Oxygen-Bridged Indium-Nickel Atomic Pair as Dual-Metal Active Sites Enabling Synergistic Electrocatalytic CO2 Reduction

Single-atom catalysts offer a promising pathway for electrochemical CO₂ conversion. However, it is still a challenge to optimize the electrochemical performance of dual-atom catalysts. Here, an atomic indium-nickel dual-sites catalyst bridged by an axial oxygen atom (O-In-N₆ -Ni moiety) was anchored on nitrogenated carbon (InNi DS/NC). InNi DS/NC exhibits superior CO selectivity with Faradaic efficiency higher than 90 % over a wide potential range from -0.5 to -0.8 V versus reversible hydrogen electrode (vs. RHE). Moreover, an industrial CO partial current density up to 317.2 mA cm^-2 is achieved at -1.0 V vs. RHE in a flow cell. In situ ATR-SEIRAS combined with theory calculations reveal that the synergistic effect of In-Ni dual-sites and O atom bridge not only reduces the reaction barrier for the formation of *COOH, but also retards the undesired hydrogen evolution reaction. This work provides a feasible strategy to construct dual-site catalysts towards energy conversion.

Atomically Dispersed Zn-Pyrrolic-N4 Cathode Catalysts for Hydrogen Fuel Cells

To achieve practical application of fuel cell, it is vital to develop highly efficient and durable Pt-free catalysts. Herein, we prepare atomically dispersed ZnNC catalysts with Zn-Pyrrolic-N₄ moieties and abundant mesoporous structure. The ZnNC-based anion-exchange membrane fuel cell (AEMFC) presents an ultrahigh peak power density of 1.63 and 0.83 W cm^-2 in H₂ -O₂ and H₂ -air (CO₂ -free), and also exhibits long-term stability with more than 120 and 100 h for H₂ -air (CO₂ -free) and H₂ -O₂ , respectively. Density functional calculations further unveil that the Zn-Pyrrolic-N₄ structure is the origin of high activity of as-synthesized ZnNC catalyst, while the Zn-Pyridinic-N₄ moiety is inactive for oxygen reduction reaction (ORR), which successfully explain the puzzle why most Zn-metal-organic framework -derived ZnNC catalysts in previous reports did not present good ORR activity because of their Zn-Pyridinic-N₄ moieties. This work offers a new route for speeding up development of AEMFCs.

Promoting CO2 Electroreduction Kinetics on Atomically Dispersed Monovalent Zn(I) Sites by Rationally Engineering Proton-feeding Centers

Electrocatalytic reduction of CO2 (CO2RR) to value-added chemicals is of great significance for CO2 utilization. Due to the slow proton-feeding rates from sluggish water dissociation kinetics, however, the CO2RR process involving multi-electron and proton transfer is greatly limited by poor selectivity and low yield. Herein, we develop an atomically dispersed monovalent zinc anchored on nitrogenated carbon nanosheets (Zn/NC NSs) as an efficient catalyst for CO2RR. Benefiting from the unique coordination environment and atomic dispersion, the optimized Zn/NC NSs exhibits a superior CO2RR performance, featured by a high current density up to 50 mA cm-2 with an outstanding CO Faradaic efficiency of ～95%. The center Zn(I) atom coordinated with three N atoms and one N atom that bridge over two adjacent graphitic edge (Zn-N3+1) is identified as the catalytically active site by thorough structural characterizations. In-situ attenuated total reflectance infrared absorption spectroscopy results reveal that the twisted Zn-N3+1 structure accelerates the CO2 activation and protonation in the rate-determining step of *CO2 to *COOH on the rationally engineered proton-feeding centers, while theoretical calculations elucidate that atomically dispersed Zn-N3+1 moieties decrease the potential barriers for the intermediate COOH* formation, promoting the proton-coupled CO2RR kinetics and boosting the overall catalytic performance. A rechargeable Zn-CO2 battery based on the Zn/NC NS cathode delivers a maximal power density of 1.8 mW cm-2.