Karajagi Imran, Ramya K, Ghosh P C, Sarkar A, Rajalakshmi N
Centre for Fuel Cell Technology (CFCT), International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) 2nd Floor, IIT-M Research Park, Block E, 6 Kanagam Road, Taramani Chennai - 600113 India
Centre for Research in Nanotechnology and Science (CRNTS), Indian Institute of Technology Bombay Powai Mumbai - 400076 India.
RSC Adv. 2020 Sep 30;10(59):35966-35978. doi: 10.1039/d0ra07100e. eCollection 2020 Sep 28.
The design of stable and high performance metal free bifunctional electrocatalysts is a necessity in alkaline zinc-air batteries for oxygen reduction and evolution reaction. In the present work co-doped carbon materials have been developed from polymeric precursors with abundant active sites to achieve bifunctional activity. A 3-dimensional microporous nitrogen-carbon (NC) and co-doped nitrogen-sulfur-carbon (NSC) and nitrogen-phosphorus-carbon (NPC) were synthesized using poly(2,5-benzimidazole) as an N containing precursor. The obtained sheet like structure shows outstanding ORR and OER performance in alkaline systems with excellent stability compared to Pt/C catalyst. The doped heteroatom in the carbon is expected to have redistributed the charge around heteroatom dopants lowering the ORR potential and modifying the oxygen chemisorption mode thereby weakening the O-O bonding and improving the ORR activity and overall catalytic performance. The bifunctional activity (Δ = - ) of an air electrode for NPC, NSC, NC and Pt/C is 0.82 V, 0.87 V, 1.06 V and 1.03 V respectively, and the NPC value is smaller than most of the reported metal and non-metal based electrocatalysts. The ORR (from onset potential) and OER (10 mA cm) overpotential for NPC, NSC, and NC is (290 mV, 410 mV), (310 mV, 450 mV) and (340 mV, 600 mV) respectively. In the prepared catalyst the NPC exhibited higher ORR and OER activity (NPC > NSC > NC). The doping of P in NPC is found to have a great influence on the microstructure and therefore on the ORR and OER activity.
设计稳定且高性能的无金属双功能电催化剂对于碱性锌空气电池中的氧还原和析氧反应来说是必不可少的。在目前的工作中，已经从具有丰富活性位点的聚合物前驱体开发出了共掺杂碳材料，以实现双功能活性。使用聚（2,5-苯并咪唑）作为含氮前驱体合成了三维微孔氮碳（NC）以及共掺杂的氮硫碳（NSC）和氮磷碳（NPC）。与Pt/C催化剂相比，所获得的片状结构在碱性体系中表现出出色的氧还原反应（ORR）和析氧反应（OER）性能以及优异的稳定性。预计碳中掺杂的杂原子会使杂原子掺杂剂周围的电荷重新分布，降低ORR电位并改变氧的化学吸附模式，从而削弱O-O键并提高ORR活性和整体催化性能。NPC、NSC、NC和Pt/C空气电极的双功能活性（Δ = - ）分别为0.82 V、0.87 V、1.06 V和1.03 V，并且NPC的值小于大多数已报道的基于金属和非金属的电催化剂。NPC、NSC和NC的ORR（从起始电位）和OER（10 mA cm）过电位分别为（290 mV，410 mV）、（310 mV，450 mV）和（340 mV，600 mV）。在所制备的催化剂中，NPC表现出更高的ORR和OER活性（NPC > NSC > NC）。发现NPC中P的掺杂对微观结构有很大影响，因此对ORR和OER活性也有很大影响。
