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The present review describes electrochemical methods for the recovery of chemical feedstocks from waste materials. We emphasize the use of electrical current, fields, and controlled potentials as sustainable, scalable solutions to impending societal challenges such as materials recycling and the management of solid wastes. This review focuses on two facets of electrochemical recycling: (1) the recovery of critical raw materials from wastes that would otherwise be destined for landfills and (2) the recycling and upcycling of waste polymer streams. This review describes both technological processes and current research with the goal of catalyzing understanding towards the mining of valuable materials from complex wastes.

This work reports the first example of mono-nuclear Cu pincers with SNS ligation acting as electrocatalyst precursors for the electrochemical conversion of carbon dioxide to CO and H2 in protic organic media.

This work examines the relative reactivities of ReI and MnI tricarbonyl pyridine-2,6-bis-N-heterocyclic carbene pincers M(CO)3CNCBnX (M = Re, Mn and X = Cl and Br) towards catalysis for the electrochemical conversion of CO2 to CO. Unlike prior well-studied group VII catalysts, Mn(CO)3CNCBnX is extraordinarily active, while the new Re(CO)3CNCBnX complex surprisingly does not exhibit catalytic response. DFT calculations shed light on this puzzling behavior and show that the redox-active pyridine-2,6-bis-N-heterocyclic carbene ligand facilitates the reduction of the ground-state complexes; however, the extent of electronic delocalization in the reduced intermediates differs in the degree of metalloradical character. The highly-active Mn(CO)3CNCBnX complex proceeds through an intermediate with nucleophilic metalloradical character in which 66% of the unpaired electron spin resides on Mn. In contrast, Re(CO)3CNCBnX reduction proceeds through an intermediate with less metalloradical character in which only 38% of the unpaired spin is localized on Re with the remainder delocalized over the ligand. The energetic penalty of the electron delocalization of an electron on the ligand affects the M-CO bond strengths and related kinetic barriers. We discuss these observations in the context of turnover-enabling effects in CO2 reductions mediated by group VII NHC pincer molecular electrocatalysts.

The decrease of total amount of atmospheric CO2 is an important societal challenge in which CO2 reduction has an important role to play. Electrocatalytic CO2 reduction with homogeneous catalysts is based on highly tunable catalyst design and exploits an abundant C1 source to make valuable products such as fuels and fuel precursors. These methods can also take advantage of renewable electricity as a green reductant. Mn-based catalysts offer these benefits while incorporating a relatively cheap and abundant first-row transition metal. Historically, interest in this field started with Mn(bpy-R)(CO)3X, whose performance matched that of its Re counterparts while achieving substantially lower overpotentials. This review examines an emerging class of homogeneous Mn-based electrocatalysts for CO2 reduction, Mn complexes with meridional tridentate coordination also known as Mn pincers, most of which contain redox-active ligands that enable multi-electron catalysis. Although there are relatively few examples in the literature thus far, these catalysts bring forth new catalytic mechanisms not observed for the well-established Mn(bpy-R)(CO)3X catalysts, and show promising reactivity for future studies.

This work examines the relative reactivities of Re

We report the synthesis, characterization, and catalytic CO2 reduction activity of two LMn(CO)3Br complexes with carbene-pyridine-carbene pincer ligands, [MnCNCMe]Br 1 and [MnCNCBn]Br (Bn = benzyl) 2. X-ray crystallography reveals an octahedral coordination environment with an outer sphere Br anion for 1. Catalyst 2 performs the reduction of CO2 to CO at 100 mV more positive potential with similar current densities as 1. We hypothesize the bulkier benzyl arms on the pincer hinder formation of a dimer. They also alter the wingtip electronics, enabling operation at a lower overpotential. We use normal pulse voltammetry and diffusion ordered spectroscopy to quantify a 1e– reduction per manganese center at the catalytic onset. We now show turnover even in the absence of added protons..