Electrochemical Metal Recycling: Recovery of Palladium from Solution and In Situ Fabrication of Palladium-Carbon Catalysts via Impact Electrochemistry

Abstract

Recycling of critical materials, regeneration of waste, and responsible catalyst manufacture have been repeatedly documented as essential for a sustainable future with respect to the environment and energy production. Electrochemical methods have become increasingly recognized as capable of achieving these goals, and "impact" electrochemistry, with the advantages associated with dynamic nanoelectrodes, has recently emerged as a prime candidate for the recovery of metals from solution. In this report, the nanoimpact technique is used to generate carbon-supported palladium catalysts from low-concentration palladium(II) chloride solutions (i.e., a waste stream mimic) as a proof of concept. Subsequently, the catalytic properties of this material in both synthesis (Suzuki coupling reaction) and electrocatalysis (hydrogen evolution) are demonstrated. Transient reductive impact signals are shown and analyzed at potentials negative of +0.4 V (vs SCE) corresponding to the onset of palladium deposition in traditional voltammetry. Direct evidence of Pd modification was obtained through characterization by environmental scanning electron microscopy/energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis of impacted particles. This showed the formation of deposits of Pd0 partially covering the 50 nm carbon black particles with approximately 14% Pd (wt %) under the conditions used. This material was then used to demonstrate the conversion of iodobenzene into its biphenyl product (confirmed through nuclear magnetic resonance) and the successful production of hydrogen as an electrocatalyst under acidic conditions (under cyclic voltammetry).

High-Performance Polyimides Derived from Biomass: Design, Synthesis, and Properties

“…4,4′-Oxydiphthalic anhydride (0.6515 g, 0.0021 mol) was, respectively, mixed with daidzein-based diamine (0.8729 g, 0.002 mol) and 4,4′-diaminodiphenyl ether (0.4004 g, 0.002 mol), and the preparation process was the same as that above (called PI-O-D and PI-O-O). In particular, the solvent DMF used in the synthesis process, as well as the Pd/C catalyst in the synthesis of diamine monomer, can be recycled and reused in industrial production. , …”

“…The crude product was recrystallized three times in ethanol to obtain the daidzein-based diamine (Figures S5b and S17 In particular, the solvent DMF used in the synthesis process, as well as the Pd/C catalyst in the synthesis of diamine monomer, can be recycled and reused in industrial production. 36,37 Characterization Methods. The 1 H NMR and 13 C NMR spectra of the newly synthesized daidzein-based dianhydride and diamine monomers were recorded on a Bruker AVANCE III HD 500.…”

Redox Electrochemistry of Mn(II) via Carbon Black Nanoparticle Impacts

“…Impacts were observed with an onset potential of −1.45 ± 0.01 V (vs SCE), in good agreement with Figure 1, and a plot of the charge passed (Q/fC) is given in Figure 3 along with a typical chronoamperogram. It is noted that a variety of spike forms are present from single sharp features to larger "step on, step off"-type signals, indicating a range of impact durations and particle−electrode interactions 33,61 as shown in Figure 3A.…”

“…Manganese is a commercially significant metal used in applications such as batteries and steelmaking. , If manganese is left untreated in wastewater, it can cause detrimental health effects, in severe cases leading to “manganism” affecting the central nervous system. , Current recovery methods of manganese from battery waste rely on metallurgical techniques , following an initial physical separation step: a technique such as nanoimpact electrochemistry may be advantageous in terms of efficiency, as it can simplify the recovery process . The bulk electrodeposition of Mn has been well-studied in the literature, primarily in sulfate and chloride solutions. − Despite the higher current efficiency observed when using chloride baths, it is conventionally produced from manganese­(II) sulfate/ammonium sulfate solutions to avoid the formation of Cl 2 gas and due to the corrosive nature of the solution .…”

“…Here, we assume that during impacts, the metal is reduced onto the particle itself; however, when the working electrode and particles are the same material (e.g., carbon), competition can occur between these two materials, and there is a possibility of metal ions being reduced/oxidized on the electrode surface during “impact”. Analysis of the resulting transient signals can determine a range of information including nanoparticle size, concentration, and charge transfer kinetics of a system. − In the context of metal recovery, there are few reports concerning the electrodeposition of metals using nanoimpact electrochemistry, and until recently, these were limited to metal nanoparticle cores only. − More recently, the electrodeposition of copper onto fly-ash cenospheres and palladium on carbon black has been reported as well as the rapid screening of bimetallic catalysts. ,, …”