Lignin Nanoparticles-Based Efficient Catalyst for Hydrogen Production and Reduction of Environmental Pollutants

The global imperative for clean and sustainable energy has intensified interest in hydrogen as a high-energy and zero-emission fuel source. Concurrently, water pollution caused by persistent azo dyes continues to pose serious environmental and health risks. Therefore, the development of efficient, sustainable catalysts capable of simultaneously addressing environmental remediation and energy production is of great significance. Herein, lignin nanoparticles (LNPs) were extracted through a solvent–antisolvent precipitation process using acidified tetrahydrofuran and subsequently incorporated into a sodium alginate and crosslinked with Ca2+ ions to form LNPs@SA hydrogel nanocomposites. LNPs and LNPs@SA were employed as bio-based supports for zero-valent copper nanoparticles (Cu0-LNPs and Cu0-LNPs@SA). The structure and composition of the prepared catalysts were characterized using SEM, EDX, XRD, and FTIR. LNPs catalyzed NaBH4 hydrolysis and methanolysis, yielding low activation energy of 54.05 kJ/mol and 25.7 kJ/mol, respectively. The reusability of LNPs@SA in NaBH4 hydrolysis was also evaluated, and the catalyst maintained its effectiveness over four cycles. In the catalytic reduction of methyl orange (MO), Cu0-LNPs achieved 94.4% reduction within 4 min, with a rate constant of kapp= 0.705 min−1. Additionally, Cu0-LNPs@SA outperformed, achieving 99.5% MO removal in 1 min while retaining 99% efficiency over five cycles.