Electrocatalysis of Anodic Oxygen Transfer Reactions: Oxidation of Cyanide at Electrodeposited Copper Oxide Electrodes in Alkaline Media

Abstract

Films of copper oxide (CuO) were readily deposited electrochemically on conductive surfaces from alkaline solutions containing copper (I, II) cyanide. The resulting CuO-film electrodes showed catalytic activity for the anodic oxidation Of CN-to CNO-in alkaline media. The half-wave potential was pH dependent, indicating the involvement of OH-in the reaction mechanism. Electrocatalysis was concluded to occur by oxygen transfer mediation facilitated by formation of Cu Hz sites in the CuO surface. The deposited films were only loosely adherent to the substrates and were susceptible to chemical dissolution in the presence of excessively high CN-concentrations (ca. >> 1 mM) over a long time period (ca. 30 min).

Electrocatalytic oxidation of cyanide on copper-doped cobalt oxide electrodes

“…This catalytic activity is in agreement with the reported promotion of cyanide decomposition by copper species when using other elimination methods [38,39]. Nevertheless, the electrodeposited copper oxide films showed variable low stability and adherence [11,24,31,32], hindering their practical application for electrochemical cyanide destruction.…”

“…with equation (7) as overall reaction of (9) and (11). In this sense, and because both (10) and (11) are competing reactions, the high activity of Co 3 O 4 electrodes for the OER in alkaline media The electrocatalytic effect of copper on CN − oxidation in alkaline media has been previously studied and different mechanisms have been reported depending on the conditions used (pH, cyanide and copper concentrations, cell design and operating conditions) [11,[23][24][25][26][27][28]31,32,62].…”

“…On the other hand, various reports studied the electrocatalytic activity of electrodeposited copper oxide films for CN − electro-oxidation [11,[23][24][25][26][27][28]31,32]. In this case, the catalytic effect was attributed to the formation of active copper(III) species in the oxide film (in the form of CuO(OH) and/or Cu 2 O 3 ), with the Cu(III)-Cu(II) redox couple as electron transfer mediator [11].…”

“…In addition, they are very attractive for multiple electrochemical processes and devices [6][7][8][9][10][11]. Despite such relevance, however, their utilization as electrodes and/or electrocatalysts in electrolytic treatments is greatly restricted by their low mechanical and electrochemical stability [6,[11][12][13].…”

“…4 Several electrodes including carbon materials [23][24][25][26], stainless steel [27], bare Pt and Ni [28,29], boron-doped diamond (BDD) [30], CuO [11], and Ti-supported metal and metal oxide systems (the so-called dimensionally stable anodes, DSA) like PbO 2 [30,31], Pt [28,32], RuO 2 -TiO 2 and TaO 2 -IrO 2 [33], SnO 2 -SbO x [34,35], Co 3 O 4 [36,37], etc. were previously studied for the direct and indirect electrochemical oxidation of cyanide.…”