Roy Dipayan, Panigrahi Karamjyoti, Das Bikram K, Ghorui Uday K, Bhattacharjee Souvik, Samanta Madhupriya, Sarkar Sourav, Chattopadhyay Kalyan K
School of Materials Science and Nanotechnology, Jadavpur University Kolkata-700032 India
Department of Physics, Jadavpur University Kolkata-700032 India.
Nanoscale Adv. 2021 Jun 14;3(16):4739-4749. doi: 10.1039/d1na00304f. eCollection 2021 Aug 10.
The incorporation of vacancies in a system is considered a proficient method of defect engineering in general catalytic modulation. Among two-dimensional materials, the deficiency of surface active sites and a high band gap restrict the catalytic activity of hexagonal boron nitride (hBN) material towards the oxygen reduction reaction (ORR), which hinders its applicability in fuel cells. A bane to boon strategy has been introduced here by coupling two sluggish ORR materials (hBN & MoS) by a probe-sonication method to form a heterostructure (termed HBPS) which fosters four electron pathways to assist the reduction of oxygen. Theoretical and experimental studies suggest the kinetically and thermodynamically favorable formation of boron vacancies (B-vacancies) in the presence of MoS, which act as active sites for oxygen adsorption in HBPS. B-vacancy induced uneven charge distribution together with band gap depression promote rapid electron transfer from the valance band to the conduction band which prevails over the kinetic limitation of pure hBN nanosheets towards ORR kinetics. The formed B-vacancy induced HBPS further exhibits a low Tafel slope (66 mV dec), and a high onset potential (0.80 V RHE) with an unaltered electrochemically active surface area (ESCA) after long-term cycling. Thus, vacancy engineering in hBN has proved to be an efficient approach to unlock the potential of catalytic performance enhancement.
在一般催化调制中，将空位引入系统被认为是一种有效的缺陷工程方法。在二维材料中，表面活性位点的缺乏和高带隙限制了六方氮化硼（hBN）材料对氧还原反应（ORR）的催化活性，这阻碍了其在燃料电池中的应用。本文引入了一种化害为利的策略，通过探针超声法将两种缓慢的ORR材料（hBN和MoS）耦合形成异质结构（称为HBPS），该异质结构促进了四条电子途径以协助氧的还原。理论和实验研究表明，在MoS存在下，动力学和热力学上有利于硼空位（B空位）的形成，这些硼空位在HBPS中作为氧吸附的活性位点。B空位引起的电荷分布不均匀以及带隙降低促进了电子从价带快速转移到导带，这克服了纯hBN纳米片对ORR动力学的动力学限制。形成的B空位诱导的HBPS进一步表现出低塔菲尔斜率（66 mV dec）和高起始电位（0.80 V RHE），并且在长期循环后电化学活性表面积（ESCA）不变。因此，hBN中的空位工程已被证明是释放催化性能增强潜力的有效方法。
