A facile and scalable synthesis of N₄Fe–CuN₃ diatomic sites on N-doped carbon frameworks. The CO Faraday efficiency is >95% at −0.4 to −1.1 V with an overpotential of 50 mV.

Polybenzimidazole (PBI) membranes with nanophase-separated structure induced by non-ionic hydrophilic side chain are designed and fabricated for vanadium flow batteries (VFBs). The designed PBI membranes are prepared by grafting non-ionic hydrophilic side chains via an N-substitution reaction. This molecular modification induces nanophase separation and formation of hydrophilic clusters, which act as effective proton transfer pathways, hence dramatically improving the proton conductivity. Meanwhile, the vanadium permeability is inappreciable due to the appropriate size of hydrophilic clusters and Donnan exclusion of protonated grafted-PBI membranes (GPBI). Free from ion exchange groups, GPBI membranes maintain the good chemical stability of the pristine PBI membrane. As a result, the designed membrane exhibits an impressive performance, combining ultrahigh proton conductivity, ion selectivity and chemical stability. The GPBI-based VFB exhibits a coulombic efficiency of over 99% and an energy efficiency of 84% at 120 mA cm⁻², the highest reported for dense PBI membranes for VFB applications. The decent stability of GPBI membranes is demonstrated by the stable performance over 200 charge–discharge cycles and the ex situ immersion test. This work provides a new insight into the design of high-performance PBI membranes for VFB applications.

Alkali metal anodes (Li, Na, K) are highly promising for enabling high-energy-density rechargeable batteries due to their high theoretical capacities and low redox potentials. Although extensive studies have been performed on Li-metal, dendrite growth and serious interface issues are still fundamental challenges for practical alkali metal batteries (AMBs). Here, we report an in situ-formed graphite intercalation compound (GIC) framework that enables Na–K liquid alloy to be used in ultra-stable and high-capacity anodes, attributed to the synergy of fast electron and mass transport of the GIC networks associated with the self-healing behavior of the Na–K alloy. The Na–K composite electrode is highly stable; it sustains repeated stripping/deposition over 5000 hours at 20 mA cm⁻² and achieves stable electrodeposition even at 80 mA cm⁻² and 16 mA h cm⁻². When coupled with various cathodes, versatile AMBs are realized with long cycling and high operating voltages. This framework electrode design presents new insight into developing dendrite-free alkali metal anodes.