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_x) 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_x 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%.