Biomass is a sustainable and renewable resource that can be converted into valuable chemicals, reducing the demand for fossil energy. 5-Hydroxymethylfurfural (HMF), as an important biomass platform molecule, can be converted to high-value-added 2,5-furandicarboxylic acid (FDCA) via a green and renewable electrocatalytic oxidation route under mild reaction conditions, but efficient electrocatalysts are still lacking. Herein, we rationally fabricate a novel self-supported electrocatalyst of core–shell-structured copper hydroxide nanowires@cerium-doped nickel hydroxide nanosheets composite nanowires on a copper mesh (CuH_NWs@Ce:NiH_NSs/Cu) for electrocatalytically oxidizing HMF to FDCA. The integrated configuration of composite nanowires with rich interstitial spaces between them facilitates fast mass/electron transfer, improved conductivity, and complete exposure of active sites. The doping of Ce ions in nickel hydroxide nanosheets (NiH_NSs) and the coupling of copper hydroxide nanowires (CuH_NWs) regulate the electronic structure of the Ni active sites and optimize the adsorption strength of the active sites to the reactant, meanwhile promoting the generation of strong oxidation agents of Ni3+ species, thereby resulting in improved electrocatalytic activity. Consequently, the optimal CuH_NWs@Ce:NiH_NSs/Cu electrocatalyst is able to achieve a HMF conversion of 98.5% with a FDCA yield of 97.9% and a Faradaic efficiency of 98.0% at a low constant potential of 1.45 V versus reversible hydrogen electrode. Meanwhile, no activity attenuation can be found after 15 successive cycling tests. Such electrocatalytic performance suppresses most of the reported Cu-based and Ni-based electrocatalysts. This work highlights the importance of structure and doping engineering strategies for the rational fabrication of high-performance electrocatalysts for biomass upgrading.
Indirect photodegradation is an important pathway for the reduction of steroid estrogens in sunlit surface waters. Nevertheless, the kinetics and mechanisms governing the interaction between coexisting carbonyl compounds and estrogens under visible light (Vis) remain unexplored. This study systematically investigates the Vis-induced photodegradation of 17 β -estradiol (E2) in the presence of five specific carbonyl compounds—biacetyl (BD), acetone, glyoxal, pyruvic acid, and benzoquinone . The results demonstrate that, among these compounds, only BD significantly enhanced the photodegradation of E2 under Vis irradiation (λ > 400 nm). The pseudo-first order photodegradation rate constants ( k 1 ) of E2 in the Vis/BD system were 0.025 min −1 and 0.076 min −1 in ultrapure water and river water, respectively. The enhancing effect of BD was found to be pH-dependent, increasing the pH from 3.0 to 11.0 resulted in a 76% reduction in the k 1 value of E2 in the Vis/BD system. Furthermore, the presence of humic acid , NO 3 − , or HCO 3 − led to an increase of more than 35% in the k 1 value of E2, while NO 2 − exerted a pronounced inhibitory effect, resulting in a 92% decrease. Peroxyacetyl and peroxymethyl radicals, derived from BD in a yield ratio of 9, played a crucial role in the degradation of E2. These peroxyl radicals primarily targeted electron-rich hydroxyl sites of E2, initiating hydroxylation and ring-opening reactions that culminated in the formation of acidic byproducts. Notably, toxicity evaluation indicates that these hydroxylated and acidic products exhibited lower toxicity than the parent compound E2. This study highlights the important role of peroxyl radicals in estrogen degradation within aquatic environment, and also helps to design efficient visible light-responsive photo-activators for the treatment of estrogen-contaminated waters.
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