Three-Phase Heterojunction NiMo-Based Nano-Needle for Water Splitting at Industrial Alkaline Condition

Abstract Constructing heterojunction is an effective strategy to develop high-performance non-precious-metal-based catalysts for electrochemical water splitting (WS). Herein, we design and prepare an N-doped-carbon-encapsulated Ni/MoO 2 nano-needle with three-phase heterojunction (Ni/MoO 2 @CN) for accelerating the WS under industrial alkaline condition. Density functional theory calculations reveal that the electrons are redistributed at the three-phase heterojunction interface, which optimizes the adsorption energy of H- and O-containing intermediates to obtain the best Δ G H* for hydrogen evolution reaction (HER) and decrease the Δ G value of rate-determining step for oxygen evolution reaction (OER), thus enhancing the HER/OER catalytic activity. Electrochemical results confirm that Ni/MoO 2 @CN exhibits good activity for HER ( ƞ - 10 = 33 mV, ƞ - 1000 = 267 mV) and OER ( ƞ 10 = 250 mV, ƞ 1000 = 420 mV). It shows a low potential of 1.86 V at 1000 mA cm −2 for WS in 6.0 M KOH solution at 60 °C and can steadily operate for 330 h. This good HER/OER performance can be attributed to the three-phase heterojunction with high intrinsic activity and the self-supporting nano-needle with more active sites, faster mass diffusion, and bubbles release. This work provides a unique idea for designing high efficiency catalytic materials for WS.