“…The close interaction was showed by high-magnification TEM (Fig. 1i 33,[36][37][38] The peaks of 2θ values at 12.8°, 18.1°, 28.8°, 37.5°, 42.0°, 50.0°, 56.4°, 60.3°, 65.1°, 69.7°and 72.7°are indexed to the (110), (310), ( 211), (301), (411), (600), ( 521), (002), ( 541) and (312) plane of MnO 2 , respectively, which is in accordance with MnO 2 (JCPDS 44-141). This observation reveals that the structure of MnO 2 belongs to the tetragonal system, which is α-MnO 2 .…”