N2O decomposition and reduction on Co-MOR, Fe-MOR and Ni-MOR catalysts: in situ UV–vis DRS and operando FTIR investigation. An insight on the reaction pathways

Co-, Fe- or Ni-exchanged Na-MOR (Si/Al = 9.2) were prepared by ion-exchange method. The catalytic activity for N2O decomposition in the absence or in the presence of NO and for N2O reduction with CH4 in the absence of O2 (CRN2O), or in the presence of O2 (SCRN2O) was investigated. The catalytic measurements were performed in a flow apparatus with GC analysis of reactants and products. On Fe-MOR, in situ FTIR and UV–vis characterization evidenced coordinatively unsaturated sites (c.u.s.) Fe2+ arising from two families of Fe3+ dimers with different reducibility. Characterization and catalytic results combined with operando FTIR experiments gave an insight into the transition metal ion (tmi) species working during N2O abatement and into the reaction pathways. For N2O decomposition the activity order was Co-MOR > Fe-MOR in the absence of NO and Fe-MOR ≥ Co-MOR in the presence of NO, whereas Ni-MOR was always inactive. The decomposition occurred via redox mechanism passing through the formation of activated surface oxygen species, Oads *. The quasi-oxidic character of this activated oxygen in the Fe3+-O(1+δ)−—Fe(2+δ)+ intermediates with respect to the oxyl character of that in Co3+O‒ intermediates accounted for the lower activity and for the activity enhancement by NO addition to the feed of Fe-MOR with respect to Co-MOR. In Ni-MOR, both isolated or dimeric Ni2+ species were unable to be oxidized by N2O yielding Oads *. For N2O reduction, (CRN2O) and (SCRN2O), the activity order was Fe-MOR > Ni-MOR > Co-MOR. On all catalysts operando FTIR experiments revealed CHxOy intermediates (methoxy, formaldehyde and two types of formate species). The investigation of surface species changing the addition order of the reactants evidenced that the formation of CHxOy intermediates was favored on Co-MOR by pre-saturation with N2O, that yielded Co3+O− able to activate CH4, whereas on Ni-MOR by pre-saturation with CH4, that reduced Ni2+ dimers to Ni+ dimers, able to activate N2O. On Fe-MOR, the Fe2+ dimers formed during activation behaved as Co2+, whereas the Fe2+ dimers formed by reduction with CH4 behaved as Ni+ dimers. The formation and the stability of Oads * surface species were key factors for N2O decomposition and reduction pathways. These factors were affected by the mobility of the tmi electrons, that depends on the oxidation state, nuclearity and location in MOR framework of tmi. © 2018 Elsevier B.V

N2O decomposition on CoOx, CuOx, FeOx or MnOx supported on ZrO2: The effect of zirconia doping with sulfates or K+ on catalytic activity

Zirconia doped with sulfates or K+ were prepared by impregnation with (NH4)2SO4, or KNO3 aqueous solutions. MeOx/ZrO2 and MeOx/doped-ZrO2 catalysts (Me=Co, Cu, Fe or Mn) were prepared by wet impregnation of zirconia and doped-zirconia supports. The effect of doping on MeOx properties was studied by XRD, UV-vis DRS, H2-TPR and FTIR and the influence of doping on the catalytic activity for N2O decomposition was investigated under ideal conditions (N2O in He) and under real reaction conditions (addition of NO, O2, and water vapour to the reactant mixture).Characterization results indicated that all samples contained mainly dispersed Men+ species interacting with the support. In MeOx/sulfated-ZrO2 the doping with electron-withdrawing sulfates stabilized the Men+ oxidation state. In CoOx/K-ZrO2 samples the doping with electron-releasing K+ increased the poly-nuclear CoOx reducibility. FTIR characterization suggested that the electron-donor capacity of Co2+ site had the order CoOx/sulfated-ZrO

CoOx and FeOx supported on ZrO2 for the simultaneous abatement of NOx and N2O with C3H6 in the presence of O2

