Biomass-derived Ta,N,S co-doped CNTs enriched carbon catalyst for efficient electrochemical oxygen reduction

This work introduces nanostructured carbon-based composite with enriched CNTs and microstructural defects from pomelo peel biomass precursors through successive chemical pretreatment, heteroatom N, S dual-doping and transition metal oxide loading (Ta2Oy) and its application for electrochemical oxygen reduction reaction (ORR) at room temperature. During the microwave pyrolysis process, volatile N, S-containing species from trithiocyanuric acid reactant were trapped and doped into carbonaceous biomass precursor to achieving the rich-defect porous nanotubes and abundant cavity structure. The effect of biomass pretreatment on the textural and structural properties of biochar and formed CNTs were systematically investigated. The impacts of single doping (N) using melamine and dual-doping (N, S) with trithiocyanuric acid on the structural and electrochemical characteristics of biochar were evaluated. An optimized PP-NS-600-Ta-900 electrocatalyst displayed remarkable ORR activity with a half-wave potential of 0.82 V (vs. RHE), a limiting current density of −5.75 mA cm−2 and an electron transfer number of 3.85. The results offer a useful archetypical template to design and construct reliable CNTs enriched biomass-derived biochar for possible electrochemical energy and storage application, illustrating its viability for utilization as ORR electrocatalyst in potential applications, like fuel cells and metal-air batteries.