# Unraveling the Role of MoOx Clusters in Ternary Mo/Co3NiOx for Boosting Acidic Oxygen‐Evolution Performance

## TL;DR

This paper introduces a new ternary electrocatalyst, Mo/Co3NiOx, that outperforms commercial catalysts in acidic oxygen evolution reactions due to a unique mechanism involving two pathways working together.

## Contribution

The study introduces a ternary Mo/Co3NiOx electrocatalyst with enhanced acidic OER performance through a synergistic mechanism of AEM and LOM pathways.

## Key findings

- The Mo/Co3NiOx catalyst achieves lower overpotentials and better durability than commercial RuO2 in acidic OER.
- The catalyst's performance is attributed to a synergistic interplay between AEM and LOM pathways.
- Durability is linked to structural stability and the synergistic effect of the ternary heterostructure.

## Abstract

Developing efficient transition metal electrocatalysts with low cost for the acidic oxygen evolution reaction (OER) confronts an enormous challenge. This work reveals the promising potential of ternary Mo/Co3NiOx OER electrocatalysts, exhibiting good overpotentials of 249 mV@10 mA cm−2 and 429 mV@50 mA cm−2 and a small Tafel slope of 219 mV dec−1 in OER tests (in a 0.5 m H2SO4 electrolyte), much better than those for the corresponding com‐RuO2 (330 mV@10 mA cm−2 and 445 mV dec−1). Furthermore, it exhibits good durability, lasting for ≈200 hours at a current density of 10 mA cm−2, which can be attributed to the synergistic effect of the ternary heterostructure. The deactivation of Mo/Co3NiOx catalyst is attributed to the loss of Ni species, which then leads to the structural destruction, corroborated by methods of in situ inductively coupled Plasma‐optical emission spectroscopy and X‐ray photoelectron spectroscopy. Finally, in situ attenuated total reflection‐surface enhanced infrared absorption spectroscopy (ATR‐SEIRAS) combined with DFT results show that the pristine Co3NiOx prefers the adsorbate evolution mechanism (AEM), and proceeds via a synergistic interplay between AEM and lattice oxygen oxidation mechanism (LOM).

The ternary Mo/Co3NiOx outperforms commercial RuO2 in acidic OER tests and exhibits good durability (lasting for ≈200 hours@10 mA cm−2), which is attributed to alteration of AEM pathway (for Co3NiOx carriers) to a synergistic interplay between AEM and LOM pathways.