Diatom derived hollow 3D Frame as a synergetic support for millerite nanoparticles: A unique hydrogen evolution electrocatalyst and its mechanistic insights

Abstract

The embedding of metal nanoparticles (NPs) on/into porous supports, including alumina, zeolites, and porous carbon materials, has recently been widely studied to develop advanced catalysts for various energy-related applications. Unlike conventional support materials, diatoms (i.e., Bacillariophyceae), naturally available aluminosilicate materials with a hollow, three-dimensional (3D) porous, durable structure, provide unique opportunities as a support material of metal nanoparticle catalysts for energy-related catalytic applications. Here, we developed an environmentally benign diatom/NiS (Millerite (NiS)) hetero-catalyst for electrocatalytic application. The prepared hetero-composite material was characterized using various analytical methods to understand the structural features and the chemical nature. The diatom/NiS nanocatalyst demonstrated remarkable hydrogen evolution reaction (HER) activity, achieving a low overpotential (53.6 mV) and Tafel slope (55.1 mV dec-1) in sulfuric acid (0.50 M) at-10 mA cm- 2 current density comparable to the commercial noble metal catalyst (Pt/C), which was significantly enhanced than pure NiS. The product (H2) analysis proved the quantitative Faradaic efficiency (99.74 %). The results of the density functional theory (DFT) calculations allow a fundamental understanding of the unique catalytic activity of the material. The DFT calculation results revealed that embedding NiS nanoparticles in diatoms generated effective active sites, resulting in the low Delta GH* (-0.05 eV) for the diatom/NiS heterostructure. Further experiments proved that the heterostructure showed a catalytic activity in oxygen evolution reaction (OER) in a basic medium. This work presents the unique cooperative catalytic behavior of diatom-supported NiS nanoparticle heterostructure, and the proposed strategy can represent the development of a noble eco-friendly electrocatalyst for energy conversion and harvesting.