Effective removal of Cr(VI) in aqueous solutions using Caulis lonicerae residue fermented by Phanerochaete chrysosporium.

Cr(VI) is one of the most common environmental pollutants. The non-biodegradable Cr(VI) in aqueous solution accumulates along the food chain and damages the health of plant, animal, and human. In this study, solid-state fermentation technology was used to treat Caulis lonicerae residue to improve its adsorption capacity for Cr(VI). Caulis lonicerae can be used to extract the active ingredients such as organic acids, flavonoids, and triterpenoid saponins that have various effects including anti-oxidation and immune boosting. However, there is no proper treatment for large amount of residue left after extraction. The Phanerochaete chrysosporium was inoculated into the residue for solid-state fermentation, and the adsorption capacity of C. lonicerae residue before (CLr) and after fermentation (FCLr) regarding Cr(VI) adsorption was compared. In the range of 40-120 mg/L Cr(VI), the adsorption capacity of FCLr was significantly higher than that of CLr. The scanning electron microscopy (SEM) results exhibited a rougher surface of FCLr. The Fourier-transform infrared spectroscopy (FTIR) results revealed that the structure of FCLr was affected by the combination of Cr(VI), and the multiple functional groups interacted with Cr(VI) (such as -OH, C-H, C = O, C-O-C, and C-O). The adsorption capacity could reach 48.91 mg/g and the Cr(VI) removal percentage may reach 98.07% for FCLr increased by 28.24% through fermentation.

Manganese-facilitated dynamic active-site generation on Ni2P with self-termination of surface reconstruction for urea oxidation at high current density.

Electrochemical urea oxidation reaction (UOR) suffers from sluggish reaction kinetics due to its complex 6-electron transfer processes combined with conversion of complicated intermediates, severely retarding the overall energy conversion efficiency. Herein, manganese-doped nickel phosphide nanosheets (Mn-Ni2P) are constructed and employed for driving UOR. Comprehensive analysis deciphers that Mn doping could efficiently accelerate the surface reconstruction of Mn-Ni2P electrode, generating highly reactive NiOOH-MnOOH heterostructure with local nucleophilic and electrophilic regions. Such unique structure could accelerate the targeted adsorption and activation of C and N atoms, promoting fracture of CN bond in urea. In addition, moderate Mn doping could efficiently enhance the adsorption capacities of urea molecules and some key intermediates, and minish the energy barrier for *CO2 desorption, accelerating refreshing of the catalyst. Consequently, the Mn-Ni2P electrode exhibits excellent UOR catalytic activity, achieving an industrial-level current density of 1000 mA cm-2 at 1.46 V (vs. RHE).

Deciphering the active origin for urea oxidation reaction over nitrogen penetrated nickel nanoparticles embedded in carbon nanotubes.

Urea electrooxidation with favorable thermodynamic potential is highly anticipated but suffering from sluggish kinetics. Deciphering the activity origin and achieving rational structure design are pivotal for developing highly efficient electrocatalyst for urea oxidation reaction (UOR). Herein, nitrogen penetrated nickel nanoparticles confined in carbon nanotubes (Ni-NCNT) is successfully achieved to drive UOR. Active origin of Ni-NCNT is decoded to be the in-situ generated Ni2+δO(OH)ads according to comprehensive analysis. The electrophilic Ni2+δ and protophilic OHads could targeted capture O and H atoms from urea, respectively, achieving molecule activation and accelerating the subsequent proton coupled electron transfer reactions. Nitrogen penetration is identified to promote prior formation of Ni2+δO(OH)ads and push up the d band center of Ni-NCNT, enhancing urea adsorption and subsequent molecule cleavage reactions. As a result, Ni-NCNT exhibits superior UOR performance. This work supplies valuable insights for the rational design and construction of efficient nickel-based catalyst for driving UOR.