This work demonstrates the molecular engineering of active sites on a graphene scaffold. It was found that the N-doped graphene nanosheets prepared by a hightemperature nitridation procedure represent a novel chemical function of efficiently catalyzing aerobic alcohol oxidation. Among three types of nitrogen species doped into the graphene latticepyridinic N, pyrrolic N, and graphitic N the graphitic sp 2 N species were established to be catalytically active centers for the aerobic oxidation reaction based on good linear correlation with the activity results. Kinetic analysis showed that the N-doped graphene-catalyzed aerobic alcohol oxidation proceeds via a Langmuir−Hinshelwood pathway and has moderate activation energy (56.1 ± 3.5 kJ•mol −1 for the benzyl alcohol oxidation) close to that (51.4 kJ•mol −1 ) proceeding on the catalyst Ru/Al 2 O 3 reported in literature. An adduct mechanism was proposed to be different remarkably from that occurring on the noble metal catalyst. The possible formation of a sp 2 N−O 2 adduct transition state, which can oxidize alcohols directly to aldehydes without any byproduct, including H 2 O 2 and carboxylic acids, may be a key element step. Our results advance graphene chemistry and open a window to study the graphitic sp 2 nitrogen catalysis.

Strong metal-support interaction (SMSI) has gained great attention in the field of heterogeneous catalysis. However, whether single-atom catalysts can exhibit SMSI remains unknown. Here, we demonstrate that SMSI can occur on TiO 2-supported Pt single atoms but at a much higher reduction temperature than that for Pt nanoparticles (NPs). Pt single atoms involved in SMSI are not covered by the TiO 2 support nor do they sink into its subsurface. The suppression of CO adsorption on Pt single atoms stems from coordination saturation (18-electron rule) rather than the physical coverage of Pt atoms by the support. Based on the new finding it is revealed that single atoms are the true active sites in the hydrogenation of 3-nitrostyrene, while Pt NPs barely contribute to the activity since the NP sites are selectively encapsulated. The findings in this work provide a new approach to study the active sites by tuning SMSI.

The electrochemical N 2 fixation to produce ammonia is attractive but significantly challenging with low yield and poor selectivity. Herein, we first used density function theory calculations to reveal adjacent bi-Ti 3+ pairs formed on anatase TiO 2 as the most active electrocatalytic centers for efficient N 2 lying-down chemisorption and activation. Then, by doping of anatase TiO 2 with Zr 4+ that has similar d -electron configuration and oxide structure but relatively larger ionic size, the adjacent bi-Ti 3+ sites were induced and enriched via a strained effect, which in turn enhanced the formation of oxygen vacancies. The Zr 4+ -doped anatase TiO 2 exhibited excellent electrocatalytic N 2 fixation performances, with an ammonia production rate (8.90 µg·h −1 ·cm −2 ) and a Faradaic efficiency of 17.3% at −0.45 V versus reversible hydrogen electrode under ambient aqueous conditions. Moreover, our work suggests a viewpoint to understand and apply the same-valance dopants in heterogeneous catalysis, which is generally useful but still poorly understood.

Electrochemical reduction of carbon monoxide (CO) has recently been emerging as a potential alternative for converting carbon emission into high-value multi-carbon products such as acetate. Nonetheless, the activity and selectivity for producing acetate have remained low. Herein, we developed an atomically ordered copper-palladium intermetallic compound (CuPd-IC) structure that achieved a high Faradaic e ciency of 70 ± 5% for CO-to-acetate production with a partial current density of 425 mA•cm − 2 . This corresponded to an acetate production rate of 4.0 mmol•h − 1 •cm − 2 , and 5.3 times of enhancement in acetate production compared to pure Cu. Structural characterizations and density functional theory calculations suggested that CuPd-IC presents a high density of Cu-Pd pairs that act as the active sites to enrich the surface CO coverage, stabilize the surface ethenone as a key acetate-path intermediate, and inhibit hydrogen evolution reaction, thus promoting acetate formation. Using a membrane electrode assembly device, the CuPd-IC catalyst enabled 100 hours of CO-to-acetate operation at 500 mA•cm − 2 and an average acetate Faradaic e ciency of 43%, producing ~ 2 mol acetate.

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