0646 GMT February 25, 2020
Their technique involves the electrodeposition of copper and/or palladium metal onto a thin film polymer via coordination of the metal to a cyanide-based ligand complex, sci24h.com wrote.
Because carbon dioxide is a greenhouse gas, researchers are interested in ways to decrease the amount of CO2 in our atmosphere. One feasible solution is to capture CO2 and reduce it to energy-rich hydrocarbon compounds. However, this needs to be done using methods that do not involve burning more fossil fuels for energy.
One method is to reduce CO2 using electrocatalysis. This involves using a metal catalyst within an electrochemical cell. Copper has been shown to be a good catalyst for the electrochemical reduction of CO2. However, there are some problems with using copper foils and crystals including low surface area, low catalytic current densities, and deactivation due to surface buildup. Copper nanoparticles have proved more desirable for these reactions, but their formation typically involves using surfactants, which are difficult to remove and often results in contamination.
The researchers demonstrate a technique in which they can produce copper nanoparticles that are the same size and evenly dispersed on a thin film on an electrode. This precludes the needs for a surfactant and allows for smaller particles, which has better catalytic efficiency.
The thin film used is poly-[Fe(vbpy)3][PF6]2 which is then treated with TBAPF6/CH3CN such that cyanide ions replace one of the bipyridine groups. These two cyanide groups, once part of the iron complex, serve as ligands for Cu(II). Electrochemical reduction of Cu(II) produces an ultrafine film of Cu(0) nanoparticles on the polymer surface.
They tested the generalizability of their technique using palladium to make palladium nanoparticles and CuPd nanoalloys. In testing their catalysts, CuPd had the highest Faradaic efficiency for the reduction of CO2. Furthermore, studies showed that in this reaction both CO and CH4 were present.
This technique involving the formation of metal or metal alloy nanoparticles on a thin film using coordination chemistry is a good step in finding ways to reduce carbon dioxide and form high energy carbon products that is environmentally safe and does not involve the use of contaminants.