MXene-booste d MOF-derive d hierarchical porous C, N-doped In2 O3 /Gd2 MoO6 heterostructures with rich oxygen vacancies enable highly efficient bifunctional electrocatalysts for water/seawater electrolysis

초록

Developing efficient non-noble metal catalysts is crucial for reducing costs and addressing the scarcity issues associated with noble-metal-based electrocatalysts for water splitting. In this study, metal-organic frameworks-derived C, N-doped In2O3 with abundant oxygen vacancies were synthesized by pyrolysis of NH2-MIL-68(In). To enhance its performance, 3D flower-like xGd2MoO6 ( x = 10, 20, 30, 40, and 50 wt%) was integrated with In2O3 and 5 % MXene, forming a composite denoted as x-GInMx. The bifunctional 4-GInMx@nickel foam (NF) electrocatalyst exhibited outstanding performance, achieving low hydrogen evolution reaction (HER) overpotentials (eta) of 110 and 104 mV with Tafel slopes of 83 and 76 mV/dec at current density ( J ) of 10 mA/cm2 in alkaline freshwater (FW) and natural seawater (SW), respectively. Additionally, it demonstrated low oxygen evolution reaction (OER) eta of 160 and 200 mV, along with Tafel slopes of 97 and 77 mV/dec in FW and SW, respectively. Notably, 4-GInMx@NF outperformed IrO2 @NF and approached the performance of Pt/C@NF, while also demonstrating excellent stability in corrosive SW environments. The overall water-splitting electrolyzer assembled with 4-GInMx@NF||4-GInMx@NF electrode achieved low cell voltages of 1.56 (FW) and 1.62 V (SW) at 10 mA/cm2, outperforming the benchmark Pt/C@NF||IrO2 @NF electrolyzer. Additionally, density functional theory calculations provide evidence of improved catalytic activity and reaction kinetics of the GInMx heterostructures by analyzing the underlying HER and OER pathways. The exceptional performance of 4-GInMx is attributed to its high surface area, synergistic effects, multiple active sites, enhanced electrical conductivity, and resistance to structural degradation. This work highlights 4-GInMx as a promising, cost-effective bifunctional electrocatalyst for sustainable H2 production, reduced carbon emissions, and enhanced environmental protection. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

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