Tailored anchoring of FeNiOx on carbon nanotubes to enhance local electric field for boosting overall water splitting

Abstract

Developing non-precious metal FeNi based bifunctional electrocatalysts for high-performance overall water splitting is crucial for advancing hydrogen energy technology. However, they commonly suffer lower activity in hydrogen evolution reaction (HER) due to unsuitable intermediates adsorption and delayed electrons transfer. In this work, by a directional arrangement strategy, raft-like FeNiO_x active species were precisely constructed supported on carbon nanotubes (CNTs). This electrocatalyst exhibited significantly improving HER activity under alkaline conditions with a lower overpotential of 70 mV and Tafel slope of 51.6 mV dec⁻¹ at current density of 10 mA cm⁻². Meanwhile, it also maintained superior performance for oxygen evolution reaction (OER), requiring only 205 mV overpotential and a Tafel slope of 74.9 mV dec⁻¹ at the same current density. A cell voltage of just 1.485 V was needed to reach 10 mA cm⁻² in overall water splitting and outperformed commercial Pt/C||IrO₂ electrodes. This promotion was derived from the enhanced local electronic field and electron transport on FeNiO_x rafts induced by confinement effect on CNTs. Moreover, the dynamic optimization of electronic structure at Fe–O–Ni heteronuclear sites further reduced the reaction energy of rate-determining step in both HER and OER reactions. This study provides novel insights into the rational design of electrocatalyst microstructures and precise modulation of electronic properties, thereby accelerating the commercialization of overall water splitting technology.