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Direct Observation for Dynamic Bond Evolution in Single-Atom Pt/C3N4 Catalysts.

Single-atom catalyst emerges as a highly promising platform for heterogeneous catalysis, especially in the applications of clean energy conversion, storage and utilization. To understand the associated mechanisms, great efforts have been made to examine the bonding and oxidation state of single-atom catalysts before and/or after catalytic reactions; however, such assignments without sufficient information for dynamic evolution often lead to overlooking the underlying mechanisms. In this work, we report the first direct observation for the charge transfer and bond evolution of single-atom Pt/C 3 N 4 catalyst in photocatalytic water splitting using synchronous illumination X-ray photoelectron spectroscopy (SI-XPS). Specifically under light excitation, we observe the Pt-N bond cleavage to form Pt 0 species and the corresponding C=N bond reconstruction for the first time, while these features could not be detected on the metallic Pt decorated C 3 N 4 catalyst. As expected, a significant enhancement of H 2 production activity (14.7 mmol·h -1 ·g -1 ) is achieved on single-atom Pt/C 3 N 4 catalyst, 20 times higher than that of metallic Pt-C 3 N 4 (0.74 mmol·h -1 ·g -1 ). These findings bring new insights for depth understanding of single-atom catalysts during catalytic reactions at the atomic level.