Boosting Energy Efficiency and Stability of Li–CO₂ Batteries via Synergy between Ru Atom Clusters and Single‐Atom Ru–N₄ sites in the Electrocatalyst Cathode

Abstract

climate change. [2] Many countries established legislations to limit the CO 2 emissions, targeting at carbon neutrality. [3] Meanwhile, efficient and clean battery systems are being developed. The lithium-ion battery (LIB) is the most successful and widely used system. [4] However, the relatively low energy density severely hindered the applications of LIBs. Recently, metalair batteries have attracted much attention due to their ultrahigh energy density. [5] However, most of them need to work in a pure oxygen environment. [6] Therefore, an energy-storage system directly utilizing CO 2 gas as redox medium is highly favorable.In 2013, Archer and co-workers proposed the concept of Li-CO 2 battery for CO 2 capture and energy storage, in which Li metal and CO 2 gas are the active materials in the anode and cathode side, respectively. [7] During discharge, Li + reacts with CO 2 to generate Li 2 CO 3 and carbon as discharge products, which is a CO 2 reduction reaction (CO 2 RR) process described as 4Li + + 3CO 2 + 4e − → 2Li 2 CO 3 + C. [8] In the reverse charging process, a CO 2 evolution reaction (CO 2 ER) occurs by decomposing Li 2 CO 3 into Li + and CO 2 gas. Many merits are identified for the Li-CO 2 battery system like the direct employing greenhouse gas of CO 2 and the high theoretical energy density of 1876 Wh kg −1 . [9] However, issues including but not limited to the large overpotential, poor cycling performance, and inferior rate capability significantly hinder the application of Li-CO 2 batteries. One dominating reason for these issues is the intrinsically sluggish kinetics of the CO 2 RR and CO 2 ER processes.Therefore, the key task for the practical application of Li-CO 2 batteries is to develop highly efficient catalysts toward the CO 2 RR and CO 2 ER. Large varieties of catalysts, such as carbon-based catalysts, [6,8a,b,10] single-metal-atom catalysts, [11] adjacent metal atoms catalyst, [12] nanostructured metal/alloy catalysts, [13] and transition metal compound catalysts [14] were developed for Li-CO 2 batteries to facilitate the CO 2 reduction and promote the decomposition of Li 2 CO 3 . Metallic ruthenium (Ru) and Ru-based materials is an important catalyst family for the CO 2 RR and CO 2 ER. [15] Ru catalyst has intrinsic advantage in The Li-CO 2 battery is a novel strategy for CO 2 capture and energy-storage applications. However, the sluggish CO 2 reduction and evolution reactions cause large overpotential and poor cycling performance. Herein, a new catalyst containing well-defined ruthenium (Ru) atomic clusters (Ru AC ) and single-atom Ru-N 4 (Ru SA ) composite sites on carbon nanobox substrate (Ru AC+SA @NCB) (NCB = nitrogen-doped carbon nanobox) is fabricated by utilizing the different complexation effects between the Ru cation and the amine group (NH 2 ) on carbon quantum dots or nitrogen moieties on NCB. Systematic experimental and theoretical investigations demonstrate the vital role of electronic synergy between Ru AC and Ru-N 4 in improving the electrocatalytic activity toward the C...

In situprecise anchoring of Pt single atoms in spinel Mn3O4for a highly efficient hydrogen evolution reaction

“…Single-atom catalysts (SACs) provide the advantage of maximizing the utilization of each metal center while affording even higher performance than their aggregated clusters or nanoparticles. 14–23 For Pt-based catalysts, the slow alkaline HER kinetics are due to a high energy barrier that needs to be overcome for the water dissociation step. 24 Therefore, the rational design of a catalyst structure and properties to modulate the concentration and type of active sites is essential for an efficient and stable HER catalytic process.…”

Reconstruction of Highly Dense Cu−N4Active Sites in Electrocatalytic Oxygen Reduction Characterized by Operando Synchrotron Radiation

“…More Cu 2 + is reduced to Cu + when the applied potential turned to the lower potentials of 0.50 and 0.30 V. Concurrently, the structural evolution from CuÀ N 4 to CuÀ N 3 can be detected, in which one CuÀ N bond among the four symmetrical CuÀ N bonds in the original CuÀ N 4 configuration is broken and the resultant suspended pyridinic N is saturated by a proton. [44,45] The EXAFS spectra of Cu K-edge were further displayed in Figure 5b. Concretely, the main CuÀ N bond concentrated around 1.5 Å could be obviously observed.…”

The Progress and Outlook of Metal Single-Atom-Site Catalysis

“…Similar electron transfer was reported by Han et al, who prepared RuAC+SA@NCB with Ru atomic cluster (RuAC) and singleatom Ru−N 4 (RuSA) composite sites on nitrogen-doped carbon nanobox (NCB) for application in Li−CO 2 batteries. 115 The electronic structure of the Ru−N 4 sites was modified by the adjacent RuAC, which optimized the interaction between the Ru−N 4 sites and *Li adsorbed on active Ru sites to generate hydrogen and complete the HER kinetic process. The regulation of electronic structure through the electronic interaction between NPs and M 1 sites is enlightening for the design of advanced catalysts.…”

“…The enhancement was attributed to the introduction of Ru NPs, which manipulated the electronic structure of neighboring Ru 1 sites, reduced the adsorption capacity of water, and lowered the thermodynamic barriers for electron transfer. Similar electron transfer was reported by Han et al, who prepared RuAC+SA@NCB with Ru atomic cluster (RuAC) and single-atom Ru–N 4 (RuSA) composite sites on nitrogen-doped carbon nanobox (NCB) for application in Li–CO 2 batteries . The electronic structure of the Ru–N 4 sites was modified by the adjacent RuAC, which optimized the interaction between the Ru–N 4 sites and *Li 2 C 2 O 4 .…”