The rational design of highly efficient, low-cost, and durable electrocatalysts to replace platinum-based electrodes for oxygen reduction reaction (ORR) is highly desirable. Although atomically dispersed supported metal catalysts often exhibit excellent catalytic performance with maximized atom efficiency, the fabrication of single-atom catalysts remains a great challenge because of their easy aggregation. Herein, a simple ionothermal method was developed to fabricate atomically dispersed Fe−N x species on porous porphyrinic triazine-based frameworks (FeSAs/PTF) with high Fe loading up to 8.3 wt %, resulting in highly reactive and stable single-atom ORR catalysts for the first time. Owing to the high density of single-atom Fe−N 4 active sites, highly hierarchical porosity, and good conductivity, the as-prepared catalyst FeSAs/PTF-600 exhibited highly efficient activity, methanol tolerance, and superstability for oxygen reduction reaction (ORR) under both alkaline and acidic conditions. This work will bring new inspiration to the design of highly efficient noble-metal-free catalysts at the atomic scale for energy conversion.

Paired electrosynthesis is a promising technology with the potential to generate value-added products at both electrodes in a cost-effective manner. Herein, 3D vanadium nitride (VN) and Pd/VN hollow nanospheres are successfully fabricated and coupled to carry out simultaneous electrocatalytic oxidation (ECO) and electrocatalytic hydrogenation (ECH) of 5-hydroxymethylfurfural (HMF) into 2, 5-furandicarboxylic acid (FDCA) and 2,5-bishydroxymethyl-tetrahydrofuran (DHMTHF), respectively. VN shows excellent ECO performance with high HMF conversion (≥98%), FDCA selectivity (≥96%), and faradaic efficiency (≥84%) after a stability test, and Pd/VN achieves high ECH selectivity for DHMTHF at ≥88% and an HMF conversion of ≥90%, with a faradaic efficiency of ≥86%. VN and Pd/VN incorporated into a membrane electrode assembly in a paired electrolysis system shows potential for large-scale biomass conversion and upgrading. Theoretical calculations reveal that the higher performance of VN for the production of ECO can be attributed to its lower d-band center level relative to the Fermi level compared to that of V 2 O 5 , which favors HMF chemisorption and activation. This study paves the way for developing paired electrosynthesis technologies with the potential for biomass utilization and energy conversion.

Cobalt single atoms anchored on porphyrinic triazine frameworks exhibit high activity in ORR and HER.

Electroreduction of CO 2 (CO 2 RR) to value-added chemicals offers a promising approach to balance the global carbon emission, but still remains a significant challenge due to high overpotential, low faradaic efficiency, and poor selectivity of electrocatalysts systems. Thus the key point is to develop low-cost, highly efficient, and durable electrocatalysts for CO 2 RR. To benefit from their exposed active sites and to maximize atomic efficiency, single-metal atom catalysts that usually show high activities are required. Herein, we unravel the trends in the reactivity and selectivity of atomically isolated M-N 4 (M = Ni, Cu, Fe, and Co) sites within porous porphyrinic triazine framework (metal single atoms/PTF) for the electroreduction of CO 2 to CO. We found that NiSAs/PTF exhibited the highest faradaic efficiency (98%) at a mild potential of −0.8 V versus reversible hydrogen electrode and the highest turnover frequency of 13,462 h −1 for the production CO at an applied potential of −1.2 V. The relations of catalytic performance of CO 2 to CO over the different active M-N 4 sites were unraveled by the combination of density functional theory calculations and experiments. This work gives an extensive mechanistic understanding of the selectivity of CO 2 to CO from the M-N 4 sites at an atomic scale, thus it will bring new inspiration for the design of highly efficient CO 2 RR.