Large-Scale Synthesis and Mechanism of β‑SiC Nanoparticles from Rice Husks by Low-Temperature Magnesiothermic Reduction

Silicon carbide (SiC) nanomaterials have many applications in semiconductor, refractories, functional ceramics, and composite reinforcement due to their unique chemical and physical properties. However, large-scale and cost-effective synthesis of SiC nanomaterials at a low temperature is still challenging. Herein, a low-temperature and scalable process to produce β-phase SiC nanoparticles from rice husks (RHs) by magnesiothermic reduction (MR) at a relative low temperature of 600 °C is described. The SiC nanoparticles could inherit the morphology of biogenetic nano-SiO₂ in RHs with a size of about 20–30 nm. The MR reaction mechanism and role of intermediate species are investigated. The result shows that SiO₂ is first reduced to Mg₂Si in the rapid exothermic process and the intermediate product, Mg₂Si, further reacts with residual SiO₂ and C to produce SiC. Moreover, the SiC shows considerable electromagnetic wave absorption with a minimum reflection loss of −5.88 dB and reflection loss bandwidth < −5 dB of 1.78 GHz. This paper provides a large-scale, cost-effective, environmental friendly, and sustainable process to produce high-quality β-phase SiC nanoparticles from biomass at a low temperature, which is applicable to functional ceramics and optoelectronics

Coordination Environment Engineering of Metal Centers in Coordination Polymers for Selective Carbon Dioxide Electroreduction toward Multicarbon Products

Electrocatalytic carbon dioxide reduction reaction (CO2RR) toward value-added chemicals/fuels has offered a sustainable strategy to achieve a carbon-neutral energy cycle. However, it remains a great challenge to controllably and precisely regulate the coordination environment of active sites in catalysts for efficient generation of targeted products, especially the multicarbon (C2+) products. Herein we report the coordination environment engineering of metal centers in coordination polymers for efficient electroreduction of CO2 to C2+ products under neutral conditions. Significantly, the Cu coordination polymer with Cu–N2S2 coordination configuration (Cu–N–S) demonstrates superior Faradaic efficiencies of 61.2% and 82.2% for ethylene and C2+ products, respectively, compared to the selective formic acid generation on an analogous polymer with the Cu–I2S2 coordination mode (Cu–I–S). In situ studies reveal the balanced formation of atop and bridge *CO intermediates on Cu–N–S, promoting C–C coupling for C2+ production. Theoretical calculations suggest that coordination environment engineering can induce electronic modulations in Cu active sites, where the d-band center of Cu is upshifted in Cu–N–S with stronger selectivity to the C2+ products. Consequently, Cu–N–S displays a stronger reaction trend toward the generation of C2+ products, while Cu–I–S favors the formation of formic acid due to the suppression of C–C couplings for C2+ pathways with large energy barriers