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In this research, a simple and economical process based on hydrometallurgy is developed to directly recycle platinum group metals from spent automotive catalysts to synthesize carbon supported platinum-group metals catalysts. Spent automotive catalysts are firstly leached by HCl+H2O2 system, resulting in Pd chloro-complexes. The optimized leaching rates of Pd and Rh are 97.99 ± 2.64% and 87.70 ± 1.23%, respectively. Then Pd precursor is separated from the leaching solution by precipitation, which can remove most impurities. The Pd precursor or Pd chloro-complexes solution can be used to synthesize carbon supported catalysts directly via an ethylene glycol reduction method. The samples are characterized by SEM, TEM, XRD, EDS, and ICP-OES. 2–4 nm Pd/C are successfully synthesized using recycled Pd. The recycled Pd/C exhibits excellent long-term stability, with no activity loss in the homemade SO3 2c depolarized electrolyser after 150 h of 100 mA cm−2 electrolysis. The electrochemical tests indicate that the recycled Pd/C samples are not inferior to Pd/C prepared from (NH4)2PdCl4 reagent. [ABSTRACT FROM AUTHOR]

Electrochemical conversion of CO2 to fuels powered by renewable energy is an attractive technology for carbon emission reduction and renewable energy utilization elevation. Here, electrochemical reduction of CO2 to selectively produce CO using a homemade electrolyzer and Au nanocatalyst was investigated. Au nanoparticles were uniformly anchored on N-doped carbon to improve catalytic activity, and the C/N ratio and operating temperature were adjusted to elevate catalytic selectivity. The resulting Au catalyst exhibited a current efficiency for CO production higher than 90% in a wide full cell voltage range (1.8 ~ 3.0 V), a high mass activity of 900 A gAu -1, and a total current density of 200 mA cm-2 under 3.0 V cell voltage at room temperature. A scale-up 3 × 3 cm CO2 electrolyzer was constructed and tested at 1 A, the current efficiency for CO production reached 93% but decreased within a few hours due to the potassium carbonate precipitation phenomenon at the cathode. The important influence of an unideal ion transport pathway during electrolysis on CO2 electrolyzer performance was revealed, and its stability can be greatly improved by using deionized water instead of KOH solution. [ABSTRACT FROM AUTHOR]