Back to search

NANO2021-Nanoteknologi og nye materiale

A highly efficient and stable electrode for solar-driven water electrolysis, interrogated by advanced operando and in situ techniques

Alternative title: En høy-effektiv og stabil elektrode for soldrevet vannelektrolyse, studert med avanserte operando- og in-situ-teknikker

Awarded: NOK 12.0 mill.

Solar-powered water splitting is an elegant way of storing nature's alternating sunlight in the form of chemical bonds, in this case as renewable hydrogen gas. A key component in a light-driven water electrolysis cell is the anode electrode, which must be activated by sunlight and simultaneously release oxygen gas by oxidizing water. The other electrode, the cathode, is responsible for releasing hydrogen gas by reducing water. The primary losses in such photoelectrochemical (PEC) cells come from the anode electrode, as the oxygen evolution reaction is a complicated four-electron reaction, and furthermore, the oxidation conditions under the anode electrode materials degrade. In SolOPP, we study and develop a Ta3N5 photoanode. This material is one of the most efficient materials for PEC cells, but the material also breaks down in contact with water. To increase durability, we have surface-modified the Ta3N5 material. To see if this has worked, we have done synchrotron experiments at Lund in Sweden and in-situ measurements at DTU in Denmark. There we have studied the material properties of the Ta3N5 photoanode when in contact with water and light exposure. These experiments resemble the conditions the materials will be exposed to when used in an application. We have found that if we put a thin layer of nickel oxide on the Ta3N5 photoanode, the material will be much more stable. We have therefore gained insight and extracted important knowledge that can be used to further develop a more stable photoanode material.

The intermittent nature of sunlight necessitates the storage of the solar energy into chemical bonds. Renewable hydrogen fuel from solar-driven water splitting is a goal of great significance, as it will provide a predictable, carbon-neutral, and high-energy density fuel. Photoelectrochemical (PEC) water splitting is an elegant way for solar water electrolysis and hydrogen production, as the light absorbers are also the water electrolyzing electrodes, i.e. photoelectrodes. A good photoelectrode material must possess high water splitting efficiency and exceptional stability against photocorrosion. The goal behind SolOPP is to produce a Ta3N5-based photoelectrode with improved stability above the limit of at least 8 mA/cm2 set by the EU and US Energy Departments for commercial exploitation. This will be an unprecedented achievement within the field, and a significant step towards bringing photoelectrochemical (PEC) water electrolysis to a commercial level. Photocurrent densities almost as high as the theoretical limit of Ta3N5 has recently been achieved within the project consortium, but stability remains a major challenge. In SolOPP, we will develop innovative approaches to improve the stability, based on application of co-catalysts and protective coatings with closely tailored properties. The development will be aided by operando studies of the semiconductor/electrolyte interface using (near)-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), combined with in situ transmission microscopy (TEM) and theoretical calculations. The ambition of the project is to establish a complimentary framework for knowledge-based electrode development, all the way from state-of-the-art fundamental science to working PEC cell, combining expertise in photochemistry, semiconductors physics, advance characterization techniques, nanotechnology and theoretical modeling, in order to address important technological challenges that can form a sustainable future energy landscape.

Funding scheme:

NANO2021-Nanoteknologi og nye materiale