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

Abstract

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 1.71V to maintain stable operation at 1 A cm-2 over a 1000-hour period.