Vapor-phase hydrothermal construction of defective MoS2 for highly selective electrocatalytic hydrogenation of cinnamaldehyde

Abstract

Electrocatalytic selective hydrogenation of α,β-unsaturated aldehydes with water as the hydrogen donor is of great significance to produce fine chemicals. Here, we propose a facile vapor-phase hydrothermal (VPH) method to directly grow defective MoS₂ nanoparticles on commercial carbon fiber cloth (MoS₂/CFC) for electrocatalytic selective hydrogenation of cinnamaldehyde (CAL). The as-prepared MoS₂/CFC exhibited the highest CAL conversion of 88.8% with a maximum TOF value of 12.8 mmol mmol_MoS2⁻¹ h⁻¹ at −0.7 V vs. RHE. The high selectivity of CAL hydrogenation could be realized by adjusting the applied potentials, CO hydrogenation product cinnamyl alcohol (COL) was easier to form under lower applied potentials, whereas CC hydrogenation product hydrocinnamaldehyde (HCAL) was easier to achieve under higher applied potentials. Density functional theory (DFT) calculation findings demonstrated that the Mo vacancies in the defective MoS₂/CFC facilitated the adsorption of hydrogen atoms, which benefited the generation of H_ads and the proceeding of electrocatalytic hydrogenation. Additionally, the existence of Mo vacancies made the CO group more active than the CC group, and reduced the reaction energy of CAL hydrogenation toward COL. Combined with the experimental results and calculation data, we speculate that the real catalytic active center of the defective MoS₂/CFC is the defective configuration of Mo vacancies. Furthermore, the high conversion and selectivity of furfural and benzaldehyde hydrogenation confirmed the universality of the defective MoS₂/CFC catalyst in electrocatalytic hydrogenation reduction of unsaturated and saturated aldehydes.