Immobilization of transition metal (Ni, Cu, and Co)-based colloidal nanoscale materials for the oxygen evolution...

The rational design of high-performance electrocatalysts for the oxygen evolution reaction (OER) is the holy grail for clean energy conversion and storage, aimed at mitigating the ever-growing energy demands. However, the inherent sluggish kinetics of the OER remain the primary bottleneck, consequently impeding overall water splitting for efficient hydrogen production. In this regard, ultrasmall metal nanoclusters (NCs, size ≤ 3 nm) or nanoscale materials with tunable physicochemical properties have recently emerged, offering unparalleled opportunities for manipulating the catalytic efficiency and electronic structure at the atomic level. Herein, we report a rational design of transition metal (Ni, Cu, and Co)-based colloidal nanoscale materials immobilized on an N-doped carbon (NC) support for the OER. The structure, size, and electronic properties were investigated using UV-vis, photoluminescence (PL), Fourier transform infrared (FTIR), and energy-dispersive X-ray (EDX) spectroscopies, high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements demonstrated encouraging OER performance, where NiNCs@NC, CoNCs@NC, and CuNCs@NC achieved a current density of 10 mA cm^-2 at operational voltages of 1.45, 1.48, and 1.51 V, respectively. Reasonable Tafel slopes and electrochemically active surface area (ECSA) were observed, following the trend of operational potential, indicating an inherent link between the structure-property relationship and kinetics of the OER. Long-term electrochemical testing revealed good durability over 10 hours for all samples, with NiNCs@NC presenting exceptional persistent performance for over 50 hours. Comprehensive structural and electrochemical studies indicated that the improved OER performance stems from the synergistic integrations of thiol-protected monometallic nanoscale materials with the NC support. In a nutshell, this study provides a viable strategy for immobilizing surface-functionalized colloidal nanoscale materials for electrocatalysis, efficiently bridging homogeneous and heterogeneous catalysis.