Plasma-Assisted Defect Engineering on p-n Heterojunction for High-Efficiency Electrochemical Ammonia Synthesis

Abstract

A defect-rich 2D p-n heterojunction, CoxNi3-x(HITP)2/BNSs-P (HITP: 2,3,6,7,10,11-hexaiminotriphenylene), is constructed using a semiconductive metal–organic framework (MOF) and boron nanosheets (BNSs) by in situ solution plasma modification. The heterojunction is an effective catalyst for the electrocatalytic nitrogen reduction reaction (eNRR) under ambient conditions. Interface engineering and plasma-assisted defects on the p-n CoxNi3-x(HITP)2/BNSs-P heterojunction led to the formation of both Co-N3 and B…O dual-active sites. As a result, CoxNi3-x(HITP)2/BNSs-P has a high NH3 yield of 128.26 ± 2.27 µg h−1 mgcat.−1 and a Faradaic efficiency of 52.92 ± 1.83% in 0.1 m HCl solution. The catalytic mechanism for the eNRR is also studied by in situ FTIR spectra and DFT calculations. A CoxNi3-x(HITP)2/BNSs-P-based Zn-N2 battery achieved an unprecedented power output with a peak power density of 5.40 mW cm−2 and an energy density of 240 mA h gzn−1 in 0.1 m HCl. This study establishes an efficient strategy for the rational design, using defect and interfacial engineering, of advanced eNRR catalysts for ammonia synthesis under ambient conditions.