Rational Design of In Situ-Grown Hierarchical Carbon Nanofiber−MXene Nanointerfaces with Iron−Nickel Oxide Nanoarchitectures for Bifunctional Electrocatalysis

This study investigates the electrocatalytic performance of iron- and nickel oxide-dispersed carbon nanofibers anchored on Ti3C2Tx MXene (FeO−CNF@MX and NiO−CNF@MX), synthesized via chemical vapor deposition (CVD), for alkaline water splitting. The tip-growth mechanism, structural uniformity, and hierarchically engineered features achieved through CVD promote efficient charge transfer during both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), while the high conductivity of Ti3C2Tx further enhances electron transport. For HER, NiO−CNF@MX exhibits the best activity, with an overpotential of 490 mV at 10 mA/cm2, followed by FeO−CNF@MX (520 mV). These values are lower than those of pristine FeO−CNF and NiO−CNF, indicating that anchoring metal oxides on MXene sheets enhances charge transfer and reduces interlayer resistance while also accelerating hydrogen adsorption and desorption kinetics. For OER, NiO−CNF@MX again outperforms, requiring an overpotential of 300 mV at 10 mA/cm2, and FeO−CNF@MX shows 360 mV. Additionally, a prototype electrolyzer further explores the possibility of a bifunctional electrocatalyst as FeO−CNF@MX achieves a lower cell voltage (2.2 V) compared to NiO−CNF@MX (2.7 V) at a current density of 10 mA/cm2. Additionally, the stability of these electrocatalysts shows promising results, with a voltage drift of around 0.2−0.3 V observed during a one-day stability test. Overall, this work highlights the promise of CVD-grown FeO−CNF@MX and NiO−CNF@MX as efficient and consistent electrocatalysts for alkaline water splitting, emphasizing the importance of the synthesis strategy and electrode design in advancing sustainable hydrogen production.