Polyaniline layered N-doped carbon-coated iron oxide nanocapsules for extremely active Li-ion battery anode and oxygen evolution reaction.

We report the effective synthesis of polyaniline (PANi)-layered nitrogen-doped carbon-coated Fe 3 O 4 (FNC@PANi) nanocapsules (NCs) for electrocatalysis of oxygen evolution reaction (OER) as well as anode material for lithium (Li)-ion batteries (LIBs) via a simple hydrothermal method and oxidative polymerization technique. The prepared FNC@PANi NCs revealed a dual core-shell structure, in which an intermediate carbon layer allowed excellent electrical conduction between the Fe 3 O 4 NCs and PANi. The dual core-shell structure also allowed the Fe 3 O 4 NCs to expand freely during the Li-ion insertion/extraction and OER processes without breaking the outer layer, thus providing a high surface area (147.85 m2 g−1) and enhanced electrical conductivity. These properties facilitate the application of the dual core-shell FNC@PANi NCs as an advanced electrode material for LIBs, delivering a high reversible specific capacity of 1556.48 mAh g−1 at 0.1 A g−1, excellent rate performance (896.96 mAh g−1 at 1 A g−1), and durable cycling life (680.12 mAh g−1 at 5 A g−1 for 3000 cycles). The dual core-shell FNC@PANi NCs exhibited high electrocatalytic activity in the OER, with a small Tafel slope of 108.7 mV dec−1 owing to synergistic effects between the copious active sites of the Fe 3 O 4 NCs and the carbon core-shell structure and a modest overpotential of 219 mV at 10 mA cm−2. The electrodes showed excellent stability over 10 h, as determined by chronopotentiometry at 10 mA cm−1. The resultant dual-core-shell FNC@PANi NCs are efficient iron-oxide-based electrode materials for LIBs and OER electrocatalysts. Facile solvothermal method and chemical oxidative polymerization technique are reported for the synthesis of bifunctional electrocatalyst and high-performance LIB anode material, i.e., dual core-shell polyaniline layered nitrogen-doped carbon coated Fe 2 O 3 nanocapsules (dual core-shell FNC@PANi NCs). Compared to its counterparts, this FNC@PANi NCs electrode delivers excellent energy storage properties along with higher OER behavior. [Display omitted] • A bifunctional electrode material for lithium-ion battery (LIB) and oxygen evolution reaction (OER) electrocatalyst, namely dual core-shell FNC@PANi NCs, was synthesized via a hydrothermal method. • The material serves as an advanced LIBs electrode, exhibiting impressive cycling stability, excellent rate capability, and durable cycling life. • As an OER electrocatalyst, the FNC@PANi NCs demonstrate significant catalytic activity, evidenced by small Tafel slope and modest overpotential. [ABSTRACT FROM AUTHOR]