Chemical deactivation of Cu-SAPO-18 deNO_x catalyst caused by basic inorganic contaminants in diesel exhaust

Contaminants(K,Na,Ca,and Mg)were introduced into Cu-SAPO-18 via incipient wetness impregnation to investigate their effect on the selective catalytic reduction of NOx with NH3(NH3-SCR)over Cu-SAPO-18.After the introduction of contaminants into Cu-SAPO-18,the quantity of acidic sites and Cu^2+ species in catalyst decreases owing to the replacement of H^+ and Cu^2+ by K^+,Na^+,Ca^2+,and Mg^2+.Furthermore,the loss of isolated Cu^2+ induces the generation of CuO and CuAl2O4-like phases,which causes further loss in the Brunauer-Emmett-Teller surface area of the catalyst.Consequently,the deNOx performance of the contaminated Cu-SAPO-18 catalysts drops.Such decline in NH3-SCR performance becomes more pronounced by increasing the contaminant contents from 0.5 to 1.0 mmol/gcatal.In addition,the deactivation influence of the contaminants on Cu-SAPO-18 is presented in the order of K>Na>Ca>Mg,which is consistent with the order of reduction of acidic sites.To a certain degree,the effect of the acidic sites on the deactivation of Cu-SAPO-18 might be more significant than that of isolated Cu2+ and the catalyst framework.Moreover,kinetic analysis of NH3-SCR was conducted,and the results indicate that there is no influence of contaminants on the NH3-SCR mechanism.

Size control and electronic manipulation of Ru catalyst over B,N codoped carbon network for high-performance hydrogen evolution reaction

Exploring highly efficient Pt-free catalysts for hydrogen evolution reaction(HER)is of great importance for hydrogen(H2)production.Herein,a novel HER electrocatalyst having abundant ultra-small(2–3 nm)Ru electronically confined by a B,N codoped polar carbon surface(Ru/(B-N)-PC)was constructed.The Ru/(B-N)-PC catalyst exhibits a low overpotential of 15 mV at the current density of 10 mA·cm^(−2),a low Tafel slope of 22.6 mV·dec^(−1),superior durability,which outperforms the benchmark Pt/C catalyst.Both experimental characterizations and theory calculations suggest that an electron communication established between B,N co-doped carbon surface and ultra-small Ru nanoparticles with electrons transferred from N atoms to Ru and backtransferred from Ru to B atoms,which exerts a moderate electronic modification of Ru.This,in turn,affords a modest H adsorption energy and a lower H2O dissociation barrier,leading to the high-performance hydrogen evolution reaction.The work provides meaningful insight into the size control and electronic modulation of Ru catalyst for intrinsic HER activity improvement.