Crystal Engineering Enables Cobalt-Based Metal–Organic Frameworks as High-Performance Electrocatalysts for H₂O₂ Production

Abstract

Metal–organic frameworks (MOFs) with highly adjustable structures are an emerging family of electrocatalysts in two-electron oxygen reduction reaction (2e-ORR) for H2O2 production. However, the development of MOF-based 2e-ORR catalysts with high H2O2 selectivity and production rate remains challenging. Herein, an elaborate design with fine control over MOFs at both atomic and nano-scale is demonstrated, enabling the well-known Zn/Co bimetallic zeolite imidazole frameworks (ZnCo-ZIFs) as excellent 2e-ORR electrocatalysts. Experimental results combined with density functional theory simulation have shown that the atomic level control can regulate the role of water molecules participating in the ORR process, and the morphology control over desired facet exposure adjusts the coordination unsaturation degree of active sites. The structural regulation at two length scales leads to synchronous control over both the kinetics and thermodynamics for ORR on bimetallic ZIF catalysts. The optimized ZnCo-ZIF with a Zn/Co molar ratio of 9/1 and predominant {001} facet exposure exhibits a high 2e– selectivity of ∼100% and a H2O2 yield of 4.35 mol gcat –1 h–1. The findings pave a new avenue toward the development of multivariate MOFs as advanced 2e-ORR electrocatalysts.

Linker length-dependent hydrogen peroxide photosynthesis performance over crystalline covalent organic frameworks

“…S2†) in 0.1 M KCl +10 mM K 3 [Fe(CN) 6 ] as the electrolyte at different rotation speeds. 23,24 The H 2 O 2 selectivity was calculated using the following equation: selectivity (%) = 200 × ( I r / N )/( I d + I r / N ), where I r is the ring current, I d is the disk current and N is the current collection efficiency of the Pt ring electrode ( N = 0.223). The Tafel slope was calculated using the Tafel equation: ( η = a + b log( j ) ( η , j , and b stand for overpotential, measured current density, and Tafel slope, respectively), and a scan rate of 5 mV s −1 was used to obtain the polarization curves for Tafel plots.…”

Self-supporting metal–organic framework-based hydrogen and oxygen electrocatalysts

“…Recently, Zhang et al reported ZnCo-ZIFs with an optimized Zn/Co ratio and predominant {001} facets by finely controlling MOFs at the atomic and nano-scale. 99 Experimental results and DFT calculations indicated that the generation of electron insufficient Co active sites and exposure to the {001} surface are favorable for H 2 O 2 desorption and the two-electron ORR. This work opens a new way for the development of advanced MOF-based electrocatalysts for the two-electron ORR.…”

High performance of visible-light driven hydrogen production over graphdiyne (g-CnH2n−2)/MOF S-scheme heterojunction

“…ZnCo-ZIF with a dodecahedral structure was prepared by a room-temperature chemical method, based on previous reports. [50][51][52] Briefly, 3.24 g of 2-methylimidazole as a precursor was dissolved in 200 mL of methanol, and uniformly dispersed by ultrasound treatment. Zn(NO 3 ) 2 •6H 2 O (1.45 g) and Co(NO 3 ) 2 •6H 2 O (1.45 g) were dissolved in 200 mL of methanol uniformly by ultrasonication.…”