STUDY OF HYDROGEN EVOLUTION REACTION ACTIVITY ON PRISTINE AND POINT DEFECT SURFACE ACTIVE SITES OF NICKEL PHOSPATE

• Main Author: Puspasari Wijayanti, Dyah
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86792
• Institution: Institut Teknologi Bandung

The hydrogen gas produced by the hydrogen evolution reaction (HER) in water electrolysis offers a promising alternative to address the depletion of fossil fuel resources while advancing green energy initiatives for a cleaner environment. Currently, materials used as electrodes in water electrolysis include platinum (Pt), ruthenium (Ru), and iridium (Ir). However, these materials are precious metals are expensive, limiting their practically for large-scale industrial applications. As a result, nickel-based materials have gained attention as cost-effective alternative catalyst for water electrolysis systems. This research aims to explore the potential of nickel phosphate (Ni3(PO4)2, referred to as NiPO) as a HER catalyst using density functional theory (DFT) and the computational hydrogen electrode (CHE) approach. The study evaluates five of the most stable NiPO surfaces with the lowest surface energies, as analyzed by Nuruzzahran et al. focusing on both pure surfaces and surfaces with point defects such as oxygen and nickel vacancies. Defect models are considered because, in real-world conditions, obtaining pristine materials is highly challenging. The evaluation results show that the NiPO (100) and (011) surfaces have the best limitting potentials for HER. Through Gibbs free energy profile analysis and limitting potential evaluation, this research finds that the NiPO (100) surface with oxygen vacancy defects exhibits the best HER activity. These findings align with catalytic patterns indicating that more stable surfaces tend to have lower adsorption energies, which is beneficial for the HER process. Computational calculations using DFT show results consistent with experiments by Mehdi et al. where NiPO is not yet as efficient as platinum, but it is still more efficient than pristine nickel. This provides new insights into designing NiPO-based HER catalysts, particularly surface engineering and oxygen vacancy formation for optimal catalytic performance. Keywords: NiPO, water electrolysis, catalyst, limitting potential, Gibbs free energy, DFT