The influence of ammonia (NH 3) on the doubly deuterated formic acid (DCOOD, FA) dehydrogenation selectivity for a Pd(111) single crystal model catalyst surface was investigated under ultrahigh vacuum conditions using temperature-programmed desorption and temperatureprogrammed reaction spectroscopy techniques. NH 3 adsorption on Pd(111) revealed reversible, molecular desorption without any significant decomposition products, while DCOOD adsorption on Pd(111) yielded D 2 , D 2 O, CO, and CO 2 as a result of dehydration and dehydrogenation pathways. Functionalizing the Pd(111) surface with ammonia suppressed the FA dehydration and enhanced the dehydrogenation pathway. The boost in the FA dehydrogenation of Pd(111) in the presence of NH 3 can be linked to the ease of FA deprotonation as well as the stabilization of the decomposition intermediate (i.e., formate) due to the presence of ammonium counterions on the surface. In addition, the presence of a Hbonded ammonia network on the Pd(111) surface increased the hydrogen atom mobility and decreased the activation energy for molecular hydrogen desorption. In the presence of NH 3 , catalytic FA decomposition on Pd(111) also yielded amidation reactions, which further suppressed CO liberation and prevented poisoning of the Pd(111) active sites due to strongly bound CO species.

Functionalization of TiO2 (P25) with oleic acid‐capped CdSe(core)/CdSeTe(crown) quantum‐well nanoplatelets (NPL) yielded remarkable activity and selectivity toward nitrate formation in photocatalytic NOx oxidation and storage (PHONOS) under both ultraviolet (UV‐A) and visible (VIS) light irradiation. In the NPL/P25 photocatalytic system, photocatalytic active sites responsible for the NO(g) photo‐oxidation and NO2 formation reside mostly on titania, while the main function of the NPL is associated with the photocatalytic conversion of the generated NO2 into the adsorbed NO3− species, significantly boosting selectivity toward NOx storage. Photocatalytic improvement in NOx oxidation and storage upon NPL functionalization of titania can also be associated with enhanced electron‐hole separation due to a favorable Type‐II heterojunction formation and photo‐induced electron transfer from the CdSeTe crown to the CdSe core of the quantum well system, where the trapped electrons in the CdSe core can later be transferred to titania. Re‐usability of NPL/P25 system was also demonstrated upon prolonged use of the photocatalyst, where NPL/P25 catalyst surpassed P25 benchmark in all tests.

The influence of MnO x overlayers/nanoclusters deposited on the Pd(111) single-crystal model catalyst surface on the catalytic dehydrogenation of double-deuterated formic acid (FA, DCOOD) was studied under ultrahigh vacuum conditions via temperature-programmed desorption and X-ray photoelectron spectroscopy techniques. A significant boost in D 2 generation was observed in the catalytic FA dehydrogenation on MnO x /Pd(111) as compared to that of a clean Pd(111) model catalyst, demonstrating the cooperative interaction between Pd(111) and MnO x sites. Maximum FA conversion was observed at a submonolayer MnO x surface coverage of 0.25 ML (monolayer) on Pd(111), whereas D 2 formation was found to be suppressed when the Pd(111) surface was entirely covered with relatively thick (15 ML) MnO x overlayers. A direct correlation between increasing relative abundance of oxidized Mn surface states (i.e., Mn 2+ , Mn 3+ , and Mn 4+ ) and increasing catalytic FA dehydrogenation was observed. Different modes of promotion of FA dehydrogenation via MnO x (i.e., catalytic promotion versus noncatalytic/stoichiometric promotion) were discussed as a function of the differences in the model catalyst preparation and the extent of oxidation of the MnO x overlayer.

Understanding the activation of CO 2 on the surface of the heterogeneous catalysts comprised of metal/metal oxide interfaces is of critical importance since it is not only a prerequisite for converting CO 2 to value-added chemicals but also often, a rate-limiting step. In this context, our current work focuses on the interaction of CO 2 with heterogeneous bi-component model catalysts consisting of small MnO x clusters supported on the Pd(111) single crystal surface. These metal oxide-on-metal 'reverse' model catalyst architectures were investigated via temperature programmed desorption (TPD) and x-ray photo-electron spectroscopy (XPS) techniques under ultra-high vacuum (UHV) conditions. Enhancement of CO 2 activation was observed upon decreasing the size of MnO x nanoclusters by lowering the preparation temperature of the catalyst down to 85 K. Neither pristine Pd(111) single crystal surface nor thick (multilayer) MnO x overlayers on Pd(111) were not capable of activating CO 2 , while CO 2 activation was detected at submonolayer (~0.7 ML) MnO x coverages on Pd(111), in correlation with the interfacial character of the active sites, involving both MnO x and adjacent Pd atoms.