Catalysts assumed that properly designed bimetallic systems would provide superior catalytic performance due to the cooperative effects between two atoms. Dual single-atom catalyst (DSAC) PdN 4 /CuN 4 is synthesized using a simple, cost-effective, and efficient electrochemical reduction method. The palladium single-atom is prepared first by electrochemical reduction of copper phthalocyanine to create defective N 4 sites. The new structural feature is characterized by copper reduction from Cu-N 4 coordination and the formation of defected N 4 (▫ M -N 4 ) sites, which react with a Pd precursor and form PdN 4 on the host surface. The DSAC PdN 4 /CuN 4 technique synergistically improves electrocatalytic performance toward the ethylene glycol oxidation reaction. It possesses excellent glycolate selectivity (above 88%) in an alkaline solution with an onset oxidation potential as low as 0.6 V versus a reversible hydrogen electrode, compared to commercial Pd/C. The DSAC electrocatalyst is characterized by its high current density of 83.92 mA cm −2 and high faradic efficiency value (>80%) for glycolate at 1.0 V RHE . The findings suggest a promising method to synthesize the DSACs in varying transition metals to achieve highly efficient, selective, and environmentally friendly catalysts for different applications.

Solid‐state batteries (SSBs) with a Li7La3Zr2O12 (LLZO) garnet electrolyte are attracting much attention as robust and safe alternative to conventional lithium‐ion batteries. Technical challenges in the practical implementation of garnet SSBs are related to the need for high‐temperature sintering, which often leads to undesirable chemical reactions with the cathode material. While these reactions are well understood for composite cathodes, very little is known about similar processes between cathode and separator during battery fabrication. This work focuses on understanding the processes between the composite LiCoO2‐LLZO cathode and the LLZO separator and how they affect the battery performance. The extensive diffusion of Co‐ions within LLZO, which leads to the often‐observed LLZO darkening, is shown to have a significant impact on ionic conductivity, electronic conductivity, and dendrite stability of the separator. Experimental data coupled with large‐scale molecular dynamics simulations uncover the diffusion mechanism for Co‐ions and identify secondary phases that form during these interactions. In addition to extensive Co‐ion diffusion within the grains, a non‐uniform segregation of Co‐ions at grain boundaries is found leading to the formation of three distinct Co‐containing phases. This work offers a general approach to studying the fundamental ion diffusion processes that occur during the fabrication of oxide SSBs.

Anode-free lithium–sulfur batteries (AFLSBs) show a surprisingly prolonged cycle life 2-fold higher than anode-free lithium metal batteries. The principal difference is the presence of an intrinsic polysulfide (PS) shuttle between electrodes in AFLSBs. However, the underlying mechanism for the impact of PS redox species on the electrochemical performance of AFLSBs is not clearly understood. Herein, we investigate the role of PS redox species in retrieving inactive lithium for compensating lithium inventory loss using titration gas chromatography, thereby quantifying inactive lithium accumulated after several cycles. Moreover, XPS analysis reveals reduced lithium sulfide (Li2S/Li2S2) species formed through PS redox shuttle refresh inactive solid electrolyte interface (SEI) composition and stabilize the consecutive cycle lithium deposition. Interestingly, synchrotron-based operando transmission X-ray microscopy (TXM) reveals dense and granular electrodeposited lithium morphologies in AFLSBs. Therefore, the interplay between reviving inactive lithium for compensating lithium inventory loss and stabilizing lithium electrodeposition endows high electrochemical performance in AFLSBs.