# Chromium Cation‐Induced Self‐Reconstruction of a Stable and High Performance Boride‐derived Electrocatalyst for Oxygen Evolution Reaction

## TL;DR

Scientists created a new electrocatalyst using chromium to improve the efficiency of water splitting for oxygen production.

## Contribution

A scalable synthesis method for a chromium-iron-nickel boride electrocatalyst with enhanced oxygen evolution reaction performance is introduced.

## Key findings

- Chromium incorporation leads to self-reconstruction of the catalyst, improving OER kinetics and turnover frequency.
- DFT calculations show chromium narrows the metal-d/boron-p band center gap, enhancing catalytic activity.
- The Δɛd-p is identified as a key electronic descriptor for optimizing OER performance.

## Abstract

The rational design of efficient electrocatalysts for the oxygen evolution reaction (OER), holds the key to advancing the overall electrolytic water splitting performance. Here, a scalable one‐pot synthesis of a stable chromium─iron nickel boride (Cr─FeNiB) electrocatalyst is reported for OER in which nickel‐boron sites are micro‐environmentally modified through interactions with iron and chromium. Comprehensive, correlative electrochemical, structural, and chemical analyses reveal the formation of amorphous‐crystalline core‐shell structures that transform into nanosheets upon activation with enhanced water oxidation catalytic activity. The enhanced catalytic performance is attributed to the chromium‐induced chemical self‐reconstruction of the catalyst, which facilitates favorable OER kinetics, increased turnover frequency, and a synergistic effect between metal and boron constituents. Density Functional Theory (DFT) calculation showed that chromium incorporation effectively shifts the d‐band centers (ɛd
) closer to the Fermi level and narrows the metal‐d/boron‐p band center gap (Δɛd‐p
) (Ni2B 1.10 eV → FeNiB 0.71 eV → Cr─FeNiB 0.55 eV) ultimately enhancing OER activity. Accordingly, the Δɛd‐p
is established as a key electronic descriptor for predicting and optimizing OER performance. These findings pave the way for a better understanding of metal boride‐derived electrocatalysts and also contribute to the development of efficient, stable, earth‐abundant, non‐noble metal catalysts for water oxidation.

A rational design of a highly efficient and stable oxygen evolution reaction (OER) electrocatalyst is achieved by microenvironmental modification of nickel‐boride active sites using cations, synthesized via a scalable one‐pot method. Comprehensive microscopy and spectroscopic characterization consistent with Density Functional Theory (DFT) simulations reveals chemical reconstruction toward a stable metal boride iron‐triad phase that enhances OER kinetics, producessynergistic effects, and provides insights for the development of advanced non‐noble metal‐based electrocatalysts.