Metal-selenides are one of the next-generation anode materials for sodium-ion batteries (SIBs), but they suffer from sluggish charge/ion transport, huge volume expansion and aggregation of particles. Herein, ZnSe/C composites with Zn–O–C bonds and 3D hierarchical structure were successfully prepared. Precisely, ZnSe nanoparticles are tightly riveted in the 3D carbon matrix crosslinking by Zn–O–C bonds. The 3D carbon network improves structure stability by restricting volume expansion. More importantly, experimental results along with DFT calculations reveal that Zn–O–C bonds served as electron/charge bridge accelerate charge/ion transfer, indicating fast reaction kinetics. Electrochemically, ZnSe/C composites show an ultra-long lifetime of 1000 cycles at 5 A g⁻¹ with a capacity of 281 mA h g⁻¹. Furthermore, the electrochemical mechanism of conversion and alloy reactions is revealed by monitoring the phase evolutions and internal impedance changes during the charge–discharge process. Remarkably, the superior cycling life arising from 3D carbon matrix and Zn–O–C bonds demonstrates ZnSe/C composites as reversible and promising anode materials for SIBs. Valence bond bridging such as metal–O–C bonds will have broad prospects for enhancing structural stability and electrochemical properties.

This study aimed to investigate the oxidation mechanism of pyrite crystallographic direction by cutting pyrite samples to expose their (100), (110), and (111) planes. Differences in the oxidation rates of pyrite planes in acid solution were determined. The morphological changes of pyrite were evaluated by scanning electron microscopy and hyperdepth-3D microscopy. The oxidation products of pyrite were examined by Raman spectroscopy and X-ray photoelectron spectroscopy. Results showed that the aqueous oxidation of pyrite produced Fe(OH)₃, Fe₂O₃, Fe₂(SO₄)₃, and S₈ on the surface. Moreover, the morphologies of corrosion patterns differed from one crystal plane to another: square, rectangular, and triangular etch pits were found on the (100), (110), and (111) planes, respectively. The corrosion patterns reflected the symmetrical arrangement of the crystallographic planes in the lattice on which they formed.

Surface modification of InVO₄ nanoparticles on WO₃ plates array films using a dipping–annealing method.