CO2 hydrogenation to hydrocarbons over heterogeneous catalysts.

Efficient electroreduction of CO 2 to multi-carbon products is a challenging reaction because of the high energy barriers for CO 2 activation and CC coupling, which can be tuned by designing the metal centers and coordination environments of catalysts. Here, we design single atom copper encapsulated on N-doped porous carbon (Cu-SA/NPC) catalysts for reducing CO 2 to multi-carbon products. Acetone is identified as the major product with a Faradaic efficiency of 36.7% and a production rate of 336.1 μg h −1. Density functional theory (DFT) calculations reveal that the coordination of Cu with four pyrrole-N atoms is the main active site and reduces the reaction free energies required for CO 2 activation and CC coupling. The energetically favorable pathways for CH 3 COCH 3 production from CO 2 reduction are proposed and the origin of selective acetone formation on Cu-SA/NPC is clarified. This work provides insight into the rational design of efficient electrocatalysts for reducing CO 2 to multi-carbon products.

Density functional theory (DFT) calculations on Pd-Cu bimetallic catalysts reveal that the stepped PdCu(111) surface with coordinatively unsaturated Pd atoms exposed on the top is superior for CO 2 and H 2 activation and for CO 2 hydrogenation to methanol in comparison to the flat Cu-rich PdCu 3 (111) surface. The energetically preferred path for CO 2 to CH 3 OH over PdCu(111) proceeds through CO 2 * → HCOO* → HCOOH* → H 2 COOH* → CH 2 O* → CH 3 O* → CH 3 OH*. CO formation from CO 2 via a reverse water-gas shift (RWGS) proceeds more quickly than CH 3 OH formation in terms of kinetic calculations, in line with experimental observation. A small amount of water, which is produced in situ from both RWGS and CH 3 OH formation, can accelerate CO 2 conversion to methanol by reducing the kinetic barriers for O−H bond formation steps and enhancing the TOF. Water participation in the reaction alters the rate-limiting step according to the degree of rate control (DRC) analysis. In comparison to CO 2 , CO hydrogenation to methanol on PdCu(111) encounters higher barriers and thus is slower in kinetics. Complementary to the DFT results, CO 2 hydrogenation experiments over SiO 2 -supported bimetallic catalysts show that the Pd-Cu(0.50) that is rich in a PdCu alloy phase is more selective to methanol than the PdCu 3 -rich Pd-Cu(0.25). Moreover, advanced CH 3 OH selectivity is also evidenced on Pd-Cu(0.50) at a specific water vapor concentration (0.03 mol %), whereas that of Pd-Cu(0.25) is not comparable. The present work clearly shows that the PdCu alloy surface structure has a major effect on the reaction pathway, and the presence of water can substantially influence the kinetics in CO 2 hydrogenation to methanol.

Photoreduction of CO 2 to C 2 + solar fuel is a promising carbon-neutral technology for renewable energy. This strategy is challenged by its low productivity due to low efficiency in multielectron utilization and slow CÀ C coupling kinetics. This work reports a dualmetal photocatalyst consisting of atomically dispersed indium and copper anchored on polymeric carbon nitride (InCu/PCN), on which the photoreduction of CO 2 delivered an excellent ethanol production rate of 28.5 μmol g À 1 h À 1 with a high selectivity of 92 %. Coupled experimental investigation and DFT calculations reveal the following mechanisms underpinning the high performance of this catalyst. Essentially, the InÀ Cu interaction enhances the charge separation by accelerating charge transfer from PCN to the metal sites. Indium also transfers electrons to neighboring copper via CuÀ NÀ In bridges, increasing the electron density of copper active sites. Furthermore, InÀ Cu dual-metal sites promote the adsorption of *CO intermediates and lower the energy barrier of CÀ C coupling.