fig5
![Recent advances in earth-abundant first-row transition metal (Fe, Co and Ni)-based electrocatalysts for the oxygen evolution reaction](https://image.oaes.cc/92b7fbf7-13f1-4589-b2f9-a2999bf9db55/5063.fig.5.jpg)
Figure 5. (A) Molecular structure of Co3-xCrxO4 electrocatalysts and energy density comparison by changing the (1) Cr content and (2) representative RDEVs of Co3O4 (black), Co2.75Cr0.25O4 (blue) and Co2.25Cr0.75O4 (green) in O2-sparged 1 M NaOH. Reproduced with permission. Copyright 2017, American Chemical Society[77]. (B) (1) Synthesis process and schematic structure of NiO/Co3O4@NC and (2) XPS spectra of Co 2p and Ni 2p. Reproduced with permission. Copyright 2017, American Chemical Society[78].