Work function-engineered high-entropy oxide for low-voltage glucose oxidation and hydrogen generation

초록

We report a novel rapid CO2 laser method for synthesizing binder-free catalysts, including a thin layer of high-entropy oxide (HEO) on nickel foam (HEO@NF). HEO@NF was further used as a binder-free catalyst for low-voltage glucose oxidation coupled with water electrolysis. A "work function engineering strategy" was introduced to boost the electro-oxidation performance of the catalyst, particularly for the glucose oxidation reaction (GOR). HEO@NF exhibits a low oxidation potential of 1.22 V for the GOR at 10 mA cm-2. It also shows excellent stability for both the OER and the GOR over 100 h at 50 mA cm-2. 1H NMR analysis reveals formate and glycolate as the main products of glucose oxidation. In overall glucose oxidation coupled electrolysis, the HEO@NF||Pt/C/NF pair requires only 1.37 and 1.67 V to achieve a current density of 10 and 50 mA cm-2, respectively. In situ Raman spectroscopy identifies the key role of A1g corresponding to the octahedral site (MO6) of spinel oxides in the GOR, whereas the formation of cobalt oxyhydroxide (CoO(OH)) is observed in the OER. Density functional theory (DFT) calculations identify Cu as the principal active site for the GOR and Co as essential for the OER. Notably, the DFT-predicted downward shift of the d-band center correlates well with the experimentally observed reduction in work function measured by ultraviolet photoelectron spectroscopy, providing direct theoretical support for the proposed work-function engineering strategy. Overall, the CO2 laser-assisted synthesis of HEO@NF demonstrates strong potential for practical, low-energy hydrogen production coupled with the selective oxidation of glucose into value-added products, formate, and glycolate.

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