioselective three-component vinylogous Michael/aldol tandem reaction of prochiral 3-alkylidene oxindoles with methyleneindolinones and aldehydes using bifunctional organocatalysts. A variety of enantioenriched 3,3-disubstituted oxindoles 3 and spirolactones 4 were generated in moderate yields (up to 78%) with high stereoselectivities (up to >20:1 dr, >99% ee). Intriguingly, we observed that the aldol reaction with paraformaldehyde generates 3,3-disubstituted oxindoles 3 bearing a hydroxymethyl group, while the reaction with aliphatic aldehydes generates spirolactones 4.

Synthesis, density functional theory (DFT) studies and urease inhibition activity of chiral benzimidazoles.

A variety of benzimidazole by the heterocyclization of orthophenylenediamine were synthesized in 69-86% yields. The synthesized compounds 3a-f and 6a-f were characterized and further investigated as jack bean urease inhibitors. Density functional theory (DFT) studies were performed utilizing the basis set B3LYP/6-31G (d, p) to acquire perception into their structural properties. Frontier molecular orbital (FMO) analysis of all compounds 3a-f and 6a-f was computed at the same level of theory to get a notion about their chemical reactivity and stability. The mapping of the molecular electrostatic potential (MEP) over the entire stabilized molecular geometry indicated the reactive centers. They exhibited urease inhibition activity with IC50 between 22 and 99 µM. Compounds containing withdrawing groups on the benzene ring (3d, 6d) were not showing significant urease inhibition. The value obtained for 3a, 3b, 3f had shown their significant urease inhibition for both theoretical and experimental. Notably, the compound having S-configuration (3a) (22.26 ± 6.2 µM) was good as compared to its R enantiomer 3f (31.42 ± 23.3 µM). Despite this, we elaborated the computational studies of the corresponding compounds, to highlight electronic effect which include HOMO, LUMO, Molecular electrostatic potential (MEP) and molecular docking.