Selectivity control of photocatalytic CO_(2) reduction over ZnS-based nanocrystals:A comparison study on the role of ionic cocatalysts

Taking copper doped ZnS(ZnS:Cu)nanocrystals as the main body of photocatalyst,the influence of different base transition metal ions(M^(2+)=Ni^(2+),Co^(2+),Fe^(2+)and Cd^(2+))on photocatalytic CO_(2)reduction in inorganic reaction system is investigated.Confined single-atom Ni^(2+),Co^(2+),and Cd^(2+)sites were created via cation-exchange process and enhanced CO_(2)reduction,while Fe^(2+)suppressed the photocatalytic activity for both water and CO_(2)reduction.The modified ZnS:Cu photocatalysts(M/ZnS:Cu)demonstrated tunable product selectivity,with Ni^(2+)and Co^(2+)showing high selectivity for syngas production and Cd^(2+)displaying remarkable formate selectivity.DFT calculations indicated favorable H adsorption free energy on Ni^(2+)and Co^(2+)sites,promoting the hydrogen evolution reaction.The selectivity of CO_(2)reduction products was found to be sensitive to the initial intermediate adsorption states.*COOH formed on Ni^(2+)and Co^(2+)while*OCHO formed on Cd^(2+),favoring the production of CO and HCOOH as the main products,respectively.This work provides valuable insights for developing efficient solar-to-fuel platforms with controlled CO_(2)reduction selectivity.

Competing esterification and oligomerization reactions of typical long-chain alcohols to secondary organic aerosol formation

Organosulfate (OSA) nanoparticles,as secondary organic aerosol (SOA) compositions,are ubiquitous in urban and rural environments.Hence,we systemically investigated the mechanisms and kinetics of aqueous-phase reactions of 1-butanol/1-decanol (BOL/DOL) and their roles in the formation of OSA nanoparticles by using quantum chemical and kinetic calculations.The mechanism results show that the aqueous-phase reactions of BOL/DOL start from initial protonation at alcoholic OH^(-)groups to form carbenium ions (CBs),which engage in the subsequent esterification or oligomerization reactions to form OSAs/organosulfites (OSIs) or dimers.The kinetic results reveal that dehydration to form CBs for BOL and DOL reaction systems is the rate-limiting step.Subsequently,about 18%of CBs occur via oligomerization to dimers,which are difficult to further oligomerize because all reactive sites are occupied.The rate constant of BOL reaction system is one order of magnitude larger than that of DOL reaction system,implying that relative short-chain alcohols are more prone to contribute OSAs/OSIs than long-chain alcohols.Our results reveal that typical long-chain alcohols contribute SOA formation via esterification rather than oligomerization because OSA/OSI produced by esterification engages in nanoparticle growth through enhancing hygroscopicity.

Assessing the role of mineral particles in the atmospheric photooxidation of typical carbonyl compound

Mineral particles are ubiquitous in the atmosphere and exhibit an important effect on the photooxidation of volatile organic compounds(VOCs).However,the role of mineral particles in the photochemical oxidation mechanism of VOCs remains unclear.Hence,the photooxi-dation reactions of acrolein(ARL)with OH radical(OH)in the presence and absence of SiO_(2) were investigated by theoretical approach.The gas-phase reaction without SiO_(2) has two distinct pathways(H-abstraction and OH-addition pathways),and carbonyl-H-abstraction is the dominant pathway.In the presence of SiO_(2),the reaction mechanism is changed,i.e.,the dominant pathway from carbonyl-H-abstraction to OH-addition to carbonyl C-atom.The energy barrier of OH-addition to carbonyl C-atom deceases 21.33 kcal/mol when SiO_(2) is added.Carbonyl H-atom of ARL is occupied by SiO_(2) via hydrogen bond,and carbonyl C-atom is ac-tivated by SiO_(2).Hence,the main product changes from H-abstraction product to OH-adduct in the presence of SiO_(2).The OH-adduct exhibits a thermodynamic feasibility to yield HO_(2) radical and carboxylic acid via the subsequent reactions with O_(2),with implications for O 3 formation and surface acidity of mineral particles.