Au@NiS_x Yolk@Shell Nanostructures as Dual-Functional Electrocatalysts for Concomitant Production of Value-Added Tartronic Acid and Hydrogen Fuel

Efficient glycerol electrooxidation reaction (GEOR) over gold@nickel sulfide (Au@NiS_x) yolk@shell nanostructures is demonstrated, achieving ≈50.4% glycerol conversion at 10 h, 92.6% selectivity toward three-carbon products, and 90.7% total Faradaic efficiency. By regulating the electrode potential, tartronic acid (TART), one of the highest value-added intermediates, can be produced with a selectivity as high as 43.1% and a yield of 45.6 µmol cm⁻² h⁻¹. A combination of ex situ microstructural analysis, operando Raman, and operando X-ray absorption measurements reveals a dynamic surface reconstruction course from Au@NiS_x to Au@NiS_x/NiOOH during the glycerol oxidation process. The unique reconstructed architectures featuring conductive interior NiS_x components and active surface high-valence Ni³⁺ species account for the superior GEOR performance. Further integration of GEOR with hydrogen evolution reaction is realized by employing Au@NiS_x as both anode and cathode electrocatalysts in a two-electrode configuration. Concomitantly production of TART and hydrogen fuel is accomplished. This study demonstrates that Au@NiS_x not only can convert glycerol to TART with remarkable efficiency and selectivity, but also can produce hydrogen at a moderate level. The findings from this study can facilitate the development of dual-functional electrocatalysts capable of producing high-value products at both the cathode and anode sides.