Just add water to split water: ultrahigh-performance bifunctional electrocatalysts fabricated using eco-friendly heterointerfacing of NiCo diselenides

Abstract

Electrochemical water splitting is one of the most promising ways for clean hydrogen energy production. Along with using earth-abundant, atomically engineered catalysts that are highly active and stable, clean, chemical-waste-free catalyst production—using minimum resources—is a major hurdle toward achieving zero-carbon-emission commercial operations. Herein, we propose a clean way to fabricate NiSe₂–CoSe₂ on nickel–cobalt foam (NCF) using pure water for the in situ sprouting of NiCo layered double hydroxide (LDH) precursors. The excellent electrocatalytic activity for overall water splitting in alkaline electrolytes is highlighted by the overpotentials of NiSe₂–CoSe₂/NCF for delivering current densities of 10 and 400 mA cm⁻² (j₁₀ and j₄₀₀, respectively) at only 24 and 257 mV for hydrogen evolution reaction (HER) and 250 and 346 mV for oxygen evolution reaction (OER), as well as the fast reaction kinetics affording small Tafel slope values of 24 (HER) and 48 (OER) mV dec⁻¹, respectively. NiSe₂–CoSe₂/NCF exhibits excellent electrocatalytic performance and structural stability, evidenced by the unchanged polarization curve after 10⁴ cycles of CV tests and low decay of high current density (j₁₀₀) after 100 h of HER and OER measurements. Theoretical analysis revealed that the Co atoms dispersed on the heterointerfaces between the NiSe₂ and CoSe₂ phases act as the electrocatalytic sites.