Micro-Pyrolysis Perturbation Promotes Electrocatalytic Activity of Tetranuclear Nickel Clusters

Abstract

As for the preparation of efficient and stable electrocatalysts containing transition metal heteroatoms by high-temperature pyrolysis is intriguing. However, studies on the pyrolysis of complexes in low-temperature range to obtain efficient catalytic transport platforms are rare. Herein, we propose a micro-pyrolysis perturbation strategy in constructing nickel molecular cluster-based bifunctional electrocatalysts, derived from a case of the tetranuclear Schiff-based nickel molecular cluster Ni4 (Ni4(II)C46H68N4O18) with N, O coordination mode. the crystal structure undergoes mild decomposition of peripheral ligands during the pyrolysis process are revealed by in situ Thermogravimetry-mass spectrometry (TG-MS) and ex situ synchrotron-based X-ray absorption spectroscopy (XAS) technology. Besides, the metal active center inside the nickel molecular cluster Ni-O is able to be exposed on the surface in micro-pyrolysis perturbation rather than being covered or destroyed under traditional high-temperature pyrolysis. The bifunctional catalyst Ni4-350 displays a low overpotential of 247 mV for the OER, and 1.366 V for the UOR at 10 mA·cm-2, which is also stable in alkaline medium for 10 hours of continuous running. This model study highlights that the micro-pyrolysis perturbation strategy can provide stable highly active centers while retaining the host structural framework in Ni-based clusters with promising potential application in low-potential OER/UOR electrocatalysts.

Keywords: tetranuclear nickel clusters, micro-pyrolysis, Amorphous phase, bifunctional electrocatalysts