# Tailoring Intermediate Adsorption Through d‐band Mismatch Strategy of Heterojunction to Achieve Industrial Overall Water Splitting

## TL;DR

This paper introduces a new strategy using a Ni3Mo/Ni3N junction to improve water splitting efficiency by manipulating d-band centers.

## Contribution

The paper proposes a novel d-band mismatch mechanism to explain the synergistic effect between Ni3Mo and Ni3N for enhanced hydrogen and oxygen evolution reactions.

## Key findings

- The Ni3Mo–Ni3N/NF achieves ultra-low overpotentials for HER and OER at various current densities.
- The HER performance of Ni3Mo–Ni3N/NF surpasses that of Pt/C catalysts across all tested current densities.
- The catalyst shows excellent performance in anion exchange membrane water electrolyzers with stable operation for 1000 hours.

## Abstract

Adjusting the d‐band center of catalysts through heterojunction construction represents an effective approach for enhancing the catalytic activity. Nevertheless, the precise modulation pathways of d‐band centers still require systematic elucidation. In this work, a Ni3Mo/Ni3N junction is constructed to investigate d‐band engineering, and a d‐band mismatch mechanism has been proposed for the first time to elucidate the synergistic effect between Ni3Mo and Ni3N for improved HER and OER. Specifically, the dissociation of H2O can be achieved on the Ni3Mo surface while the adjacent Ni3N sites catalyze the subsequent evolution reactions. Remarkably, the Ni3Mo–Ni3N/NF achieves ultra‐low overpotentials of 15 mV (HER) and 155 mV (OER) at 10 mA cm−2, and just 228 mV (HER) and 459 mV (OER) at 1 A cm−2. Most strikingly, the HER performance of Ni3Mo–Ni3N/NF is superior to that of the Pt/C catalyst across all current densities, marking it as a standout among the NiMo‐based catalysts documented so far. Additionally, the Ni3Mo–Ni3N/NF demonstrates outstanding performance in an anion exchange membrane water electrolyzer (AEMWE), delivering the current density of 4 A cm−2 at a mere 2.12 V while maintaining stable operation for 1000 h at 1 A cm−2, showing great potential for practical applications.

This paper demonstrates the fabrication of a Ni3Mo/Ni3N junction to investigate d‐band engineering and elucidate the specific roles of Ni3Mo and Ni3N active sites in improving catalytic activity. Through integrated spectroscopic characterization and first‐principles modeling, for the first time, a d‐band mismatch mechanism has been proposed to elucidate the synergistic effect between Ni3Mo and Ni3N for improved HER and OER.