Semiconductor nanostructures for water-splitting application

Abstract

Water-splitting reaction is one ideal and clear method for oxygen hydrogen production, and it is important to develop effective, stable and earth-abundant catalyst for the reaction. Water is required for the reaction with the help of electrocatalyst. The half reactions including oxygen evolution reaction (OER) of water-splitting reaction was being studied in this paper. OER is a four electrons-transfer reaction, slower and easier to control and observation. OER was chosen to be studied in this paper instead of HER to understand how much energy is required to put in the system, for an overall understanding of water-splitting reaction. A ideal catalyst for water-splitting reaction should have a hydrogen binding free energy (∆GH) closest to zero, such as the noble metal such as Platinum (Pt). However, Pt is too expensive for urban usage. Therefore, materials researchers are working on finding a non-noble catalyst for water-splitting reaction. For metal catalyst, an important parameter to indicated the catalysis efficiency is called overpotential, the smaller the overpotential is preferred. Overpotential of the samples is discussed. Metal element Nickel (Ni) is one of the focus of metal catalyst. In this research, semiconductor Boron is used to combine with Nickel as to study the effect by altering Nickel 's properties. The fabrication techniques are also being studied in this paper. The formation of Ni-B is done by alternative dipping process of precursor and reducing agent. The effect of the dipping cycles on the catalyst performance is concerned. Moreover, hierarchical nanostructure is al so studies in this paper. This is a perfect structure for catalyst due to its large surface area to volume ratio. A Ni(OH)2 hierarchical nanostructure is synthesized on Nickel foam and experimented in this research. The Ni-B particles is loaded on the hierarchical nanostructure. A non-noble metal catalyst Ni-B load on Ni(OH)z hierarchical nanostructure is going to be studied in this paper. Material characterizations is carried out after synthesis of samples, electrochemical measurement was carried out and the value of overpotential of the samples is obtained. The Ni-B @ Ni(OH)2 @ Ni foam with 3 dipping cycles has a stable and high electrocatalytic activity towards OER in alkaline condition, to produce 100 rnA cm-2 at overpotential of 314 mV in electrolyte KOH 1M with pH 13.67. Indicating that the combination of Ni-B and hierarchical nanostructure results to a high catalytic activity and cost-effective electrocatalyst for water-splitting reaction. Working mechanism, involved materials and the fabricate techniques such as dipping deposition cycle of Ni-B are also studied in this paper.