Efficient C-N coupling in electrocatalytic urea generation on copper carbonate hydroxide electrocatalysts

Urea generation through electrochemical CO_(2) and NO_(3)~-co-reduction reaction(CO_(2)NO_(3)RR)is still limited by either the low selectivity or yield rate of urea.Herein,we report copper carbonate hydroxide(Cu_2(OH)_2CO_(3))as an efficient CO_(2)NO_(3)RR electrocatalyst with an impressive urea Faradaic efficiency of45.2%±2.1%and a high yield rate of 1564.5±145.2μg h~(-1)mg_(cat)~(-1).More importantly,H_(2) evolution is fully inhibited on this electrocatalyst over a wide potential range between-0.3 and-0.8 V versus reversible hydrogen electrode.Our thermodynamic simulation reveals that the first C-N coupling follows a unique pathway on Cu_2(OH)_2CO_(3) by combining the two intermediates,~*COOH and~*NHO.This work demonstrates that high selectivity and yield rate of urea can be simultaneously achieved on simple Cu-based electrocatalysts in CO_(2)NO_(3)RR,and provide guidance for rational design of more advanced catalysts.

Interatomic diffusion in Pd-Pt core-shell nanoparticles

Pt monolayer-based core-shell catalysts have garnered significant interest for the application of low temperature fuel cell technology as their use may enable a decreased loading of Pt while still providing sufficient current density to meet volumetric requirements. One promising candidate in this class of materials is a Pd@Pt core-shell catalyst, which shows enhanced activity toward oxygen reduction reaction(ORR). One concern with the use of Pd@Pt, however, is the durability of the core-shell structure as Pd atoms are thermodynamically favored to migrate to the surface. The pathway of the migration has not been systematically studied. The current study explores the stability of this structure to thermal annealing and probes the effect of this heat treatment on the catalyst surface structure and its oxygen reduction activity. It was found that surface alloying between Pd and Pt occurs at temperatures as low as 200 °C, and significantly alters the structure and ORR catalytic activity in the range of 200–300 °C. Our results shed lights on the thermal induced interatomic diffusion in all core-shell and thin film structures.

Metal organic framework‐ionic liquid hybrid catalysts for the selective electrochemical reduction of CO_(2) to CH4

The electrochemical reduction of CO_(2) towards hydrocarbons is a promising technology that can utilize CO_(2) and prevent its atmospheric accumulation while simultaneously storing renewable en‐ergy.However,current CO_(2) electrolyzers remain impractical on a large scale due to the low current densities and faradaic efficiencies(FE)on various electrocatalysts.In this study,hybrid HKUST‐1 metal‐organic framework‒fluorinated imidazolium‐based room temperature ionic liquid(RTIL)electrocatalysts are designed to selectively reduce CO_(2) to CH_(4).An impressive FE of 65.5%towards CH_(4) at-1.13 V is achieved for the HKUST‐1/[BMIM][PF_(6)]hybrid,with a stable FE greater than 50%maintained for at least 9 h in an H‐cell.The observed improvements are attributed to the increased local CO_(2) concentration and the improved CO_(2)‐to‐CH_(4) thermodynamics in the presence of the RTIL molecules adsorbed on the HKUST‐1‐derived Cu clusters.These findings offer a novel approach of immobilizing RTIL co‐catalysts within porous frameworks for CO_(2) electroreduction applications.

Pt-Ni nanourchins as electrocatalysts for oxygen reduction reaction

Pt-Ni bimetallic alloys with various nanos-tructures have shown excellent activity toward oxygen reduction reaction （ORR）. The ORR activity is highly dependent on the structure of the catalyst. In this paper, Pt-Ni nanourchins were synthesized with an average size of 50 nm consisting of 10-20 nanorods and nanooctahedra by adjusting the synthesis condition. The formation of Pt-Ni nanourchins is mainly dependent on the adding order of solvents （benzyl ether, oleylamine and oleic acid）. Pt-Ni nanourchins present a reasonable high ORR activity （0.81 A/mg at 0.9 V）.

Organic frameworks confined Cu single atoms and nanoclusters for tandem electrocatalytic CO_(2) reduction to methane

The electrochemical reduction reaction of carbon dioxide(CO_(2)RR)is considered to be an effective way to realize carbon neutrality.As a type of intensively studied materials,covalent organic frameworks(COFs)with a tunable pore structure and various functional groups are promising catalysts for CO_(2)RR.Herein,COF synthesized by 2,6‐diaminoanthraquinone and 2,4,6‐triformylphloroglucinol is employed to assist the synthesis of electrocatalysts from Cu single atoms(SAs)to nanoclusters by controlling the electrodeposition.A tandem catalyst for CO_(2)‐to‐CH4 conversion is thus achieved by the Cu nanoclusters dispersed among the isolated Cu SAs in the COF network.It is proposed that CO_(2) is first reduced to CO over the atomically isolated Cu SAs,followed by diffusion onto the neighboring Cu nanoclusters for further reduction into CH4.In addition,mechanistic analysis suggests that the coordinated K^(+)ions on the COF network promote the activation of CO_(2) and the adsorption of reaction intermediates,thus realizing the suppressed hydrogen evolution reaction and selective production of CH4.This study presents a new insight of COFs for the confined synthesis of a tunable SA to nanocluster electrocatalysts,disclosing the great potential of COFs in electrocatalysis.