Abstract
Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical half-reactions in energy conversion devices such as metal-air batteries and reversible fuel cells, and their sluggish kinetics severely limit the overall device performance. Therefore, the development of efficient, stable, and low-cost non-precious metal bifunctional electrocatalysts is of great significance. In this study, a MOF-derived bifunctional electrocatalytic material (NiFe@CNT), featuring NiFe bimetallic alloys uniformly anchored within a carbon nanotube network, was successfully fabricated using a two-dimensional metalloporphyrin-based Fe-MOF precursor via metal site modulation by introducing Ni, combined with a high-temperature pyrolysis strategy. Structural characterization results indicate that NiFe@CNT possesses an intact three-dimensional CNT conductive network, a high degree of graphitization (I (D)/I (G) = 0.39), and uniformly dispersed NiFe alloy active phases. Electrochemical evaluations reveal that NiFe@CNT functions as a highly active bifunctional catalyst for both ORR and OER in alkaline environments. Regarding its ORR activity, the material exhibits a half-wave potential comparable to that of benchmark Pt/C, with reaction kinetics proceeding through an approximately four-electron transfer mechanism. In terms of OER performance, a current density of 10 mA cm(-2) is attained at a modest overpotential of merely 1.514 V. In alkaline electrolyte, the ORR proceeds predominantly through a four-electron pathway converting O(2) to H(2)O (O(2) + 4H(+) + 4e(-) → 2H(2)O), while the OER involves the reverse four-electron oxidation of hydroxide to produce molecular oxygen (2H(2)O → O(2) + 4H(+) + 4e(-)). Furthermore, durability assessments confirm that NiFe@CNT surpasses commercial noble metal benchmarks in long-term operational stability. This work presents a viable approach for fabricating advanced noble-metal-free oxygen electrocatalysts through two-dimensional MOF-derived engineering.