Rhodium (Rh)-based catalysts hold considerable promise for the direct hydrogenation of CO2 to ethanol (EtOH). However, their catalytic performance is often limited by high selectivity toward C1 products such as CO and CH4, a tendency largely governed by the adsorption strength of CO on Rh sites. Moderate CO interaction is hypothesized to favor the formation of lower alcohols (such as methanol and ethanol). In this work, we developed a phosphorus (P)-doped Rh/TiO2 catalyst that synergistically modulates the electronic structure of Rh and the metal−support interaction. This P-doping strategy is conducive to enhancing methanol and ethanol synthesis, particularly achieving an ethanol production rate of 1.14 gEtOH gRh−1 h−1. Moreover, the P-doped Rh/TiO2 catalyst exhibits a stable performance over 45 h on stream. Comprehensive characterizations including HAADF-STEM, XANES, XPS, and CO-DRIFTS reveal that P doping induces electron transfer from Rh to P, forming Rh2P structures that stabilize an optimized Rh+/Rh0 ratio (∼1:1) under reaction conditions. This electronic modulation weakens CO hydrogenation and promotes C−C coupling. Additionally, P doping could possibly inhibit Rh sintering and preserves the Rh2P phase, enhancing catalytic stability. In situ DRIFTS further confirmed that P doping suppresses CO hydrogenation, thereby inhibiting CH4 formation while promoting methanol and ethanol production. This work demonstrates that P-induced electronic and structural modifications offer an effective strategy for tuning CO2 hydrogenation selectivity toward lower alcohols including methanol and ethanol.
Zhang et al. (Mon,) studied this question.