Hollow-structured CoP nanotubes wrapped by N-doped carbon layer with interfacial charges polarization for efficiently boosting oxygen reduction/evolution reactions

Abstract

• 1D hollow CoP nanotubes wrapped by NCL are used as efficient catalysts for ORR/OER. • The well-formed 1D hollow structure can exposure more active sites for mass transfer. • CoP/CoOOH heterostructure on CoP-HNTs surface as the main active-species for OER. • Charge redistribution at the CoP/NCL interface promotes both ORR and OER processes. • Graphene layer protects CoP-HNTs@NCL from aggregation and corrosion during ORR/OER. Structure engineering for electrocatalysts via interfacial charge redistribution plays a vital role in governing the electrocatalytic activity for both oxygen reduction and evolution reactions (ORR/OER). Herein, a hierarchical nanostructure consisting of one-dimension (1D) hollow CoP nanotubes wrapped by nitrogen-doped carbon layer (CoP-HNTs@NCL) is designed through a simple hydrothermal-phosphorization-annealing strategy. Morphology of CoP-HNTs@NCL-0.4 (mass ratio of GO to CoP is 0.4) shows that the exterior surface of hollow CoP-HNTs is firmly coated by NCL with a layer thickness of 5-8 nm. ΔE (E j10 (1.58 V, OER)-E 1/2 (0.91 V, ORR)) of CoP-HNTs@NCL-0.4 is as low as 0.67 V for ORR/OER, which outperforms commercial Pt/C and RuO 2 and ranks the top of nonprecious-metal catalysts. Excellent activity and stability of CoP-HNTs@NCL-0.4 for ORR/OER benefit from synergistic effects between CoP and NCL, enhanced mass transfer via 1D hollow structure, and abundant active sites exposed on the interior/exterior surfaces of nanotube wall. Density functional theory calculations confirm that strong coupling interactions lead to interfacial charge polarization to remarkably promote the ORR/OER activities. This study highlights the functions of 1D hollow structure and interface effects in oxygen electrocatalysis, and opens a new avenue for interface construction by synergistically integrating favorable thermodynamics with efficient kinetics through modification of electronic structure.