Modulating Built-In Electric Field Strength in Ru/RuO₂ Interfaces through Ni Doping to Enhance Hydrogen Conversion at...

Improving the alkaline hydrogen evolution reaction (HER) efficiency is essential for developing advanced anion exchange membrane water electrolyzers (AEMWEs) that operate at industrial ampere-level currents. Herein, we employ density functional theory (DFT) calculations to identify Ni-RuO₂ as the leading candidate among various 3d transition metal-doped M-RuO₂ (where metal M includes Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn). The incorporation of Ni atoms facilitates the partial reduction of RuO₂, resulting in the formation of a Ni-Ru/RuO₂ interface having a significant built-in electric field (BIEF) during electrochemical reactions. The resulted BIEF enhances electron transfer across the interface, which is critical in lowering energy barriers and accelerating the hydrogen evolution reaction (HER) kinetics. As a result, the Ni-RuO₂ catalyst exhibits an overpotential of 134 mV at 1 A cm^-2 and a low Tafel slope of 20.85 mV dec^-1, with just 0.03 mg cm^-2 of Ru loading. The highly effective BIEF, therefore, plays a pivotal role in the catalyst's remarkable performance, allowing the Ni-RuO₂-based AEMWE to require only 1.71 V to maintain stable operation at 1 A cm^-2 over a 1000-hour period.