Effect of Chromium Doping on Electrochemical Water Oxidation Activity by Co_3–xCr_xO₄Spinel Catalysts

Abstract

We have synthesized a series of Co3–x Cr x O4 (0 < x < 2) catalysts via thermal decomposition and explored their activity for the oxygen evolution reaction (OER). By changing the Cr content, we were able to modify the overall OER activity. Among the compositions investigated, Co2.25Cr0.75O4 is the most active, which achieves 10 mA cm−2 current density per geometric area and a mass activity of 10.5 A/g at 0.35 V overpotential. We hypothesize that this enhanced OER activity is due to the increase of the adsorption energy of the intermediates (*O, *OH, and *OOH) resulting from the increased electrophilicity of Co2+ sites in the material after the introduction of the electron-deficient Cr. This systematic doping strategy enables the investigation of the correlation between the doping and OER activity and allows for the rational design of future catalysts with higher activity and efficiency.

Coffee‐Waste Templating of Metal Ion‐Substituted Cobalt Oxides for the Oxygen Evolution Reaction

“…The XRD pattern of CW‐templated Co 3 O 4 (Figure ) shows distinct reflections that are well indexed to the spinel structure of Co 3 O 4 with cobalt atoms located at both tetrahedral and octahedral sites. When divalent (Cu, Ni) or trivalent cations (Fe, Cr) were introduced into Co 3 O 4 , the M−Co 3 O 4 (M=Cu, Fe, Ni, Cr) maintained the spinel structure, which is identical to that of pure Co 3 O 4 . This indicates that cobalt atoms in the spinel structure were substituted by the incorporated metal atoms.…”

“…It is known that the lattice of Co 3 O 4 can host many other metallic cations by partial cobalt substitution. By incorporating additional transition metals into the Co 3 O 4 lattice, the OER activity of Co 3 O 4 could be significantly enhanced –. In the case of M x Co 3− x O 4 species (M=Ni, Zn, Fe, Cr, etc.…”

NiFeCo oxide as an efficient and sustainable catalyst for the oxygen evolution reaction

“…The incorporation of Fe into nickel oxide enhances catalytic activity by modifying the local electronic structure, conductivity, and electrochemically active catalytic sites . Modification of the electronic band structure of the host oxide or hydroxide lattice by doping it with a metal can thus promote intermediate reactions that enhance catalytic kinetics . Although a vast number of binary and ternary multielement catalysts have been reported, the catalysts still suffer from poor electrochemical stability, which limits their large‐scale applicability.…”

“…19,20,[26][27][28][29] Modification of the electronic band structure of the host oxide or hydroxide lattice by doping it with a metal can thus promote intermediate reactions that enhance catalytic kinetics. 30,31 Although a vast number of binary and ternary multielement catalysts have been reported, the catalysts still suffer from poor electrochemical stability, which limits their large-scale applicability. Therefore, the challenge is to use convenient synthetic processes to fabricate superior and stable electrodes in alkaline or acidic media, as they often induce structural phase transformations in electrodes.…”

Water Oxidation Electrocatalysis with a Cobalt‐Borate‐Based Hybrid System under Neutral Conditions

“…The former methodh as been employed successfully to prepare mixed-metal oxidesw ith enhancedc atalytic activities. For example, the studies performed on NiCo 2 O 4 , [12] Zn x Co 3Àx O 4 , [13] CoAl 2 O 4 , [14] Cu x Co y O 4 , [15] and Co 2.25 Cr 0.75 O 4 [16] led to the conclusion that incorporation of different3 dm etal ions to cobalt oxidesi sasimple and efficient way to enhance the OER activity in comparison to Co 3 O 4 .T he latter methods uggests the use of anionic groups other than the oxide group, for example, boride, [17] nitride, [18] phosphide, [19,20] cyanide, [21,22] and phosphate. [23] Of these, cobalt phosphates have been studied intensely owing to their diversity,f acile synthesis, and more specifically,t he crucial role of the phosphate group in the water oxidationa ctivity and robustness of Co-Pi catalysts.…”