02198nas a2200241   4500008004100000022001200041245012300053210006900176260000800245300000700253490000800260520135300268653002501621653001601646653002801662653002001690100002701710700002901737700001601766700001501782700003001797856012901827       2018                        eng d  a974362600aSubtle interaction between Ag and O 2 : a near ambient pressure UV photoelectron spectroscopy (NAP-UPS) investigations0 aSubtle interaction between Ag and O 2 a near ambient pressure UV  cMAR  a300 v1303 aThe Ag-O2 interaction, which is at the center-stage of Ag-catalyzed partial oxidation reactions, is
studied with NAP-UPS up to 0.2 mbar O2 pressure between 295 and 550 K. Three temperature regimes were
identified for distinct Ag-O2 interaction, which are (a) 295–390 K, where mainly dissociative chemisorption of
O2 happens, (b) 390–450 K, where diffusion of O-atoms into the sub-surfaces of Ag is prominent, and (c) >450
K, where metastable oxide forms on polycrystalline Ag surfaces. The work function (WF) of Ag changed from
4.95 (≤390 K) to 5.30 eV (390–450 K), and then to 5.7 eV (≥450 K) at 0.1 mbar O2 pressure. Oxygen population
in the sub-surfaces imparts crucial modifications to Ag at 390–450 K; it makes the surface to be electron-deficient
that relates to the change in the WF of Ag and facilitates the formation of space charge layer on Ag surface.
Oxygen adsorbed on such modified Ag-surfaces is electrophilic in nature, and this appears at a higher binding
energy in core level XPS than the chemisorbed oxygen on metallic Ag. This is supported by angle-dependent
NAP-XPS studies. The subsurface population of oxygen in Ag no longer persists at >410 K when the O2 supply
is removed. A high ratio of antibonding/bonding O 2p bands suggests the unique silver-oxygen interaction under
the measurement conditions.10aElectronic Structure10aepoxidation10aheterogeneous catalysis10aSurface Science1 aGhosalya, Manoj, Kumar1 aReddy, Kasala, Prabhakar1 aJain, Ruchi1 aRoy, Kanak1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/subtle-interaction-between-ag-and-o-2-near-ambient-pressure-uv-photoelectron-spectroscopy02553nas a2200265   4500008004100000022001400041245009700055210006900152260000800221300001100229490000800240520168600248653002701934653002801961653000901989653000801998653002002006100001702026700002102043700001602064700002302080700002602103700003002129856012802159       2023                        eng d  a1385-894700aCo3O4 for sustainable CO2 reduction and possible fine-tuning towards selective CO production0 aCo3O4 for sustainable CO2 reduction and possible finetuning towa  cSEP  a1444590 v4713 a<p>Two main challenges involved in heterogeneous catalytic CO2 reduction are: (a) decreasing the consumption of H2 to the minimum required level with possibly the maximum CO2 conversion, and (b) concurrently enhancing the selectivity of the desired CO, at the cost of methane. Towards meeting these two challenges, Co3O4 spinel has been identified as a potential catalyst and it exhibits predominant CO selectivity &gt; 673 K at atmospheric pressure. CO2 conversion begins &gt; 523 K, with 100% CO selectivity observed &gt; 673 K with CO2:H2 = 3:2. Current work shows a sustainable catalytic CO2 conversion to 100% CO selectivity with Co3O4-Nanocube (NC). Critically, CO selectivity and yield is observed to increase at the cost of methane with smaller amount of H2. 1:1 and 3:2 CO2:H2 ratio exhibits 88-100% CO selectivity with 24-32.5% CO2 conversion between 623 and 823 K. Irrespective of the input CO2:H2, ratio of CO2:H2 uptake changes from around 1:3 at 523 K to 1:1-1.5 at 823 K with concurrent production of significant methane to predominant CO, respectively. Surface electronic state changes was explored by near ambient pressure photoelectron spectroscopy, and the results suggests that Co3O4 is the active phase that promotes CO2 reduction selectively to CO. Broadening observed with the vibrational feature of the CO2 molecules at high temperature underscores the heterogeneous character of the catalyst surface, under operating conditions, due to changing electron density. By optimizing the gas hourly space velocity (GHSV), H2-lean CO2:H2 ratio, and the reaction temperature/pressure, 100% CO selectivity could be broadened to a range of operating conditions.</p>
10aCarbon neutral economy10aheterogeneous catalysis10aRWGS10aSDG10aSurface Science1 aRanjan, Ravi1 aTekawadia, Jyoti1 aJain, Ruchi1 aMhamane, Nitin, B.1 aRaja, Thirumalaiswamy1 aGopinath, Chinnakonda, S.  uhttps://library.ncl.res.in/content/co3o4-sustainable-co2-reduction-and-possible-fine-tuning-towards-selective-co-production