Co modified N, P, B tri-doped porous yolk-shell biochar microspheres as catalyst for oxygen evolution reaction

Abstract

Designing low-cost and high-activity electrocatalysts is crucial for improving the slow kinetic process of the oxygen evolution reaction (OER) and meeting global energy demands. This study focuses on the preparation of a novel OER catalyst, labelled Co@NPBC, which exhibits a porous yolk-shell configuration. The structure of Co@NPBC consists of N, P, B-doped carbon microspheres, amalgamated with the transition metal Co, and it is fabricated via a simple impregnation–carbonisation method. The doping of heteroatoms has the potential to modify both the charge and spin density of carbon atoms, while the presence of Co enhances the electrical conductivity of the material, which accelerates the electron transmission process. The porous structure provided numerous active sites for the reaction to occur, specifically at the catalytic interface. Furthermore, the yolk-shell structure serves a supportive function, ensuring the stability of the overall catalyst architecture. Upon testing in an alkaline environment, the Co@NPBC material demonstrated exceptional OER catalytic activity (η10: 355 mV, Tafel slope: 71.4 mV·dec−1). The results showed that the synergistic effect of carbon microspheres doped with heteroatoms and Co nanoparticles increased the OER catalytic activity and subsequently enhanced water splitting efficiency. For a comparative analysis, catalysts with either single (Co@NC, Co@BC, and Co@PC) or double doping (Co@NPC, Co@NBC, and Co@BPC) were also prepared. The results showed that Co@NPBC exhibited better OER catalytic activity than the other catalysts.