Coenzyme A-regulated Pd nanocatalysts for formic acid-mediated reduction of hexavalent chromium

Coenzyme A (CoA), as a cofactor of enzymes in bacteria, is involved in various reactions of intermediary metabolism owing to its thiol groups. Herein we develop a facile CoA-assisted approach for the green synthesis of nonspherical Pd nanoparticles (NPs) with grain boundaries, which potentially serve as the catalytic hot spots. As-prepared CoA-Pd nanocomposites were applied for the catalytic reduction of highly toxic chromium (VI) by using formic acid (FA) as the reductant with the highest reduction rate of 2.45 mmol mg−1 min−1 (50 °C), which is superior to recently reported homogenous and heterogeneous Pd-based catalysts. Through the characterizations by UV-vis, FTIR, TEM, XRD and XPS in combination with DFT calculations, CoA plays an essential role in regulating the growth of Pd NPs, resulting in the formation of nonspherical morphology at high [Na2PdCl4]/[CoA]. The catalytic activity of CoA-Pd was also assessed for the hydrogenation reduction of p-nitrophenol and the degradation of trichloroethylene (TCE) in the presence of formic acid. This strategy expands eco-friendly synthetic techniques to design highly efficient nanocatalysts to meet the requirement of catalytic reduction of Cr(VI) and other types of FA-mediated hydrogenation reactions.