Tuning nitrogen species in 3D porous carbon via boron doping for boosted Zn-ion storage capability

Abstract

Edge located nitrogen (edge-N) species in carbon materials have been commonly recognized as one of the most active sites for Zn²⁺ storage, by virtue of their more accessible microstructure and lower adsorption energy barrier. However, modulating N species types and enriching the concentration of edge-N (pyridinic-N and pyrrolic-N) are still daunting challenges. In this work, the conversion of graphitic-N to edge-N in a carbon matrix was creatively realized by the additional incorporation of boron element and the ratio of edge-N reached up to 81.6% in terms of the total N content. The optimized B-doped rich edge-N porous carbon (BENC) with matchable pore size to accommodate solvated Zn²⁺ and abundant zincophilic sites exhibits outstanding Zn²⁺ storage capabilities and delivers a high reversible capacity (354.6 F g⁻¹ at 0.1 A g⁻¹), excellent power density (126.2 W h kg⁻¹) and almost no capacity loss after 20 000 cycles. Moreover, density functional theory (DFT) calculations further discover that B/edge-N sites reduce the adsorption energy barrier of Zn²⁺, contributing to the invertible adsorption/desorption of Zn²⁺. This study demonstrates the synergistic effect of B and N dopants on capacity enhancement in carbon materials for Zn²⁺ storage applications.