Heteroatom-doped Carbon Materials Derived From Biomass For The Oxygen Reduction Reaction

The oxygen reduction reaction?ORR? is important in many fields,such as energy conversion,corrosion,and biology.For fuel cells,cathodic oxygen reduction is an essential limiting factor on their performance.To construct fuel cells with superior performance,efficient efforts have been done to promote the ORR.Traditionally,platinum and its alloy have been regarded as the best catalysts for ORR,but they still suffer from multiple drawbacks,including their instability to time-dependent drift,CO poisoning effects and Me OH crossover.Meanwhile,the high cost and limited resources of Pt have also made the Pt and Pt-based catalysts the primary barrier to large-scale application of fuel cells.Thus,more efforts are needed to find alternative catalysts that not only are efficient,low-cost,durable,but also show comparable/better catalytic performance to/than Pt.Carbon nanomaterials?CNMs? have received greater attentions,owing to their interesting catalytic,optical and electrical properties.As the electronegativity and size of the heteroatoms are different from those of carbon,the introduction of heteroatoms?e.g.,nitrogen,phosphorus,sulfur?into CNMs could cause electron modulation to change the electronic properties and the ORR activity.Thus,a variety of heteroatoms-doped CNMs have been synthesized from melamine,thiourea,dicyandiamide et al.The toxic raw materials and complex synthesis procedure seriously limit the large-scale production.It is highly expected to develop cost-effective heteroatom-doped CNMs with excellent ORR electrocatalytic activity by using simpler procedures and more environmentally friendly precursors.As a result,we prepared heteroatom-doped CNMs with the cheap,naturally abundant biomass as precursor for ORR,and carried out the following works:?1?Study on the preparation and ORR performance of biomass-based N-doped porous carbon material.The as-prepared sample with high Brunauer-Emmett-Teller surface area(851.41 m² g^-1)possessed excellent ORR performance.Its onset potential was just negative?about 10 m V?than that of Pt/C,and more interestingly,the current density was almost double that of Pt/C.Besides,the tolerance to methanol and stability of the as-prepared sample were also superior to those of Pt/C.The excellent performance was probably due to the balance of superhydrophilicity,rich active sites,superior electrical conductivity,and3D structure,.?2?Study on the preparation and ORR performance of the self-constructed N-,S-and P-tridoped porous carbon material from cassia leaf.Here,we demonstrated a large-scale,one-pot protocol for the preparation of a new N-,S-and P-tridoped porous carbon by using resource-rich Cassia leaf,a kind of biowaste,as precursor.The sample carbonized at 800 ^o C?named CL-800?showed the superior performance,i.e.,the onset potential was just 33 m V negative than that of commercial Pt/C,most importantly,the current density(for CL-800 is 1.50 m A cm^-2)was double that of Pt/C(0.69 m A cm^-2).Beyond that,CL-800 had better durability and smaller crossover effect than those of Pt/C.?3?Study on the the preparation and ORR performance of N-,S-codoped porous carbon material from ginger.Although the onset potential of our sample is slightly negative than that of Pt/C,the other parameters?e.g,current density,tolerance against methanol and CO,durability?judging the performance of a catalyst were better than those of Pt/C.Our experimental results further prove that the biomass-derived CNMs are the potential ORR catalysts.