Search

The urgent demand for terawatt-scale clean energy necessitates the rational design of noble metal catalysts with minimal noble metal loading while maintaining high catalytic activity. However, the durability of low-loading catalysts is a critical concern for their successful industrial implementation. Here, we present a capping strategy using an amorphous HfO2 (m-HfO2) to address this issue. Take Pt/C catalysts with Pt loading as low as 81.39 ng cm−2 as an example, we demonstrate that the m-HfO2 layer (10 nm) serves as an efficient mass transport channel for underneath Pt active sites, and effectively mitigates bubble-induced blockage of active sites by separating bubble formation sites with Pt active sites. Thus, the resulting catalyst exhibits a remarkable mass activity of 122.87 A mg−1 and an overpotential of 11 mV at 10 mA cm−2. Furthermore, the m-HfO2 plays a crucial role in eliminating the structural transformation and extending the lifetime of Pt-based catalysts, as evidenced by no loss of specific activity after consecutively cycling the catalyst for over 100 h. Such a capping strategy is potentially applied to other types of reactions and catalyst systems.

To improve the utilization efficiency of noble metals as well as lower their mass loading in electrocatalysis, the research community has contributed significant efforts to nanostructure noble metal catalysts in various dimensions during recent decades, such as porous structures (3D), nanosheets (2D), nanowires (1D), nanoclusters (0D), and individual atoms (i.e., single-atom catalyst). Recently, with the development of the well-controlled synthesis of atom-thin materials (e.g., the noble metal layer or two-dimensional materials), a new type of catalyst defined as the single-atom-layer catalyst, has emerged, allowing nearly all the atoms at the monolayer to be accessible to catalytic reactions. In this perspective, we first introduced the unique properties of this catalyst and distinguished it from current single-atom catalysts, then highlighted its recent theoretical and experimental progress, and finally discussed critical challenges toward catalytic applications.