Magnesium-assisted fabrication of platinum single-atom electrocatalysts anchored on intrinsic carbon defects for efficient HER and ORR performance

Carbon-based single-atom catalysts (SACs) offer exceptional atom utilization efficiency and tunable active sites; however, the precise engineering of intrinsic carbon defects, such as vacancies and edges, without heteroatom interference remains a significant challenge. Herein, we developed a magnesium-assisted strategy for fabricating platinum single-atom electrocatalysts anchored solely on intrinsic carbon defects (denoted as Pt_SACs-C-1100), utilizing a nitrogen-free Mg-gallate MOF as a precursor. During pyrolysis at 1100 °C, uniformly dispersed Mg²⁺ sites serve as in situ etchants to create a hierarchical porous network rich in structural defects. Spectroscopic and theoretical analyses confirmed that the Pt atoms anchored at the defect sites form Pt-C₂ coordination configurations. This unique structure optimizes the hydrogen adsorption energy (∆G_H* = 0.0391 eV), endowing the catalyst with exceptional activity for the hydrogen evolution reaction (HER: η₁₀ = 16.5 mV in acid and 50 mV in alkali). With a Pt loading of 4.4 wt%, Pt_SACs-C-1100 exhibits higher mass activities 6.6–9.4 times higher than those of commercial 20 wt% Pt/C. Moreover, Pt_SACs-C-1100 also shows excellent oxygen reduction reaction activity (E_1/2 = 0.866 V). When deployed in a flow Zn–air battery, it achieves a peak power density of 230.8 mW cm⁻² and sustains stable operation for > 200 h, demonstrating practical viability for energy conversion devices.