Experimental and Computational Insights into the Overall Water Splitting Reaction by the Fe-Co-Ni-P Electrocatalyst

Lakshya Kumar; Bindu Antil; Ankur Kumar; Manash R Das; Omar López-Estrada; Samira Siahrostami; Sasanka Deka

doi:10.1021/acsami.3c11947

Experimental and Computational Insights into the Overall Water Splitting Reaction by the Fe-Co-Ni-P Electrocatalyst

ACS Appl Mater Interfaces. 2023 Nov 29;15(47):54446-54457. doi: 10.1021/acsami.3c11947. Epub 2023 Nov 16.

Authors

Lakshya Kumar¹, Bindu Antil¹, Ankur Kumar¹, Manash R Das², Omar López-Estrada³, Samira Siahrostami⁴, Sasanka Deka¹

Affiliations

¹ Nanochemistry Laboratory, Department of Chemistry, University of Delhi, North campus, Delhi 110007, India.
² Advanced Materials Group, Materials Sciences and Technology Division, CSIR-North East Institute of Science and Technology, Jorhat 785006, Assam, India.
³ Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
⁴ Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.

PMID: 37970629
DOI: 10.1021/acsami.3c11947

Abstract

Nonprecious transition-metal phosphides (TMPs) are versatile materials with tunable electronic and structural properties that could be promising as catalysts for energy conversion applications. Despite the facts, TMPs are not explored thoroughly to understand the chemistry behind their rich catalytic properties for the water splitting reaction. Herein, spiky ball-shaped monodispersed TMP nanoparticles composed of Fe, Co, and Ni are developed and used as efficient electrocatalysts for hydrogen and oxygen evolution reaction (HER, OER), and overall water splitting in alkaline medium; and their surface chemistry was explored to understand the reaction mechanism. The optimized Fe_0.5CoNi_0.5P catalyst shows attractive activities of HER and OER with low overpotentials and Tafel slopes, and with high mass activities, turnover frequencies, and exchange current densities. When applied to overall water splitting, the electrolyzer Fe_0.5CoNi_0.5P||Fe_0.5CoNi_0.5P cell can reach a 10 mA cm^-2 current density at cell voltages of only 1.52 and 1.56 V in 1.0 M and 30 wt % KOH, respectively, much lower than those of commercial IrO₂||Pt/C. The optimized electrolyzer with sizable numbers of chemically active sites exhibits superior durability up to 70 h and 5000 cycles in 1.0 M KOH and can attain a current density as high as 1000 mA cm^-2, showing a class of efficient bifunctional electrocatalysis. Experimental and density functional theory-based mechanistic analyses reveal that surface reconstruction takes place in the presence of KOH to form the TMP precatalyst, which results in high coverage of oxygen active species for the OER with a low apparent activation energy (E_a) for conversion of *OOH to O₂. These also evidenced the thermoneutral adsorption of H* for the efficient HER half-reaction.

Keywords: FeCoNiP nanoparticle; density functional theory; electrocatalyst; hydrogen evolution reaction; overall water splitting; oxygen evolution reaction.