  Understanding the mechanism and developing strategies toward efficient
electrocatalysis at gas-liquidsolid interfaces are important yet challenging.
In the past decades, researchers have devoted many efforts to improving
catalyst activity by modulating electronic properties of catalysts in terms of
chemical components and physical features. Here we develop a mosaic catalyst
strategy to improve activity of electrocatalysts by engineering their spatial
structures. Taking Pt catalyst as an example, the mosaic Pt leads to high
catalytic performance, showing a specific activity 11 times higher than uniform
Pt films for hydrogen evolution reaction (HER), as well as higher current
densities than commercial Pt/C and uniform Pt films. Such a strategy is found
to be general to other catalysts (e.g., twodimensional PtS) and other reactions
(e.g., oxygen evolution reaction). The improved catalytic performance of the
mosaic catalysts is attributed to enhanced mass transferability and local
electric field, both are determined by the occupation ratio of catalysts. Our
work shines new light on manipulating electrocatalysis from the perspective of
the spatial structure of catalyst, which would guide the design of efficient
catalysts for heterogeneous reactions.
