One-pot solution plasma synthesis of tungsten carbide core-shell nanoparticles for efficient conversion of cellulose...

The valorization of lignocellulosic biomass into high-value chemicals has garnered significant attention as a sustainable alternative to fossil-fuel-based processes. In particular, the catalytic conversion of cellulose into lactic acid is of great importance, as it serves as a precursor for biodegradable polylactic acid (PLA). While tungsten (W)-based catalysts are known to promote the retro-aldol reaction necessary for lactic acid production, conventional synthesis of carbide catalysts often requires energy-intensive high-temperature processes. In this study, we demonstrated a facile, one-pot synthesis of tungsten carbide (WC_1-x ) nanoparticles highly dispersed on a carbon matrix using a solution plasma (SP) process. By regulating the pulse frequency during the SP treatment, the W content and dispersion in the carbon support were successfully controlled. Structural analyses revealed that the WC_1-x nanoparticles were encapsulated within carbon shells, preventing oxidation and aggregation. The synthesized WC_1-x /C catalyst exhibited superior catalytic performance for the hydrothermal conversion of cellulose compared to commercial tungsten carbides. Under optimized conditions (190 °C, 48 h), a lactic acid yield of approximately 14.0% was achieved. To assess the catalytic stability, reusability tests and post-reaction characterizations were conducted. While ICP-OES analysis after the first cycle showed negligible W leaching, a significant decrease in yield was observed over four consecutive cycles. XRD and SEM analyses revealed that this deactivation was primarily due to the loss of crystallinity and structural degradation of the WC_1-x phase under harsh hydrothermal conditions. This work provides a novel and rapid route for developing efficient non-noble metal catalysts and clarifies the factors influencing their stability during biomass valorization.