d-Orbital steered active sites through ligand editing on heterometal imidazole frameworks for rechargeable zinc-air battery

Abstract

The implementation of pristine metal-organic frameworks as air electrode may spark fresh vitality to rechargeable zinc-air batteries, but successful employment is rare due to the challenges in regulating their electronic states and structural porosity. Here we conquer these issues by incorporating ligand vacancies and hierarchical pores into cobalt-zinc heterometal imidazole frameworks. Systematic characterization and theoretical modeling disclose that the ligand editing eases surmountable energy barrier for *OH deprotonation by its efficacy to steer metal d-orbital electron occupancy. As a stride forward, the selected cobalt-zinc heterometallic alliance lifts the energy level of unsaturated d-orbitals and optimizes their adsorption/desorption process with oxygenated intermediates. With these merits, cobalt-zinc heterometal imidazole frameworks, as a conceptually unique electrode, empowers zinc-air battery with a discharge-charge voltage gap of 0.8 V and a cyclability of 1250 h at 15 mA cm–2, outperforming the noble-metal benchmarks.

Recent Advances on MOF Derivatives for Non-Noble Metal Oxygen Electrocatalysts in Zinc-Air Batteries

“…Besides, owing to their similar topological structures and unit cell parameters of ZIF-67 and ZIF-8, several works explored the potential of using these MOF hybrids as a platform to prepare transition metal doped carbon composites [ 125 – 130 ]. For example, the Yin group [ 131 ] put forward the synthesis of MO-Co@N-doped carbon (M means metal Zn or Co) by the pyrolysis of Co-contained ZIF-67 and Zn-contained ZIF-8 hybrid MOFs.…”

Rational Design of MOF-Based Materials for Next-Generation Rechargeable Batteries

“…In addition, the direct growth of CoZn-ZIF nanosheet arrays on Ni foam support and its hierarchical porosity can ensure fast electron transfer and mass transportation in Zn-air batteries [180,181]. 2D MXene with high electrical conductivity, surface electronegativity, and good stability are potential substrates that may alter the electrophilicity of the active centers of MOFs and therefore tune their catalytic properties.…”

Mesoporous Zeolitic Imidazolate Frameworks

“…[13][14] As a result, ZIFs generally encounter the barrier of mass transfer in the diffusion-limited processes because of the intrinsic microporous structure. [15][16][17][18] Therefore, much effort has been devoted to constructing the hierarchical pore structures of ZIFs by incorporating the mesopores or macropores, including templating, [19][20][21][22][23] etching, [24][25] coating, [26][27] trapping, 28 and competing coordination. 16 However, these attempts fail to obtain the ordered distribution of the meso/macroporous structures.…”