Facile synthesis of channel-rich ultrathin palladium-silver nanosheets for highly efficient formic acid electrooxidation

Abstract

The rational design and synthesis of two-dimensional (2D) materials with specific composition, morphology, and surface atomic structure is of great importance for the practical applications in electrocatalysis. Herein, we report a facile synthesis of channel-rich ultrathin palladium-silver nanosheets (PdAg NSs) by a simple wet-chemical strategy based on the self-assembly of docosyltrimethylammonium chloride (C22TAC). The nanosheets consist of 2D ultrathin nanosheets with many accessible channels and alloyed crystalline feature. The formation mechanism of PdAg NSs is systematically investigated via a series of control experiments, including reaction time, surfactant, Pd/Ag molar ratio, temperature, and reducing agent. It is demonstrated that C22TAC molecule with long alkyl chain and interplay between constituent metals is crucial for the anisotropic growth of 2D nanosheets. Such C22TAC-based synthetic strategy can also be extended to the synthesis of PdAg nanowires (PdAg NWs) and Pd mesoporous nanobowls (Pd NBs). Benefit from composition and structure advantages, the obtained PdAg NSs exhibit superior electrocatalytic performance toward formic acid oxidation reaction (FAOR) with mass activity of 987 mA mg−1 and specific activity of 50.1 A m−2 at 0.3 V, which are better than those of PdAg NWs and Pd NBs, even surpass commercial Pd black. We believe the synthetic strategy outlined here would open a new avenue for engineering of noble-metal nanocrystals for a broad range of applications.