Highly Selective Photocatalytic CO₂ Reduction to CH₄ by Ball-Milled Cubic Silicon Carbide Nanoparticles under Visible-Light Irradiation

The ultimate goal of photocatalytic CO₂ reduction is to achieve high selectivity for a single product with high efficiency. One of the most significant challenges is that expensive catalysts prepared through complex processes are usually used. Herein, gram-scale cubic silicon carbide (3C-SiC) nanoparticles are prepared through a top-down ball-milling approach from low-priced 3C-SiC powders. This facile mechanical milling strategy ensures large-scale production of 3C-SiC nanoparticles with an amorphous silicon oxide (SiO) shell and simultaneously induces abundant surface states. The surface states are demonstrated to trap the photogenerated carriers, thus remarkably enhancing the charge separation, while the thin SiO shell prevents 3C-SiC from corrosion under visible light. The unique electronic structure of 3C-SiC tackles the challenge associated with low selectivity of photocatalytic CO₂ reduction to C₁ compounds. In conjugation with efficient water oxidation, 3C-SiC nanoparticles can reduce CO₂ into CH₄ with selectivity over 90%.