Curvature-tailored Sub-50 nm TiO2 support for enhanced performance and durability of Ir catalysts in PEM water electrolysis

초록

Rational design of oxide supports for Ir catalysts is a highly promising approach to enhance proton exchange membrane water electrolysis (PEMWE) performance and durability while minimizing Ir usage. Here, we report a curvature-engineered TiO2 support synthesized via a polystyrene (PS) templating method to modulate the Ir nanoparticle dispersion and catalyst-support interaction. By controlling the size of PS spheres, interconnected hollow TiO2 (h-TiO2) structures with tunable curvature can be obtained. The curvature of TiO2 support alters the oxidation state of Ir; higher curvature facilitates electron transfer from Ir to TiO2, increasing the Ir(IV)/Ir(III) ratio and consequently lowering intrinsic activity. In contrast, the electrochemical surface area (ECSA) increased with curvature, enabled by controlled Ir nanoparticle dispersion and connectivity within our unique h-TiO2 structure. By optimizing the trade-off characteristics associated with curvature, we achieved superior mass activity for Ir/h-TiO2 (262 A/gIr at 1.55 VRHE), approximately 2.2 times greater than that of Ir black (119 A/gIr at 1.55 VRHE), as well as improved durability. PEMWE single-cell employing the optimized Ir/h-TiO2 with 0.5 mgIr cm-2 demonstrated comparable performance (1.648 V at 1 A cm-2) to Ir black with 0.7 mgIr cm-2 (1.645 V at 1 A cm-2), indicating its practical applicability with approximately 30 % less Ir usage. This work highlights curvature-tuned support engineering as a viable route to optimize Ir usage.

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