Constructing high-accessibility Fe single-atoms via directional anchoring strategy for boosting electrochemical sensing

The regulation of the activity of single-atom nanozymes is crucial for the development of highly sensitive electrochemical sensors. The accessibility of single-atom nanozymes is an important factor limiting their activity. This study proposes a directional anchoring strategy to regulate the accessibility of single-atom nanozymes for boosting electrochemical nonenzymatic H 2 O 2 sensing. The directional anchoring of Fe single-atoms on the inner surface of nitrogen-doped carbon materials (In-Fe SAs/NC) and the outer surface of nitrogen-doped carbon materials (Out-Fe SAs/NC) was achieved via the hard template assisted method. The impact of the anchoring position of Fe SAs on the electrocatalytic reduction of H 2 O 2 was investigated. Density functional theory (DFT) calculations reveal that Fe SAs nanozymes are more likely to activate H 2 O 2 than the previously reported Fe 3 O 4 nanozymes. The anchoring of Fe SAs on the outer surface of NCs markedly enhances the accessibility of active sites in comparison to anchoring Fe SAs on the inner surface, thereby increasing the sensitivity for the detection of H 2 O 2 . The electrochemical sensor based on Out-Fe SAs/NC can be used to detect H 2 O 2 content in milk samples. The high accessibility and excellent intrinsic activity of Fe SAs render Out-Fe SAs/NC a highly effective sensing material.