Exploring the N Adsorption and Activation Mechanisms over the 2H/1T Mixed-Phase Ultrathin MoWS Nanosheets for Boosting N Photosynthesis.

Solar-driven conversion of nitrogen (N) to ammonia (NH) is highly appealing, yet in its infancy, the low photocatalytic efficiency and unclear adsorption and activation mechanisms of N are still issues to be addressed. In this study, ultrathin alloyed MoWS nanosheets with tunable hexagonal (2H)/trigonal (1T) phase ratios were proposed to boost photoreduction N efficiency, while the mechanisms of N adsorption and activation were explored simultaneously. The alloyed MoWS nanosheets for the 1T phase concentration of 33.6% and Mo/W = 0.68:0.32 were proven to reach about 111 μmol g h under visible light, which is 3.7 (or 3)-fold higher than that of pristine MoS (or WS). With the aid of density functional theory calculations and N adsorption X-ray absorption near-edge fine structure techniques, the adsorption and activation behaviors of N over the interface of MoWS nanosheets were investigated during the N reduction process. The results show that the W doping causes a higher electron density state in W 5d orbitals, which can further polarize the adsorbed N molecules for adsorption and activation. This work provides a new insight into the adsorption and activation mechanisms for the NH synthesis.