Photoinduced H2 Heterolysis to Form Mo2NHx Active Species for CO2 Reduction

Developing low-cost catalytic materials to utilize both solar and thermal energy and uncovering the active species are highly desirable for efficient selective reduction of CO2 to CO (SRCC) through the reverse water–gas shift reaction. Here, molybdenum nitride (Mo2N) was demonstrated as an efficient photoassisted catalyst for SRCC at low temperature (175 °C; 1.0 W·cm–2 UV–vis light; CO yield rate, 0.35 mmol·g–1·h–1). The CO yield rate was 26.7 times higher than that in the absence of light illumination. The greatly improved yield was ascribed to the formation of highly active species Mo2NHx via the photoinduced H2 heterolysis. Besides, the photoinduced broken-symmetry of atomic electron densities in Mo–N pairs might strengthen the local electric fields and thus caused H2 heterolysis to form Mo2NHx active species at low temperature. Moreover, the appearance of Mo2NHx could lower the activation barriers, leading to an improved CO yield. Furthermore, the reversible transformation between Mo2N and Mo2NHx endowed Mo2N with high durability for SRCC.