A robust MoS2 catalyst engineered via two-step K modification strategy for the high‑temperature reverse water‑gas shift reaction

The catalytic conversion of CO 2 to CO via the reverse water–gas shift (RWGS) reaction represents a promising strategy for mitigating carbon emissions. The key challenge lies in designing catalysts that simultaneously achieve high activity, selectivity, and long-term stability. The use of elevated temperatures to boost CO 2 conversion often comes at the expense of CO selectivity and catalyst durability. To address this, few-layer MoS 2 rich in sulfur vacancies (S v ) was synthesized via a hydrothermal method and subsequently modified by KOH washing and KNO 3 impregnation for the RWGS reaction. K introduction effectively suppressed the formation of CH 4 and methanol, thereby enhancing CO selectivity. The optimal catalyst (K/Mo = 0.72) exhibited the lowest apparent activation energy (41.54 kJ/mol). Under demanding conditions (450 °C, 4 MPa, 120,000 mL g -1 h −1 ), it maintained stable performance for 500 h, with CO 2 conversion exceeding 41 % and CO selectivity above 95 %, achieving a CO space‑time yield (STY) of 14.61 g CO gcat -1 h −1 . Characterization revealed that KNO 3 impregnation induced partial oxidation of MoS 2 during calcination, generating MoO 2 and K 2 SO 4 phases. These phases acted as structural promoters, stabilizing the active sites and enhancing catalyst robustness. Moreover, K modification strengthened CO 2 adsorption and facilitated CO desorption. Combined in situ DRIFTS and DFT indicated that K-modified S v sites on MoS 2 basal planes favor the COOH* decomposition pathway. In contrast, unmodified MoS 2 -0 predominantly follow the HCOO* hydrogenation route, leading to deep hydrogenation and CH 4 formation.