Enhanced Water Oxidation Activity of the Cobalt(II,III) Oxide Electrocatalyst on an Earth‐Abundant‐Metal‐Interlayered Hybrid Porous Carbon Support

Abstract

Supports over which electrocatalysts are deposited play a crucial role in the oxygen evolution reaction (OER), because they influence the surface roughness, morphology, electronic structure, and conductivity of electrocatalysts. In this context, we designed a hybrid carbon support having an earth‐abundant metal as an interlayer between a Co3O4 electrocatalyst and a carbon support. The present approach resulted in an electrode that was three dimensional with high porosity, provided low resistance to parallel electron conduction pathways through the metallic interlayer, and modulated the electrocatalytic activity of Co3O4 by affecting its electronic structure. To rationalize the effect of the metal interlayer, a range of non‐noble earth‐abundant metals (e.g. Cu, Mo, Ti, Al) were explored, of which the Cu‐modified carbon support resulted in maximum specific activity (i.e. activity per electrochemical surface area) for the OER. Whereas both the electronegativity and conductivity of the metal interlayer were found to influence the OER activity, the dominant controlling factor in the explored systems was conductivity. The specific activity of the OER of electrodeposited Co3O4 was found to have a near‐linear relationship between the electrical conductivity and the electron‐donor metals (e.g. Ti, Al) and another near‐linear relationship having different intercepts with electron‐acceptor metals (e.g. Cu, Mo, W). The above understanding can be useful in increasing the OER activity of electrocatalysts through support–electrocatalyst interactions.

Electrochemical Cycling‐Induced Amorphization of Cobalt(II,III) Oxide for Stable High Surface Area Oxygen Evolution Electrocatalysts

“…Further, O1s spectra enable the differentiation of the extent of crystal O‐, hydroxylated O‐ and structural H 2 O in the electrochemically treated Co‐oxide electrocatalysts. Three principal O1s peaks has been observed i. e. (1) non‐hydrogenated O‐bonded to Co‐atoms at 530.9 eV (O1), (2) OH‐bonded to Co atoms at 532.4 eV (O2) and (3) O‐ of structural H 2 O at 535.9 eV (O4) (Figure ) which corresponds to peaks assigned in the literature . Both crystalline Co 3 O 4 and Ox/Red‐Co 3 O 4 shows a peak around (∼529.1 eV O3 in Figure ) which is known to be the signature of co‐adsorption of OH with OH−O on Co .…”

“…The electrodeposited Co is converted to crystalline Co 3 O 4 before subjecting it for electrochemically induced amorphization process. The synthesis process of crystalline Co 3 O 4 involves electrodeposition of Co under electrochemically reducing condition on carbon support followed by thermal annealing to crystalline oxide . The XRD peaks of the synthesized material clearly shows the formation of highly crystalline spinel‐ Co 3 O 4 (JCPDS‐43‐1003) (Figure ).…”

“…Synthesis of crystalline Co 3 O 4 on carbon support: Co 3 O 4 electrocatalysts were synthesized by potentiostatic electrodeposition method on carbon support (electrode area: 1 cm 2 ) as elaborated in our previous work . Co was electrodeposited using 0.05 M of CoCl 2 .6H 2 O solution in de‐ionized (DI) water at a potential of −0.9 V for 30 minutes which deposit an amount of 38.2 mg on the carbon support.…”

“…The excellent chemical and mechanical stability, tuneable porosity and surface chemistry, high specific surface area, and excellent diversity in structure makes these MOFs derived suitable for electrocatalysis . This demands further improvement of electrocatalytic properties which can be achieved in following ways: 1) enhancing surface roughness of electrode which can increase the number of electrocatalytically active sites with formation of edges, steps and exposure of high‐Miller indexed surfaces, 2) use of highly porous three dimensional electrode, however, during assembling the electrode into device, the imposed clamping pressure has to be optimized so that porosity of three dimensional (3D) electrocatalyst is not significantly decreased while increasing contact with the current collector, (3) enhancing the conductivity of either electrocatalyst or support thereby reducing overall charge transport through electrode, (4) enhancing surface electrocatalytic activity either through doping or (5) support‐electrocatalyst interaction, (6) the specific activity of OER can also be increased either by altering the crystal structure (through polymorphic engineering) or through microstructure modification by introducing crystal defects, dislocations and grain boundaries…”

Significant Enhancement of the Photoelectrochemical Activity of CuWO4 by using a Cobalt Phosphate Nanoscale Thin Film

“…One popular and effective technique is through the surface modification of semiconductors . Iron, cobalt, and nickel based electrocatalysts have attracted most attention for water oxidation processes due to their remarkable electrocatalytic properties …”