Auspicious Metal-Doped-Cu₂O/Cu Dendrite (M=Ni, Co, Fe) Catalysts for Direct Alkaline Fuel Cells: Effect of Dopants

Abstract

Herein, honeycomb nickel-, cobalt-and iron-doped Cu 2 O/Cu foams with dendrite-like structures are in-situ formed atop of a copper foil substrate using the facile and low-cost dynamic hydrogen bubbles template technique (DHBT), wherein the copper nanoparticles are electrodeposited and grow in the interstitial spaces between the hydrogen bubbles. The incorporation of nickel, cobalt and iron impurities (less than 4%) into the Cu 2 O/Cu structures improved their performance significantly for various electrochemical reactions including water splitting, glucose and glycerol electrooxidation. This outstanding enhancement is attributed to the catalysts dendritic structures providing an easily accessible high active surface area. In addition, the doped metals are believed to increase the electrochemically active surface area and to facilitate the electron transfer in the studied reactions. Besides, the presence of these dopants improved the adsorption of glucose and glycerol molecules on the copper surface active sites together with increasing the Cu 2 O's inherent conductivity.

Tailor‐Designed Porous Catalysts: Nickel‐Doped Cu/Cu2O Foams for Efficient Glycerol Electro‐Oxidation

“…proposed the redox transformation between Cu oxides/hydroxides, e. g., Cu/Cu + , Cu + /Cu 2+ , and Cu 2+ /Cu 3+ in the potential region from 0 to 0.06 V vs. SCE where GOR takes place effectively. Thus, the surface of the porous Cu/Cu 2 O is oxidized to CuO and subsequently to higher oxidation states, e. g., CuOOH which acts as a catalytic mediator (with high oxidizing power) facilitating the electrochemical oxidation of glycerol . A similar assumption has been proposed by Di Tocco et al…”

“…Thus, the surface of the porous Cu/Cu 2 O is oxidized to CuO and subsequently to higher oxidation states, e. g., CuOOH which acts as a catalytic mediator (with high oxidizing power) facilitating the electrochemical oxidation of glycerol. [51] A similar assumption has been proposed by Di Tocco et al [12] The performance of the as-prepared Cu/Cu 2 O foams has been compared to recent publications employing Cu-based and commercial Pt catalysts, see Table S1. As seen in this table, our proposed Cu/Cu 2 O foams showed comparable or even better electrocatalytic activity towards GOR compared to many of the published electrocatalysts.…”

“…The origin of the electrocatalytic activity of the proposed Cu/Cu 2 O porous foam catalysts might originate from a mediated catalytic role of the Cu ions in several oxidation states . For instance, El‐Nagar et al . proposed the redox transformation between Cu oxides/hydroxides, e. g., Cu/Cu + , Cu + /Cu 2+ , and Cu 2+ /Cu 3+ in the potential region from 0 to 0.06 V vs. SCE where GOR takes place effectively.…”

“…The origin of the electrocatalytic activity of the proposed Cu/Cu 2 O porous foam catalysts might originate from a mediated catalytic role of the Cu ions in several oxidation states. [48][49][50] For instance, El-Nagar et al [51] proposed the redox transformation between Cu oxides/hydroxides, e. g., Cu/Cu + , Cu + /Cu 2 + , and Cu 2 + /Cu 3 + in the potential region from 0 to 0.06 V vs. SCE where GOR takes place effectively. Thus, the surface of the porous Cu/Cu 2 O is oxidized to CuO and subsequently to higher oxidation states, e. g., CuOOH which acts as a catalytic mediator (with high oxidizing power) facilitating the electrochemical oxidation of glycerol.…”

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

“…[34][35][36][37] Moreover, the combination of both Cu and Co in bimetallic systems has been shown to be electrocatalytically advantageous for the electrochemical glycerol oxidation reaction (GOR). [38][39][40] Zhu et al synthesized a CuCo-MOF/polyaniline composite, which revealed higher electrocatalytic activity for GOR than the corresponding monometallic Cu-/Co-MOF or the pure CuCo-MOF without polyaniline in 0.5 M KOH and 0.5 M glycerol. [38] El-Nagar et al prepared a catalyst series of metaldoped-Cu 2 O/Cu by using a dynamic hydrogen bubble template technique, tested for GOR in 2 mM glycerol and 0.1 M KOH solution.…”