Songliang Liu¹, Huaifang Teng¹, Kun Ma¹, Weixin Miao¹,Xiaotong Zhou¹, Xuejing Cui¹, Xin Zhou^2,3*, Luhua Jiang¹* and Bao Yu Xia⁴*

¹ Electrocatalysis & Nanomaterial Laboratory, College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, China

² Interdisciplinary Research Center for Biology and Chemistry, Liaoning Normal University, Dalian, Liaoning, 116029, China

³ College of Environment and Chemical Engineering, Dalian University, Dalian 116622, China

⁴ School of Chemistry and Chemical Engineering, State Key Laboratory of Materials Processing and Die & Mould Technology, Key Laboratory of Material Chemistry for Energy Conversion and Storage (Ministry of Education), Hubei Key Laboratory of Material Chemistry and Service Failure, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology (HUST), 1037 Luoyu Rd, Wuhan 430074, China

E-mail: zhouxin@dlu.edu.cn, luhuajiang@qust.edu.cn, byxia@hust.edu.cn

Abstract:

Unraveling the fundamental determinants of the intrinsic activity of practical catalysts has long been challenging, mainly due to the complexity in structures and surfaces of such catalysts. Current understandings of intrinsic activity mostly come from model catalysts. Here, a pH-induced ligand adsorption strategy is developed to achieve controllable synthesis of self-assembled low-dimensional PdMo nanostructures, including 1D nanowires, 2D metallenes, and 2D metallene nanoveins. We establish a strong correlation between the intrinsic oxygen reduction reaction (ORR) activity and the density of grain boundaries. Increased grain boundary density induces moreextensive tensile strain, which, in synergy with electronic interactions within PdMo alloys, effectively lowers the energy barrier of the rate-determining step (*O to *OH).2D PdMo metallene nanoveins, featuring the highest grain boundary density and a unique mesoporous structure, exhibit superior ORR activity and mass transport capabilities. Computational fluid dynamics simulations and in-situ spectroscopy are employed to elucidate the structure-activity relationship. This work provides fundamental insights into the critical role of grain boundary engineering in enhancing ORR electrocatalysis in Pd-based nanostructures.

Keywords: Low-dimensional materials;structure-activity relationship; metallenes; grain boundary; oxygen reduction.