l-Lysine-induced green synthesis of CoS/Co₃O₄ nanoframes for efficient electrocatalytic oxygen evolution

Abstract

The Co-based heterojunction is regarded as one of the efficient materials for oxygen evolution reaction (OER), but the synthesis is still faced with time- and labor-consuming, and environmentally unfriendly. Herein,...

Co/Co3O4 Heterojunctions Encased in Porous N-Doped Carbon Nanocapsules for High-Performance Cathode of Rechargeable Zinc–Air Batteries

“…The two dominant binding energy peaks at 781.5 and 798.0 eV originate from the Co 3+ , and two dominant binding energy peaks at 784.2 and 800.5 eV can be attributed to the Co 2+ . − It is noteworthy that the Co 3+ and Co 2+ binding energy peaks of Co/Co 3 O 4 @NC have positively shifted by ∼0.8 eV compared with those of Co–Co 3 O 4 @NC, which indicates that the formation of Co/Co 3 O 4 heterojunction caused the change in the electronic structure of Co 3 O 4 . It has been shown that due to the difference in charge density in the Co/Co 3 O 4 heterostructure, the strong electron absorption ability of the O atom in Co 3 O 4 leads to the spontaneous charge flow of the adjacent zerovalent metal Co atom to Co 3 O 4 . , In addition, according to the area ratio of the fitting peak at XPS Co 2p, it can be roughly estimated that the ratio of Co to Co 3 O 4 in Co/Co 3 O 4 @NC was about 3:10. The XPS C 1s of Co/Co 3 O 4 @NC is also deconvolved into three major peaks, including the C–C bond, C–N/C–O bond, and CO bond. , The presence of a C–N bond also indicates that N has entered the lattice of carbon (Figure S6).…”

“…The active site of the catalyst with Co/Co 3 O 4 heterojunction has been proved by the previous study, and the electrons will spontaneously transfer from the Co side to the Co 3 O 4 side across the Co/Co 3 O 4 interface upon direct contact, until the Fermi levels on both sides reach equilibrium. 23,26 Therefore, the catalytic active sites for OER and ORR tend to be on the Co site at the Co/Co 3 O 4 heterojunction interface. 22,25 Based on the above results, Co/ Co 3 O 4 @NC as a bifunctional catalyst does show many advantages in alkaline media.…”

“…23 To date, many heterogeneous catalysts have been obtained for OER and ORR, such as MnCo 2 O 4 / CeO 2 heterojunction catalyst, 24 CoO/CoS heterojunction catalyst, 25 and CoS/Co 3 O 4 heterojunction catalyst. 26 The heterojunction between the transition metal and Co 3 O 4 with different Fermi levels also can be constructed on the nanoscale, thus forming a Mott−Schottky heterostructure to generate a stable internal electric field and effectively enhance charge transfer. 27,28 Therefore, the construction of ORR/OER bifunctional catalysts with transition metal and Co 3 O 4 heterojunctions can greatly optimize the chemisorption energy of oxygen intermediates and significantly improve charge transport, which will be a promising strategy to achieve highly efficient ORR/OER bifunctional catalysts.…”

“…To solve this problem, the ORR and OER electrocatalytic properties of Co 3 O 4 were improved through interface engineering, local electronic regulation, porous carbon hybridization, and other strategies. , Especially in terms of local electron regulation, the establishment of a heterojunction interface structure between two phases can induce electron reconfiguration and change the local electron state, accordingly accelerating charge transfer and significantly enhancing the catalytic performance . To date, many heterogeneous catalysts have been obtained for OER and ORR, such as MnCo 2 O 4 /CeO 2 heterojunction catalyst, CoO/CoS heterojunction catalyst, and CoS/Co 3 O 4 heterojunction catalyst . The heterojunction between the transition metal and Co 3 O 4 with different Fermi levels also can be constructed on the nanoscale, thus forming a Mott–Schottky heterostructure to generate a stable internal electric field and effectively enhance charge transfer. , Therefore, the construction of ORR/OER bifunctional catalysts with transition metal and Co 3 O 4 heterojunctions can greatly optimize the chemisorption energy of oxygen intermediates and significantly improve charge transport, which will be a promising strategy to achieve highly efficient ORR/OER bifunctional catalysts. , …”

Deep sulfur doping induces the rapid electrochemical self-reconstruction of Ni–Fe hydroxide to drive water oxidation

“…The oxygen evolution reaction (OER) plays a fundamental and important role in clean energy conversion devices, 1 such as water splitting [2][3][4] and metal-air batteries. 5,6 However, the conversion efficiency of these devices heavily suffers from the sluggish reaction kinetics and complex reaction pathways of the OER.…”