Hydrogen-Bonded Organic Framework Supporting Atomic Bi-N2O2 Sites for High-Efficiency Electrocatalytic CO2 Reduction.

Single atomic catalysts (SACs) offer a superior platform for studying the structure-activity relationships during electrocatalytic CO2 reduction reaction (CO2RR). Yet challenges still exist to obtain well-defined and novel site configuration owing to the uncertainty of functional framework-derived SACs through calcination. Herein, a novel Bi-N2O2 site supported on the (1 1 0) plane of hydrogen-bonded organic framework (HOF) is reported directly for CO2RR. In flow cell, the target catalyst Bi1-HOF maintains a faradaic efficiency (FE) HCOOH of over 90 % at a wide potential window of 1.4 V. The corresponding partial current density ranges from 113.3 to 747.0 mA cm-2. And, Bi1-HOF exhibits a long-term stability of over 30 h under a successive potential-step test with a current density of 100-400 mA cm-2. Density function theory (DFT) calculations illustrate that the novel Bi-N2O2 site supported on the (1 1 0) plane of HOF effectively induces the oriented electron transfer from Bi center to CO2 molecule, reaching an enhanced CO2 activation and reduction. Besides, this study offers a versatile method to reach series of M-N2O2 sites with regulable metal centers via the same intercalation mechanism, broadening the platform for studying the structure-activity relationships during CO2RR.

Enhanced Metal-Support Interactions Boost the Electrocatalytic Water Splitting of Supported Ruthenium Nanoparticles on a Ni3 N/NiO Heterojunction at Industrial Current Density.

Developing highly efficient and stable hydrogen production catalysts for electrochemical water splitting (EWS) at industrial current densities remains a great challenge. Herein, we proposed a heterostructure-induced-strategy to optimize the metal-support interaction (MSI) and the EWS activity of Ru-Ni3 N/NiO. Density functional theory (DFT) calculations firstly predicted that the Ni3 N/NiO-heterostructures can improve the structural stability, electronic distributions, and orbital coupling of Ru-Ni3 N/NiO compared to Ru-Ni3 N and Ru-NiO, which accordingly decreases energy barriers and increases the electroactivity for EWS. As a proof-of-concept, the Ru-Ni3 N/NiO catalyst with a 2D Ni3 N/NiO-heterostructures nanosheet array, uniformly dispersed Ru nanoparticles, and strong MSI, was successfully constructed in the experiment, which exhibited excellent HER and OER activity with overpotentials of 190 mV and 385 mV at 1000 mA cm-2 , respectively. Furthermore, the Ru-Ni3 N/NiO-based EWS device can realize an industrial current density (1000 mA cm-2 ) at 1.74 V and 1.80 V under alkaline pure water and seawater conditions, respectively. Additionally, it also achieves a high durability of 1000 h (@ 500 mA cm-2 ) in alkaline pure water.

Tuning the Spin State of the Iron Center by Bridge-Bonded Fe-O-Ti Ligands for Enhanced Oxygen Reduction.

Exploring functional substrates and precisely regulating the electronic structures of atomic metal active species with moderate spin state are of great importance yet remain challenging. Hereon, we provide an axial Fe-O-Ti ligand regulated spin-state transition strategy to improve the oxygen reduction reaction (ORR) activity of Fe centers. Theoretical calculations indicate that Fe-O-Ti ligands in FeN3 O-O-Ti can induce a low-to-medium spin-state transition and optimize O2 adsorption by FeN3 O. As a proof-of-concept, the oriented catalyst was prepared from atomic-Fe-doped polymer-like quantum dots and ultrathin o-terminated MXene. The optimal catalyst exhibits an intrinsic activity that is almost 5 times higher than the control sample (without axial Fe-O-Ti ligands). It also delivers a superior performance in Zn-air batteries and H2 /O2 anion exchange membrane fuel cells in a wide-temperature range.