A one-step ligand-free method based on an adsorption-precipitation process was developed to fabricate iridium/cerium oxide (Ir/CeO ) nanocatalysts. Ir species demonstrated a strong metal-support interaction (SMSI) with the CeO substrate. The chemical state of Ir could be finely tuned by altering the loading of the metal. In the carbon dioxide (CO ) hydrogenation reaction it was shown that the chemical state of Ir species-induced by a SMSI-has a major impact on the reaction selectivity. Direct evidence is provided indicating that a single-site catalyst is not a prerequisite for inhibition of methanation and sole production of carbon monoxide (CO) in CO hydrogenation. Instead, modulation of the chemical state of metal species by a strong metal-support interaction is more important for regulation of the observed selectivity (metallic Ir particles select for methane while partially oxidized Ir species select for CO production). The study provides insight into heterogeneous catalysts at nano, sub-nano, and atomic scales.

The manipulation of crystal orientation from the thermodynamic equilibrium states is desired in layered hybrid perovskite films to direct charge transport and enhance the perovskite devices performance. Here we report a templated growth mechanism of layered perovskites from 3D-like perovskites which can be a general design rule to align layered perovskites along the out-of-plane direction in films made by both spin-coating and scalable blading process. The method involves suppressing the nucleation of both layered and 3D perovskites inside the perovskite solution using additional ammonium halide salts, which forces the film formation starts from solution surface. The fast drying of solvent at liquid surface leaves 3D-like perovskites which surprisingly templates the growth of layered perovskites, enabled by the periodic corner-sharing octahedra networks on the surface of 3D-like perovskites. This discovery provides deep insights into the nucleation behavior of octahedra-array-based perovskite materials, representing a general strategy to manipulate the orientation of layered perovskites.

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Removing excess nitrate (NO3 –) from waste streams has become a significant environmental and health topic. However, realizing highly selective NO3 – conversion toward N2, primarily via electrocatalytic conversions, has proven challenging, largely because of the kinetically uncontrollable NO3 –-to-NO2 – pathway and unfavorable N–N coupling. Herein, we discovered unique and ultra-high electrocatalytic NO3 –-to-NO2 –activity on oxide-derived silver (OD-Ag). Up to 98% selectivity and 95% Faradaic efficiency (FE) of NO2 – were observed and maintained under a wide potential window. Benefiting from the superior NO3 –-to-NO2 –activity, further reduction of accumulated NO2 – to NH4 + was well regulated by the cathodic potential and achieved an NH4 + FE of 89%, indicating a tunable selectivity to the key nitrate reduction products (NO2 – or NH4 +) on OD-Ag. Density functional theory computations provided insights into the unique NO2 – selectivity on Ag electrodes compared with Cu, showing the critical role of a proton-assisted mechanism. Based on the ultra-high NO3 –-to-NO2 – activity on OD-Ag, we designed a novel electrocatalytic–catalytic combined process for denitrifying real-world NO3 –-containing agricultural wastewater, leading to 95+% of NO3 – conversion to N2 with minimal NOX gases. In addition to the wastewater treatment process to N2 and the electrochemical synthesis of NH3, NO2 – derived from electrocatalytic NO3 – conversion can serve as a reactive platform for the distributed production of various nitrogen products.