Size effect has been regularly utilized to tune the catalytic activity and selectivity of metal nanoparticles (NPs). Yet, there is a lack of understanding of the size effect in the electrocatalytic reduction of CO2, an important reaction that couples with intermittent renewable energy storage and carbon cycle utilization. We report here a prominent size-dependent activity/selectivity in the electrocatalytic reduction of CO2 over differently sized Pd NPs, ranging from 2.4 to 10.3 nm. The Faradaic efficiency for CO production varies from 5.8% at -0.89 V (vs reversible hydrogen electrode) over 10.3 nm NPs to 91.2% over 3.7 nm NPs, along with an 18.4-fold increase in current density. Based on the Gibbs free energy diagrams from density functional theory calculations, the adsorption of CO2 and the formation of key reaction intermediate COOH* are much easier on edge and corner sites than on terrace sites of Pd NPs. In contrast, the formation of H* for competitive hydrogen evolution reaction is similar on all three sites. A volcano-like curve of the turnover frequency for CO production within the size range suggests that CO2 adsorption, COOH* formation, and CO* removal during CO2 reduction can be tuned by varying the size of Pd NPs due to the changing ratio of corner, edge, and terrace sites.

Novel non-precious-metal catalysts encapsulated in N-doped carbon nanotubes exhibit high activity and remarkable stability towards hydrogen evolution reaction (HER) in acidic medium.

Coordinatively unsaturated Ni–N active sites facilitate CO2electroreduction and inhibit the competitive hydrogen evolution reaction, demonstrating selective and high-rate CO2electroreduction.

A coordinatively unsaturated single iron site confined in a graphene matrix shows an ultrahigh activity for catalytic oxidation.

CeO takes charge: Ceria grows forming small islands on terraces (2–5 nm, CeOx‐I) and large islands on steps of a copper substrate (30–50 nm, CeOx‐II; see scheme; 100×100 nm2). The resulting CeOx/Cu(111) systems display an extraordinary water‐gas shift activity and illustrate the role that an oxide can play in improving the performance of copper‐based catalysts.

The electrochemical CO reduction reaction (CORR) typically uses transition metals as the catalysts. To improve the efficiency, tremendous efforts have been dedicated to tuning the morphology, size, and structure of metal catalysts and employing electrolytes that enhance the adsorption of CO. We report here a strategy to enhance CORR by constructing the metal-oxide interface. We demonstrate that Au-CeO shows much higher activity and Faradaic efficiency than Au or CeO alone for CORR. In situ scanning tunneling microscopy and synchrotron-radiation photoemission spectroscopy show that the Au-CeO interface is dominant in enhancing CO adsorption and activation, which can be further promoted by the presence of hydroxyl groups. Density functional theory calculations indicate that the Au-CeO interface is the active site for CO activation and the reduction to CO, where the synergy between Au and CeO promotes the stability of key carboxyl intermediate (*COOH) and thus facilitates CORR. Similar interface-enhanced CORR is further observed on Ag-CeO, demonstrating the generality of the strategy for enhancing CORR.

Graphene-confined single Fe atoms, screened out from a series of 3d transition metals (Mn, Fe, Co, Ni, and Cu), were used as an efficient non-precious catalyst to directly convert methane to C1 oxygenated products at room temperature. The unique O-FeN 4 -O structure formed in graphene can readily activate the C-H bond of methane along a radical pathway with a low reaction energy barrier.

A Cu(111) surface displays a low activity for the oxidation of carbon monoxide (2CO + O(2) → 2CO(2)). Depending on the temperature, background pressure of O(2), and the exposure time, one can get chemisorbed O on Cu(111) or a layer of Cu(2)O that may be deficient in oxygen. The addition of ceria nanoparticles (NPs) to Cu(111) substantially enhances interactions with the O(2) molecule and facilitates the oxidation of the copper substrate. In images of scanning tunneling microscopy, ceria NPs exhibit two overlapping honeycomb-type moiré structures, with the larger ones (H(1)) having a periodicity of 4.2 nm and the smaller ones (H(2)) having a periodicity of 1.20 nm. After annealing CeO(2)/Cu(111) in O(2) at elevated temperatures (600-700 K), a new phase of a Cu(2)O(1+x) surface oxide appears and propagates from the ceria NPs. The ceria is not only active for O(2) dissociation, but provides a much faster channel for oxidation than the step edges of Cu(111). Exposure to CO at 550-750 K led to a partial reduction of the ceria NPs and the removal of the copper oxide layer. The CeO(x)/Cu(111) systems have activities for the 2CO + O(2) → 2CO(2) reaction that are comparable or larger than those reported for surfaces of expensive noble metals such as Rh(111), Pd(110), and Pt(100). Density-functional calculations show that the supported ceria NPs are able to catalyze the oxidation of CO due to their special electronic and chemical properties. The configuration of the inverse oxide/metal catalyst opens new interesting routes for applications in catalysis.