Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis, but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature. We herein report a surface active-site engineering strategy for constructing the hierarchical PtNi nanocatalysts with an atomic Pt-skin layer (PtNi@Pt-SL) towards efficient triiodide reduction reaction (TRR) via an acid-dealloying approach. The facile acid-dealloying process promotes the formation of surface Pt active sites on the hierarchical Pt-alloys, and thus results in good catalytic performance towards TRR. Theoretical calculation reveals that the enhanced catalytic property stems from the moderate energy barriers for iodide atoms on the surface Pt active-sites. The surface active-site engineering strategy paves a new way for the design of active and durable electrocatalysts.

Photocathode with superior catalytic activity, long-term stability, and fast mass/electron transfer is highly desirable but challenging for dye-sensitized solar cell (DSC). Herein, the ZIF-67 grown on carbon cloth is successfully transformed into CoSe₂ embedded in N-doped carbon nanocage (CoSe₂/N-C) via a growth-carbonization-selenization process. The carbon cloth supported CoSe₂/N-C, as photocathode of DSC, demonstrates a good long-term stability and high photovoltaic efficiency (8.40%), outperforming Pt. The good efficiency can be attributed to the high catalytic activity of CoSe₂, fast mass transfer of porous three-dimensional (3D) structure, and good electron transport derived from the intimate contact between CoSe₂ and highly conductive carbon cloth. The high stability would be ascribed to N-doped carbon coating that perfectly prevents CoSe₂ from decomposition. This work will pave the way to develop highly efficient and stable Pt-free photocathode for DSC.