Rationally constructing CoO and CoSe2 hybrid with CNTs-graphene for impressively enhanced oxygen evolution and DFT calculations

Constructing CoO–CoSe heterostructures through partial selenization of CoO is proposed to ameliorate the electrocatalytic performance of Co-based compounds toward oxygen evolution reaction (OER). Moreover, with reduced graphene oxide as a platform to in-situ grow N-doped bamboo-like carbon nanotubes encapsulating part of CoO and CoSe nanoparticles, we fabricated a novel hybrid (denoted as CoO–CoSe@N-CNTs/rGO) via a combination of two-stage calcination and subsequent selenization treatment. As an OER electrocatalyst in 1.0 M KOH, CoO–CoSe@N-CNTs/rGO affords low overpotentials (250 mV@10 mA cm and 322 mV@100 mA cm), favorable kinetics (a Tafel slope of 68 mV dec), and excellent durability, outperforming commercial RuO and most Co-based electrocatalysts reported till date. Comprehensive experiment results uncover that the exceptional electrocatalytic performance mainly emanates from the synergistic effect between CoSe and CoO in heterostructure, N doping effect in CNT and rGO, and the confining effect of N-CNTs and rGO for CoO–CoSe, resulting in more active sites and enhance conductivity. More importantly, density functional theory calculations disclose that the concurrent N doping and desirable encapsulation of the CoO–CoSe nanoparticle in N-CNT can optimize the adsorption energies of OER intermediates and increase the electric conductivity, thereby expediting the OER. This work is helpful to foster understanding on the structure–performance correlations of electrocatalysts with multi-active sites and multi-components for diverse applications.