Steam reforming of acetic acid over Ni/biochar of low metal-loading:Involvement of biochar in tailoring reaction intermediates renders superior catalytic performance

Biochar is a reactive carrier as it may be partially gasified with steam in steam reforming,which could influence the formation of reaction intermediates and modify catalytic behaviors.Herein,the Ni/biochar as well as two comparative catalysts,Ni/Al_(2)O_(3) and Ni/SiO_(2),with low nickel loading(2%(mass))was conducted to probe involvement of the varied carriers in the steam reforming.The results indicated that the Ni/biochar performed excellent catalytic activity than Ni/SiO_(2) and Ni/Al_(2)O_(3),as the biochar carrier facilitated quick conversion of the -OH from dissociation of steam to gasify the oxygen-rich carbonaceous intermediates like C=O and C-O-C,resulting in low coverage while high exposure of nickel species for maintaining the superior catalytic performance.In converse,strong adsorption of aliphatic intermediates over Ni/Al_(2)O_(3) and Ni/SiO_(2) induced serious coking with polymeric coke as the main type(21.5%and 32.1%,respectively),which was significantly higher than that over Ni/biochar(3.9%).The coke over Ni/biochar was mainly aromatic or catalytic type with nanotube morphology and high crystallinity.The high resistivity of Ni/biochar towards coking was due to the balance between formation of coke and gasification of coke and partially biochar with steam,which created developed mesopores in spent Ni/biochar while the coke blocked pores in Ni/Al_(2)O_(3) and Ni/SiO_(2) catalysts.

Photocatalysis vs adsorption by metal oxide nanoparticles

Background:Metal oxide(MO)nanomaterials and related nanocomposites have been extensively studied for their potential use in water treatment.Because of their controlled morphologies,texture qualities,variable surface chemistry,distinct crystalline nature,high stability,and tunable band edges,MO nanostructured materials are highly selective towards deleting organic contaminants and heavy metal ions via adsorption and semiconductor photocatalysis.Metal-enhanced photocatalysis has recently received increasing interest,mainly due to the ability of the metal to directly or indirectly degrade pollutants.A diverse selection of MOs,with titanium dioxide(Ti O2),zinc oxide(Zn O),iron oxides(IO),and tungsten(W),as well as graphene-MOs nanocomposites with variable structure,crystalline,and morphological properties,offers a powerful platform for the growth of effective catalysts.Methods:The current work discusses novel advancements and potential for the removal of adsorptive and photocatalytic degradation of organic compounds(phenolic,pesticide molecules,dyes,and so on)as well as heavy metal ions using semiconductor materials.A photocatalyst based on a MO-scheme heterostructure can manage the appropriate conduction band(CB)and valence band(VB)locations,securing considerable redox aptitude.This review should be of interest to the broad readership dealing with applied and fundamental aspects of water treatments and material sciences.Various strategies including surface modification,plasmonic enhancement,and metal cocatalysts have been introduced to enhance photocatalytic performance.Significant findings:The current article discussed the significantly utilized synthesis strategies and mechanism of heterojunction photocatalysts using a Z-scheme.Furthermore,adsorption sections guarantee that mercury,chromium,cadmium,arsenic,and lead-based ions are successfully removed from polluted water via the adsorption route.Numerous characteristics,such as concentration,coexisting ions,p H,and kind of chemical have converged to comprehend the adsorption procedure.The technological challenges and future approaches are discussed to maximize the photocatalytic and adsorption efficacy and the reusability of MO-based nanomaterials for water security.