ORR and OER of Co–N codoped carbon-based electrocatalysts enhanced by boundary layer oxygen molecules transfer.

Two-step carbonization method was reported to synthesize Co–N doped coal tar pitch (CTP) carbon-based electrocatalysts with hierarchical pore structure, high local order degree and efficient Co-N x active structure simultaneously. The synergistic effect of the carbon substrate with highly ordered structure and the Co-N x active sites realized the "Point discharge effect". The π-π interactions from the CTP aromatic ring sheets and Co-N x promoted the adsorption and dissociation of oxygen molecules, respectively. The increased diffusion coefficient (D 0) indicated the mass transfer of oxygen molecules in the boundary layer was enhanced during the ORR process. Thanks to excellent structural characteristics, ACTP 5 @Co,N-800 exhibited better ORR performance than commercial Pt/C catalyst under alkaline conditions, and the OER activity was improved simultaneously. This work demonstrated a simple and practical strategy for the development of advanced carbon-based electrocatalysts, and also provided novel insights from kinetics perspectives for improving electrocatalytic efficiency. Image 1 • Two-step carbonization solves the contradiction between doping and ordering. • Ordered carbon and the Co-Nx site synergistic realize the "point discharge effect". • Multiscale structures enhance boundary layer mass transfer and electron gain and loss. [ABSTRACT FROM AUTHOR]