Oxide-derived copper is known for its unique ability to catalyze the selective electroreduction of CO2 to C2 and higher carbon compounds at low overpotentials. To understand this phenomenon, mechanistic studies typically chose ethylene (C2H4) as the model compound. The pathways to form other C2 compounds such as ethane (C2H6) and ethanol are then generally considered to be similar to that of C2H4. However, regular detection of C2H6 or ethanol on thick oxide-derived Cu at low overpotentials, often with selectivities exceeding that of C2H4, raises an important question: does the formation of these two C2 molecules really share a common route with C2H4? In this work, through an investigation of CO2 electroreduction on oxide-derived Cu of different thicknesses and oxidation states, we show that the formation of C2H6 and ethanol on thick oxide-derived Cu films could proceed through routes distinct from that of C2H4 at low overpotentials. Investigations using select molecular precursors such as diacetyl [(CH3CO)2] suggest that the formation of C2H6 on thick oxide-derived Cu surfaces is likely to originate from the dimerization of −CH3 intermediates. We attribute the higher selectivity for C2H6 and ethanol to a higher population of Cu+ sites in the thick oxide-derived Cu films, which helped to stabilize the −CH3 intermediates.

The successful design and synthesis of earth-abundant and efficient catalysts for the oxygen evolution reaction (OER) will be a major step forward towards the use of electrochemical water splitting as an environmental-friendly process for producing H2 fuel. Due to their poor activity, copper-based materials have not been considered apt for catalysing OER. In this work, we demonstrate that unique copper (II) oxide nanostructures obtained via hydrothermal synthesis and subsequent hydrogen peroxide treatment exhibit unusually high and sustainable OER activity. In 0.1 M KOH electrolyte, the CuO nanostructures catalyse OER with currents at 2.6-3.4 mA cm -2 at 1.75 V (vs. RHE). The calculated turnover frequency (per Cu site) of ∼2×10 -3 s -1 for O2 production is markedly higher than that of high-surface area electrodeposited Cu metal nanoparticles by 40-68 times. The OER activity of the CuO nanostructures is also stable, approaching about half of 20% IrOx/Vulcan XC-72 after an hour long OER. In-situ Raman spectroscopy at OER-relevant potentials recorded compelling evidence that Cu III active species may be responsible for the unusual OER activity of the CuO nanostructures, as indicated by its signature vibration at 603 cm -1 . This hitherto unobserved peak is assigned, with the aid of the model compound NaCu III O2, to the Cu-O stretching vibration of Cu III oxide. This feature was not found on electrodeposited Cu metal, which exhibited correspondingly weaker OER activity. The enhanced catalysis of O2 evolution by the CuO nanostructures is thus attributed to not just its higher surface area, but also to the higher population of Cu III active sites on its surface.

The catalytic activity of a series of neutral and cationic, homo- and heteroleptic, mono- and bimetallic palladium(II) compounds based on dithiocarbamate and dithiooxamide S,S-donor ligands is described. High activity was observed in the regio- and chemo-selective C–H functionalization of benzo[h]quinoline to 10-alkoxybenzo[h]quinoline and 8-methylquinoline to 8-(methoxymethyl)quinoline in the presence of the oxidant PhI(OAc)2. The best performance was found for [Pd(Me2dazdt)2]I6 (Me2dazdt = N,N′-dimethyl-perhydrodiazepine-2,3-dithione), [PdI2(Me2dazdt)] and [Pd(Cy2DTO)2]I8 (Cy2DTO = N,N′-dicyclohexyl-dithiooxamide) which are all obtained directly as products of sustainable Pd-metal leaching processes used to recover palladium from scrap metal. These compounds provided almost quantitative yields under milder conditions (50 °C, 1–3 mol% Pd loading) and much shorter reaction times (1–3 h) than reported previously. These results illustrate how the complexes obtained from the selective and sustainable recovery of Pd from automotive heterogeneous Three Way Catalysts (TWC) can be employed directly in homogeneous catalysis, avoiding further metal recovery steps and valorising the metal complex itself in a ‘circular economy’ model

Upon Sr-doping in GdBa1−xSrxCo2O6−δ, a shift of the valence band maximum VBmax towards the Fermi energy EF was observed leading to better OER activity.

PdI2(Me2dazdt)] is obtained from palladium powder via a 100% atom economical Pd(0) leaching reaction using Me2dazdt (N,N'-dimethyl-perhydrodiazepine-2,3-dithione) and iodine. This complex is a versatile starting point for ligand exchange reactions with (di)phosphines, yielding trans-[PdI2(PPh3)2] and [PdI2(dppe)] (dppe = 1,2-bis(diphenylphosphino)ethane). Further reaction with dithiocarbamates provides compounds of the form [Pd(DTC)(L)n]+ (DTC = dithiocarbamate; L = PPh3, n = 2; L = dppe, n = 1), which are highly active catalysts for regioand chemo-selective C-H bond activation reactions. Using DTC ligands with trimethoxysilyterminated tethers, the palladium(II) units can be attached to the surface of core-shell, silicacoated Fe3O4 nanoparticles. Once tethered, these units formed the catalytically-active component of a recyclable, quasi-heterogeneous, Pd(II)-based catalytic system based on recovered palladium, illustrating the proposed circular model strategy. These investigations contribute to key steps in this process, such as efficient, atom-economical recovery, chemoselectivity of ligand substitution reactions, demonstration of catalytic activity and the potential for immobilization of catalytic surface units derived from recovered metal.