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Abstract With intriguing physiochemical properties and widespread promising applications, ultrathin nanosheets (NSs) with only atomic thickness have drawn increasing attention. The ultrathin Pd, Pd‐based alloy and intermetallic perforated nanosheets (PNSs) have been extensively studied in fuel cells (FCs)‐related reactions, including the cathodic oxygen reduction reaction (ORR) and anodic methanol, ethanol, and formic acid oxidation reactions (MOR, EOR, and FAOR). In this review, we briefly summarize the preparation of ultrathin Pd, Pd‐based alloy and intermetallic PNSs, as well as their advantages in electrocatalytic applications including ORR, MOR, EOR, and FAOR. Finally, the major challenges and perspectives for future development of ultrathin Pd, Pd‐based alloy and intermetallic PNSs electrocatalysts are proposed to accelerate the commercialization of future promising FCs.

Abstract In this paper, the gas‐sensing properties of copper oxide porous nanosheets in amorphous and highly crystalline states were comparatively investigated on the premise of almost the same specific surface area, morphology and size. Unexpectedly, the results show that amorphous copper oxide porous nanosheets have much better gas sensing properties than highly crystalline copper oxide to a serious of volatile organic compounds, and the lowest detection limit (LOD) of the amorphous copper oxide porous nanosheets to methanal is even up to 10 ppb. By contrast, the LOD of the highly crystalline copper oxide porous nanosheets to methanal is 95 ppb. Experiments prove that the oxygen vacancies contained in the amorphous copper oxide porous nanosheets play a key role in improving gas sensitivity, which greatly improve the chemical activity of the materials, especially for the adsorption of molecules containing oxygen‐groups such as methanal and oxygen.