Density functional theory study of active sites and reaction mechanism of ORR on Pt surfaces under anhydrous conditions

Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a temperature>100℃.Here,by employing density functional theory calculations,we studied ORR on flat and stepped Pt(111)surfaces with both(110)and(100)type of steps.We found that,in contrast to ORR under hydrous conditions,(111)terrace sites are not active for ORR under anhydrous conditions,because of weakened binding of ORR intermediates induced by O*accumulation on the surface.On the other hand,step edges,which are generally not active for ORR under hydrous conditions,are predicted to be the active sites for ORR under anhydrous conditions.Among them,(110)type step edge with a unique configuration of accumulated O stabilizes O_(2)adsorption and facilitates O_(2)dissociation,which lead an overpotential<0.4 V.To improve ORR catalysts in high-temperature PEMFCs,it is desirable to maximize(110)step edge sites that present between two(111)facets of nanoparticles.

Graph theory approach to determine configurations of multidentate and high coverage adsorbates for heterogeneous catalysis

Heterogeneous catalysts constitute a crucial component of many industrial processes,and to gain an understanding of the atomicscale features of such catalysts,ab initio density functional theory is widely employed.Recently,growing computational power has permitted the extension of such studies to complex reaction networks involving either high adsorbate coverages or multidentate adsorbates,which bind to the surface through multiple atoms.Describing all possible adsorbate configurations for such systems,however,is often not possible based on chemical intuition alone.To systematically treat such complexities,we present a generalized Python-based graph theory approach to convert atomic scale models into undirected graph representations.These representations,when combined with workflows such as evolutionary algorithms,can systematically generate high coverage adsorbate models and classify unique minimum energy multidentate adsorbate configurations for surfaces of low symmetry,including multi-elemental alloy surfaces,steps,and kinks.