Platinum (Pt) nanocrystals have demonstrated to be an effective catalyst in many heterogeneous catalytic processes. However, pioneer facets with highest activity have been reported differently for various reaction systems. Although Pt has been the most important counter electrode material for dye-sensitized solar cells (DSCs), suitable atomic arrangement on the exposed crystal facet of Pt for triiodide reduction is still inexplicable. Using density functional theory, we have investigated the catalytic reaction processes of triiodide reduction over {100}, {111} and {411} facets, indicating that the activity follows the order of Pt(111) > Pt(411) > Pt(100). Further, Pt nanocrystals mainly bounded by {100}, {111} and {411} facets were synthesized and used as counter electrode materials for DSCs. The highest photovoltaic conversion efficiency of Pt(111) in DSCs confirms the predictions of the theoretical study. These findings have deepened the understanding of the mechanism of triiodide reduction at Pt surfaces and further screened the best facet for DSCs successfully.

Electrochemical reduction of aqueous CO2 into formate is subject to poor selectivity and low current density with conventional Sn-based catalysts owing to the inert nature of CO2 molecules and the low number of active sites.

No abstract

The efficient electrocatalysts for many heterogeneous catalytic processes in energy conversion and storage systems must possess necessary surface active sites. Here we identify, from X-ray photoelectron spectroscopy and density functional theory calculations, that controlling charge density redistribution via the atomic-scale incorporation of heteroatoms is paramount to import surface active sites. We engineer the deterministic nitrogen atoms inserting the bulk material to preferentially expose active sites to turn the inactive material into a sufficient electrocatalyst. The excellent electrocatalytic activity of N-In 2 O 3 nanocrystals leads to higher performance of dye-sensitized solar cells (DSCs) than the DSCs fabricated with Pt. The successful strategy provides the rational design of transforming abundant materials into high-efficient electrocatalysts. More importantly, the exciting discovery of turning the commonly used transparent conductive oxide (TCO) in DSCs into counter electrode material means that except for decreasing the cost, the device structure and processing techniques of DSCs can be simplified in future. Increasing energy demands have stimulated intense research on electrocatalysts for oxygen reduction reaction, water reduction reaction and triiodide (I 3 2 ) reduction reaction etc, which are at the heart of the typical key renewable-energy technologies such as fuel cells 1,2 , water splitting 3,4 , dye-sensitized solar cells (DSCs) 5,6 and so on. Platinum (Pt) is always the suitable electrocatalyst for these reduction reactions due to its high conductivity, good catalytic activity and chemical stability, but its low abundance ratio and high costs precluded the large-scale utilizations of these renewable-energy technologies. These considerations have led to ongoing efforts to design molecular catalysts that employ earth-abundant materials, to match up to or surpass the catalytic activity of Pt. Because high electric conductivity and good catalytic activity are the two main requirements for an efficient electrocatalyst, screening the alternatives among the abundant conductive materials like conductive oxides is a reasonable way. However, according to our previous theoretical research 7 , some conductive oxides such as indium oxide (In 2 O 3 ), stannic oxide (SnO 2 ) and zinc oxide (ZnO) are unfortunately proven to be electrocatalytically inactive, due to their low adsorption energies of reactant molecules and scarce active sites which are necessary for adsorption of the reactants, bond-breaking and bond-formation, and desorption of the products in the heterogeneous catalytic process 8 . To deliver these intrinsically inactive but abundant materials into active catalysts, one needs to control the atomic-scale surface structure to preferentially expose a greater fraction of the active sites 9 or exhibit a higher adsorption energy, which is highly challenging but desirable. Along the way, recent studies have shown that doping the carbon nanotubes and graphene with heteroatoms or defects sites can...

No abstract