Electrooxidation of Alcohols on Mixed Copper–Cobalt Hydroxycarbonates in Alkaline Solution

Abstract

Mixed Cu‐Co hydroxycarbonates of the type (Cu1–xCox)2CO3(OH)2 have been synthesized over the whole range of Cu‐Co substitution (0≤x≤1) by co‐precipitation and their electrocatalytic activity in the oxidation reactions of ethanol (EOR), ethylene glycol (EGOR) and glycerol (GOR) in alkaline environment was evaluated to retrieve composition–activity correlations. Generally, cobalt incorporation led to higher activities for the alcohol oxidation (AOR) compared to the Cu‐only material and the results are compared with the competing oxygen evolution reaction (OER). On the Cu‐Co hydroxycarbonates, the electrooxidation of vicinal alcohols such as glycerol and ethylene glycol requires lower overpotentials than EOR and OER. Cu leaching from the hydroxycarbonate structure was observed in the presence of vicinal alcohols. The impact of chemical and electrochemical leaching of copper from the catalysts has been studied. The chemically leached catalyst was found to show increased AOR activity compared to other hydroxycarbonates, enabling the formation of larger amounts of formic acid during GOR measured in a circular flow cell electrolyzer. The results highlight that Cu‐Co hydroxycarbonates can be used as precursors to generate electrocatalytically active materials from Cu‐Co hydroxycarbonates for the AOR in alkaline solution.

Facile surface reconstructions of cobalt–copper phosphide heterostructures enable efficient electrocatalytic glycerol oxidation for energy-saving hydrogen evolution

“…JCPDS No. 48-0084), matching well with the literature reports on Co-Cu hydroxycarbonates 48,56. After annealing under a phosphine atmosphere, two new sets of XRD peaks appeared in the obtained sample.…”

“…12,45,46 In particular, metal oxides and hydroxides containing both Co and Cu have demonstrated good activity toward GOR. [47][48][49] Han et al 47 conducted an investigation using cobalt-based spinel oxide (MCo 2 O 4 ) as electrocatalysts for GOR, and discovered CuCo 2 O 4 was the best-performing catalyst with a high formate selectivity of ~80%. Braun et al 48 synthesized Cu-Co hydroxycarbonates (Cu 0.8 Co 0.2 ) 2 CO 3 (OH) 2 for alcohol oxidation reaction, and found Cu leaching could lead to increased catalytic activity.…”

“…12,45,46 In particular, metal oxides and hydroxides containing both Co and Cu have demonstrated good activity toward the GOR. [47][48][49] Han et al 47 conducted an investigation using cobalt-based spinel oxide (MCo 2 O 4 ) as an electrocatalyst for the GOR, and discovered that CuCo 2 O 4 was the bestperforming catalyst with a high formate selectivity of B80%.…”

“…Braun et al 48 synthesized Cu-Co hydroxycarbonates (Cu 0.8 Co 0.2 ) 2 -CO 3 (OH) 2 for alcohol oxidation reactions, and found that Cu leaching could lead to increased catalytic activity. Unfortunately, transition metal oxides and hydroxides are generally poor conductors, which may limit their electrocatalytic activity.…”

“…47–49 Han et al 47 conducted an investigation using cobalt-based spinel oxide (MCo 2 O 4 ) as an electrocatalyst for the GOR, and discovered that CuCo 2 O 4 was the best-performing catalyst with a high formate selectivity of ∼80%. Braun et al 48 synthesized Cu–Co hydroxycarbonates (Cu 0.8 Co 0.2 ) 2 CO 3 (OH) 2 for alcohol oxidation reactions, and found that Cu leaching could lead to increased catalytic activity. Unfortunately, transition metal oxides and hydroxides are generally poor conductors, which may limit their electrocatalytic activity.…”