Modification of structured bio‑carbon derived from spongin-based scaffolds with nickel compounds to produce a functional catalyst for reduction and oxidation reactions: Potential for use in environmental protection

Highlights: • Marine sponges as a biomimetic source of biocarbons • Prepared biocarbons were modified with Ni species to obtain functional materials. • Study of morphological and physicochemical properties of prepared composites • Ni-modified biocarbons as functional materials for catalytic use. • New catalysts for oxidation or reduction reactions of phenolic compounds Three different 3D fibrous-like NiO/Ni(OH)₂/Ni‑carbonized spongin-based materials were prepared via a simple sorption–reduction method. Depending on the support used, the catalysts were composed of carbon, nickel oxide, nickel hydroxide and zero-valent nickel, with the surface content of the nickel-containing phase in the range 15.2–26.0 wt%. Catalytic studies showed promising activity in the oxidation of phenolic compounds in water and in the reduction of 4-nitrophenol. The oxidation efficiency depends on the substrate used and ranges from 80% for phenol at pH 2 to 99% for 4-chlorophenoxyacetic acid (4-CPA) and methylchlorophenoxypropionic acid (MCPP). In the reduction reaction, all catalysts exhibited superior activity, with rate constants in the range 0.648–1.022 min^-1. The work also includes a detailed investigation of reusability and kinetic studies.