Single‐Atom Pd‐N₄ Catalysis for Stable Low‐Overpotential Lithium‐Oxygen Battery

Abstract

especially the sluggish dissociation kinetics of Li 2 O 2 , which lead to high charge overpotential and undesirable parasitic reactions. [12][13][14][15] Considerable parasitic reactions are largely detrimental to the reversible Li 2 O 2 formation/decomposition, which in turn results in low round-trip efficiency and inferior rechargeability for Li-O 2 batteries. [16][17][18][19] Therefore, a rational design of efficient electrocatalysts toward decreasing overpotential, enhancing round-trip efficiency, and improving cycling stability is one of the significant strategies to solve the problems for Li-O 2 batteries.To facilitate the reversible decomposition of Li 2 O 2 , numerous efforts have been devoted to explore the cathode catalysts, including carbons, [20][21][22][23] precious metals, [24][25][26][27][28] and nonprecious metal oxides. [29][30][31][32] Among all the candidates explored, palladium [12,33,34] and its oxides [35] have shown some promise in decreasing charge overpotential and enhancing round-trip efficiency for Li-O 2 batteries. A common problem of these studies is that excessive palladium is used among solid catalysts, which leads to low utilization of active sites. The scarcity and high cost of palladium, however, have severely restricted its practical applications as a cathode catalyst for Li-O 2 batteries. Therefore, it is of crucial importance to maximize its accessible active sites to improve the catalytic activity by regulating the inherent properties of the catalysts. Owing to the utmost utilization efficiency of atoms and unique electronic properties, single-atom catalysts have exhibited superior catalytic activity in the fields of catalysis, including fuel cells, [36,37] water electrolysis [38,39] and O 2 /CO 2 /N 2 reduction reactions, [40][41][42][43] and so on. Nevertheless, relatively only a few studies involving single-atom catalysts in aprotic Li-O 2 batteries were reported. [44][45][46] For example, Hu et al. lowered the overpotential using Ru single-atoms anchored on nitrogen-doped porous carbon (Ru SAs-NC) as a cathode catalyst for Li−O 2 batteries. [44] Xu et al tuned Li 2 O 2 formation and decomposition routes with a single atom Co catalyst. [45] Yin et al fabricated isolated cobalt atoms embedded in ultrathin nitrogen-rich carbon (Co-SAs/N-C) and the redox kinetics is enhanced. [46] Single-atom catalysts have indeed exhibited some prospects in aprotic Li-O 2 batteries, but the overpotential is still not low enough, especially the charge potential is not stable. The charge potential usually demonstrates an obvious decrease in the initial charge state but it rises a lot with the increase of capacity or the charge-discharge cycles. Therefore, how to further effectively reduce the charge potentialThe critical challenge for Li-O 2 batteries lies in the large charge overpotential, leading to undesirable side reactions and inferior cycle stability. Singleatom catalysts have shown promising prospects in expediting the kinetics of oxygen evolution reaction (OER) for Li-O 2 batteries. Ho...

Water‐Trapping Single‐Atom Co‐N4/Graphene Triggering Direct 4e− LiOH Chemistry for Rechargeable Aprotic Li–O2 Batteries

“…Furthermore, inductively coupled plasma mass spectrometry (ICP‐MS) analysis showed the mass percentage of cobalt in the Co‐SA‐rGO sample was about 1.31 wt % (Table S1, Supporting Information). The X‐ray diffraction (XRD) patterns of Co‐SA‐rGO displayed only two peaks at 26.4° and 44.4° assigned to the (002) and (101) planes of Graphite‐2H (PDF#41‐1487), [ 45 ] indicating that there are no cobalt particles in the sample (Figure 2d). Raman spectrum of Co‐SA‐rGO demonstrated two peaks at 1350 and 1580 cm −1 , well assigned to the D‐band (lattice vibration leaving the center of the Brillouin region, characterizing structural defects) and G‐band (the in‐plane vibration of sp 2 carbon) of carbon.…”

Nanoengineering of Cathode Catalysts for Li–O2 Batteries

“…N-doped carbon spheres with Pd−N 4 coordination (Pd SAs/NC) have been reported to display exceptional capabilities. 86 As reflected by TEM, Pd SAs/NC showed a uniform hollow spherical structure with an approximate diameter of 200 nm (Figure 9d). EDXS elemental mapping presented the homogeneous distribution of C, N, and Pd on the Pd SAs/NC surface (Figure 9e).…”

“…28,84,85 This modulation of discharge products can alter the charging process and charge overpotential, ultimately enhancing the battery's cycling stability. 32,86,87 Cathode catalysts consisting of rGO and iridium nanoparticles (Ir-rGO) have been employed in high-performance Li−O 2 batteries, where the main discharge product is LiO 2 rather than Li 2 O 2 (Figure 5a). 21 The experimental results coupled with density functional theory (DFT) analysis demonstrated a strong correlation between the formation of LiO 2 and the lattice matching of LiO 2 and Ir 3 Li (Figure 5b).…”

First Principles Study of the Structure–Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries

“…The values of , , and are decreased in the order of W 4 C 3 O 2 (0.38 V/0.25 V/0.63 V) < W 3 C 2 O 2 (0.45 V/0.39 V/0.84 V) < W 2 CO 2 (0.54 V/0.48 V/1.02 V). Moreover, the values of for W n+1 C n and W n+1 C n O 2 MXenes are higher than those of , indicating the slower kinetics of the OER during the charging process, which may lead to poor cyclic stability [ 54 ]. This is attributed to the strong adsorption of the Li x O 2 produced during the discharge process, which makes it difficult to reversibly decompose, resulting in continuous accumulation [ 55 , 56 ].…”