Co₃O₄–NiCo₂O₄ Hybrid Nanoparticles Anchored on N-Doped Reduced Graphene Oxide Nanosheets as an Efficient Catalyst for Zn–Air Batteries

Abstract

Developing efficient bifunctional electrocatalysts with excellent oxygen reduction and evolution reaction (ORR/ OER) activity to meet practical demands in Zn−air batteries (ZABs) is highly crucial and challenging. Herein, a simple hydrothermal one-step method is exploited to successfully synthesize Co 3 O 4 −NiCo 2 O 4 anchored on N-doped reduced graphene oxide nanosheets (Co 3 O 4 −NiCo 2 O 4 /N-RGO). The active sites present in Co 3 O 4 −NiCo 2 O 4 /N-RGO and the synergy between N-RGO and Co 3 O 4 −NiCo 2 O 4 accelerate the charge transfer and transport rate during the electrochemical course, which improves the ORR/OER activities of the Co 3 O 4 −NiCo 2 O 4 / N-RGO electrocatalyst. As expected, the Co 3 O 4 −NiCo 2 O 4 /N-RGO exhibits a better half-wave potential in the ORR and a lower Tafel slope during the OER process. A ZAB with optimal Co 3 O 4 −NiCo 2 O 4 /N-RGO as the cathode gives a higher open-circuit voltage (1.49 V), larger power density (97 mW cm −2 ), and better stability (180 h).

Hyper-Crosslinked Polymer-Derived Nitrogen-Doped Hierarchical Porous Carbon as Metal-Free Electrocatalysts for High-Efficiency Oxygen Reduction

“…Py-NHCP-1000 displays a stable potential platform of 1.49 V, and it is close to Pt/C (1.50 V). In addition, the peak power density of Py-NHCP-1000 is up to 165 mW cm –2 according to the polarization plots revealed in Figure c, which considerably precedes that of the Pt/C catalyst (127 mW cm –2 ) as well as those of most of the non-noble metal catalysts reported recently, − signifying its possible application potential for energy conversion. From the galvanostatic discharge curves shown in Figure d, an ignorable voltage drop is observed after 36 h, which reveals a high stability of ZAB with the Py-NHCP-1000 catalyst.…”

Live microalgal cells modified by L‐cys/Au@carbon dots/bilirubin oxidase layers for enhanced oxygen reduction in a membrane‐less biofuel cell

“…ACB@algae showed the highest reduction current density of 655.2 µA/cm 2 , which was 1.3 and 2.39 times of the ACB with O 2 bubbling and the ACB in microalgal suspension, respectively (Figure 5D). To better understand the advantages of in situ O 2 supply, the Tafel slope of ACB@algae was calculated to be 79.7 mV/dec, which was significantly smaller than those of the control groups (Figure 5E), indicating that the ACB@algae cathode has the fastest ORR kinetics 51,52 . This is because ACB@algae cathode not only enables the fast electron transfer, but also can make O 2 directly contact the BOD catalysts, without diffusing through the electrolyte.…”

“…To better understand the advantages of in situ O 2 supply, the Tafel slope of ACB@algae was calculated to be 79.7 mV/ dec, which was significantly smaller than those of the control groups (Figure 5E), indicating that the AC-B@algae cathode has the fastest ORR kinetics. 51,52 This is because ACB@algae cathode not only enables the fast electron transfer, but also can make O 2 directly contact the BOD catalysts, without diffusing through the electrolyte. The novel electrode constructed by the hybrid of functional material-live microalgal cells can enhance ORR kinetics, and save the cost of pure O 2 supply as well as the mechanical aeration.…”

Carbon Nanofibers as Potential Catalyst Support for Fuel Cell Cathodes: A Review

“…Considerable research has been undertaken in the past decade to discover alternative, cost-effective ORR catalysts made up of transition metals such as Fe, Co, Ni, and Mn, especially in combination with the N-doped carbons, which generate potentially ORR active sites, namely M-N-C. − S. G. Peera et al synthesized a durable GNF catalyst by the deposition of Fe and Co species on the N-F/GNF catalysts (Fe-Co/NF-GNF). The GNFs transformed to graphene structures and the metallic nanoparticles were encapsulated by the N-F graphene layers.…”