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

Abstract

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%.

Universal Kinetic Mechanism Describing CO2 Photoreductive Yield and Selectivity for Semiconducting Nanoparticle Photocatalysts

“…A set of three commercially available semiconducting nanoparticle materialsTiO 2 : Aeroxide P25 (≥99.5% trace metals basis), SnO 2 : US Research Nanomaterials; super fine 18 nm (≥99.99%) and SiC: US Research Nanomaterials; laser synthesized 18 nm (≥99%)were selected for their previous use (specifically the case for TiO 2 ), photostability, and activity toward CO 2 reduction. Each one of the C1 products has been observed as the result of CO 2 photocatalytic reduction on TiO 2 , SnO 2 , − and SiC, , though under disparate reaction conditions. These photocatalysts are expected to show a range of activity attributed to the heterogeneity in their band gaps, valance- and conduction-band positions, surface chemistry, and formation of unique semiconductor–metal interfaces, which also affects charge separation, modifies light absorption, and creates new and modified adsorption sites .…”

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

“…Very recently, the ability of metal-free SiC to reduce CO 2 to methane has been further investigated. While Lin theoretically predicted that the reaction is highly favored on the SiC(111) surface with respect to the hydroxylated counterpart, Sun’s group prepared 3C-SiC nanoparticles able to promote the CO 2 reaction with 90% methane selectivity . They prepared their photocatalytic material on gram scale through powder ball-milling producing 3C-SiC NPs bearing an amorphous SiO x outer shell and inducing abundant surface states.…”

“…While Lin theoretically predicted that the reaction is highly favored on the SiC (111) surface with respect to the hydroxylated counterpart, 734 Sun's group prepared 3C-SiC nanoparticles able to promote the CO 2 reaction with 90% methane selectivity. 735 They prepared their photocatalytic material on gram scale through powder ballmilling producing 3C-SiC NPs bearing an amorphous SiO x outer shell and inducing abundant surface states. These latter are known to capture the photogenerated electrons thus avoiding charge recombination while silicon oxide preserves the 3C-SiC core from corrosion under visible light.…”

Effect of hBN on Corrosion and Wear Performances of DC Electrodeposited NiW and NiW–SiC on Brass Substrates

“…The performance of passive layer in corrosive media is affected by many factors, such as pH, temperature, and dissolved oxygen content [40][41][42][43]. The increase in corrosion potential of NiW toward positive values with the addition of SiC could be attributed to a uniform distribution of SiC particles within the NiW, surface oxidation of SiC particles or presence of SiO 2 in the interplanar layers of individual SiC [32,33]. As well, formation of double layer of NiWO 4 due to the oxidation of the NiW when exposed to corrosive media.…”