MeOx/ZrO2 (Me = Co and Fe) catalysts were studied for the simultaneous selective catalytic reduction of NO and N2O in the presence of O2 using C3H6 as reducing agent (SCRsim). To give a better insight in the simultaneous process we investigated the reactions related to SCRsim (SCRN2O, SCRNO, N2O decomposition and C3H6 combustion) as well as the abatements in the absence of O2 (CRsim, CRN2O, CRNO). Catalytic results showed that, in the presence of O2 excess, CoOx/ZrO2 and FeOx/ZrO2 catalysts were scarcely active and unselective for the separate NO and N2O abatements with C3H6 and are ineffective for their simultaneous abatement. Because C3H6 preferentially reacted with O2, NO was poorly reduced and N2O was abated, at a temperature above that of complete C3H6 conversion, via both SCRN2O and decomposition. Conversely, in the absence of O2 in the feed, on both catalysts NO and N2O were efficiently reduced by C3H6, but undesired by-products formed. The activity for SCRsim strongly depended on the C3H6/O2 feeding ratio. With suitable feeding mixture O2 was completely consumed and the residual propene efficiently and simultaneously reduced NO and N2O, with negligible formation of by-products. In hydrothermal conditions both catalysts were slightly and reversibly deactivated. Characterization by XRD, UV–vis DRS and FTIR after catalytic experiments showed that dispersed Co2+ and Fe3+ species were stable on zirconia surface and that no significant segregation phenomena occurred in hydrothermal conditions

A comprehensive comparison of dye-sensitized NiO photocathodes for solar energy conversion

We investigated a range of different mesoporous NiO electrodes prepared by different research groups and private firms in Europe to determine the parameters which influence good quality photoelectrochemical devices. This benchmarking study aims to solve some of the discrepancies in the literature regarding the performance of p-DSCs due to differences in the quality of the device fabrication. The information obtained will lay the foundation for future photocatalytic systems based on sensitized NiO so that new dyes and catalysts can be tested with a standardized material. The textural and electrochemical properties of the semiconducting material are key to the performance of photocathodes. We found that both commercial and non-commercial NiO gave promising solar cell and water-splitting devices. The NiO samples which had the two highest solar cell efficiency (0.145% and 0.089%) also gave the best overall theoretical H2 conversion

A comprehensive comparison of dye-sensitized NiO photocathodes for solar energy conversion

International audienceWe investigated a range of different mesoporous NiO electrodes prepared by different research groups and private firms in Europe to determine the parameters which influence good quality photoelectrochemical devices. This benchmarking study aims to solve some of the discrepancies in the literature regarding the performance of p-DSCs due to differences in the quality of the device fabrication. The information obtained will lay the foundation for future photocatalytic systems based on sensitized NiO so that new dyes and catalysts can be tested with a standardized material. The textural and electrochemical properties of the semiconducting material are key to the performance of photocathodes. We found that both commercial and non-commercial NiO gave promising solar cell and water-splitting devices. The NiO samples which had the two highest solar cell efficiency (0.145% and 0.089%) also gave the best overall theoretical H2 conversion

Delayed colorectal cancer care during covid-19 pandemic (decor-19). Global perspective from an international survey

Background The widespread nature of coronavirus disease 2019 (COVID-19) has been unprecedented. We sought to analyze its global impact with a survey on colorectal cancer (CRC) care during the pandemic. Methods The impact of COVID-19 on preoperative assessment, elective surgery, and postoperative management of CRC patients was explored by a 35-item survey, which was distributed worldwide to members of surgical societies with an interest in CRC care. Respondents were divided into two comparator groups: 1) ‘delay’ group: CRC care affected by the pandemic; 2) ‘no delay’ group: unaltered CRC practice. Results A total of 1,051 respondents from 84 countries completed the survey. No substantial differences in demographics were found between the ‘delay’ (745, 70.9%) and ‘no delay’ (306, 29.1%) groups. Suspension of multidisciplinary team meetings, staff members quarantined or relocated to COVID-19 units, units fully dedicated to COVID-19 care, personal protective equipment not readily available were factors significantly associated to delays in endoscopy, radiology, surgery, histopathology and prolonged chemoradiation therapy-to-surgery intervals. In the ‘delay’ group, 48.9% of respondents reported a change in the initial surgical plan and 26.3% reported a shift from elective to urgent operations. Recovery of CRC care was associated with the status of the outbreak. Practicing in COVID-free units, no change in operative slots and staff members not relocated to COVID-19 units were statistically associated with unaltered CRC care in the ‘no delay’ group, while the geographical distribution was not. Conclusions Global changes in diagnostic and therapeutic CRC practices were evident. Changes were associated with differences in health-care delivery systems, hospital’s preparedness, resources availability, and local COVID-19 prevalence rather than geographical factors. Strategic planning is required to optimize CRC care