Air–Cathode Interface-Engineered Electrocatalyst for Solid-State Rechargeable Zinc–Air Batteries

Abstract

Solid-state rechargeable zinc–air batteries (ZABs) are gaining interest as a class of portable clean energy technology due to their advantages such as high theoretical energy density, intrinsic safety, and low cost. It is expected that an appropriately triple-phase boundary (TPB) engineered, bifunctional oxygen reaction (OER and ORR) electrocatalyst at the air–electrode of ZABs can redefine the performance characteristics of these systems. To explore this possibility, an electrode material consisting of manganese–cobalt-based bimetallic spinel oxide (MnCo2O4)-supported nitrogen-doped entangled graphene (MnCo2O4/NEGF) with multiple active sites responsible for facilitating both OER and ORR has been prepared. The porous 3D graphitic support significantly affects the bifunctional oxygen reaction kinetics and helps the system display a remarkable catalytic performance. The air electrode consisting of the MnCo2O4/NEGF catalyst coated over the gas diffusion layer (GDL) ensures the effective TPB, and this feature works in favor of the rechargeable ZAB system under the charging and discharging modes. As an important structural and functional attribute of the electrocatalyst, the porosity and nitrogen doping in the 3D conducting support play a decisive aspect in controlling the surface wettability (hydrophilicity/hydrophobicity) of the air electrode. The fabricated solid-state rechargeable ZAB device with the developed electrode displayed a maximum peak power density of 202 mW cm–2, which is significantly improved as compared to the one based on the Pt/C + RuO2 standard catalyst pair (124 mW cm–2). The solid-state device which displayed an initial charge–discharge voltage gap of only 0.7 V at 10 mA cm–2 showed only a small increment of 86 mV after 50 h.

Microporous 3D-Structured Hierarchically Entangled Graphene-Supported Pt3Co Alloy Catalyst for PEMFC Application with Process-Friendly Features

“…Figure b shows the comparative Raman spectra of the NEGF, pNEGF, and Pt 3 Co/pNEGF. The peaks that appeared at 1350 and 1590 cm –1 are credited to the G and D bands, respectively . In the case of the NEGF and pNEGF, the measured I D / I G ratios are 1.25 and 1.32, respectively.…”

“…However, with the Co incorporation into Pt, the resulting PtCo/pNEGF and Pt 3 Co/ pNEGF show a shift in the positions of the (111) and (200) peaks. 39,40 The observed XRD peak shifts for PtCo/pNEGF and Pt 3 Co/pNEGF (39.8°) are due to the contraction of the Pt lattice after the alloy formation. 38 Moreover, the alloy structure has been confirmed with the standard JCPDS cards of the Pt 3 Co alloy phase (JCPDS no.…”

“…This controlled distribution of the Pt 3 Co nanoparticles over the surface and the edge of the graphene mediated by the defect sites and the doped sites of the heteroatom (N) is an important structural benefit to the system as this can suppress the self-agglomeration possibility of the nanoparticles under the triggered conditions of the electrochemical environments. 40 In addition, the fine distribution of the active sites at the edges of the graphene layers of its 3D framework is expected to provide better reactant accessibility due to their relatively exposed nature in the catalyst framework. 42 The inset image in Figure 2c shows that the Pt The pore size distribution comparison profiles using the DFT method of the NEGF, pNEGF, and Pt 3 Co/pNEGF shown in Figure 3a suggest that the porosity of the NEGF mostly resides in the region of 5−20 nm, indicating the presence of mesoporosity.…”

“…38 Aside from these, the presence of the graphitic carbon support with homogeneously doped nitrogen centers (N-doped sites) creates metal anchoring sites and improves the metal−support interaction. 39,40 This helps in achieving better durability in the harsh electrochemical conditions of the PEMFC operation. 41 Furthermore, in the self-assembled 3D graphene support, the pores are mostly distributed in the meso-/macroporous region, which has less access to the subnanometer-sized Pt alloy particles.…”

Wood‐Derived Continuously Oriented Three‐Phase Interfacial Channels for High‐Performance Quasi‐Solid‐State Alkaline Zinc Batteries

“…[ 7 ] Despite the successful construction of the aforementioned hybrid batteries and the associated performance improvement, the problems of the Zn–air batteries segment, in particular, the sluggish kinetics of the electrocatalytic reaction due to the imperfect matching of the gas diffusion layer (GDL) and the cathode, still profoundly limit the specific output capacity and energy efficiency of hybrid Zn batteries. [ 8 ] The additional GDL on the top of the active materials layer in hybrid Zn batteries is critical for the formation of a three‐phase interface involving oxygen (gas phase), a catalyst (solid phase), and an electrolyte (liquid phase), in which the three‐phase interface has a significant impact on the Zn–air battery portion of the hybrid batteries, mainly the availability of reaction gases (O 2 ), the transfer of reaction products (H 2 O), and the provision of active sites for the electrocatalytic oxygen reduction/evolution reaction (ORR/OER). However, the additional GDL is often not perfectly matched to the cathode, leaving the three‐phase interface confined to the narrow space between the active materials layer and the GDL.…”