Understanding Synergism of Cobalt Metal and Copper Oxide toward Highly Efficient Electrocatalytic Oxygen Evolution

Abstract

Understanding the synergism of bimetallic transition metal (TM)-based catalysts for oxygen evolution reaction (OER) is very difficult because it is complicated to identify the surface active sites in a bimetal system. Herein, we rationally designed Cu oxide (CuO x ) nanoarray film (NF) as an example to investigate the synergism and doping effects of iron group metals on OER. This is an advantage because CuO x is electrocatalytically inert and oxidatively stable, which is much better than carbon-based platforms. Especially, cobalt (Co) shows a much stronger synergism as compared with nickel (Ni) and iron (Fe). By introducing Co into the inert CuO x NFs, the Co active sites can be correlated to the OER activity by rationally regulating the morphology of CuO x NFs. In addition, the phase transformation from Cu2O to CuO occurs during the OER testing, further boosting the OER activity of Co-doped CuO x NF due to the hybridization change of Co active site. As a result, the Co-doped CuO x NF with 0.30 at. % Co (denoted as Co0.30CuO x ) shows a remarkable OER activity (an overpotential of 0.29 V at 10 mA cm–2) in basic solution, superior to those of the state-of-the-art OER catalysts. Both experimental and computational studies indicate that the introduction of Co-dopant in CuO x changes the rate-limiting step from M-OHads → M-Oads to M-Oads → M-OOHads and decreases the theoretical onset potential by 0.31 V. The optimal concentration of Co-dopant in CuO x nanocrystals renders the favorable surface properties for the electron transfer, the adsorption, and desorption of OER-relevant intermediates. Moreover, the small size of CuO x nanocrystals contributes to the large electrochemically active surface area, which enables the sufficient Co active sites to the electrolyte.

Biomass‐Templated Preparation of Hierarchically Multi‐Functional Ni/NiO@C Hollow‐Fibers

“…[26] The synergic effect reaches the best when the ratio of Ni to NiO is ≈2.84:1) (seen in Figure 4), which seems to be well-understood because reduction and oxidation always inter-exist. [28] Similarly, their ECSA and EIS are also carried (seen in Figure 8e,f) and their results support good electrocatalytic OER and HER performance of sample SM-1.25.…”

“…[ 26 ] The synergic effect reaches the best when the ratio of Ni to NiO is ≈2.84:1) (seen in Figure 4), which seems to be well‐understood because reduction and oxidation always inter‐exist. [ 28 ]…”

“d‐Electron Complementation” Induced V‐Co Phosphide for Efficient Overall Water Splitting

“…As the electron structure of Co ion in CoOOH is generally in the low‐spin state ( t 2g 6 e g 0 ), [ 60 ] the dominant interaction in the Co‐O‐Co unit is electron–electron repulsion between the fully occupied π‐symmetry ( t 2g ) d‐orbitals of Co 3+ and the bridging O 2− , which is unfavorable for the electron transfer from the oxygen‐containing ligand to the Co 3+ center. [ 61 ] As for V ions, the t 2g orbitals are empty or filled with unpaired electrons, which is in favor of the π‐donation from O 2p to V 3d. Thus, the repulsion between O 2p and Co 3d will be relieved, leading to a 3d electron compensation from Co to V in the V‐O‐Co unit.…”

Facile thermal exfoliation of Cu sheets towards the CuO/Cu2O heterojunction: a cost-effective photocatalyst with visible-light response for promising sustainable applications

“…16,17 Nowadays, large numbers of researchers are aiming to develop Cu-based composites and have harvested many achievements in this regard. [18][19][20] Although these studies are very innovative, there is still a lot of room for improvement. Actually, the synthesis processes of most heterogeneous photocatalysts belong to the liquid-phase reaction.…”