Exploring the pathway to cleaner energy

By : Michael Gibb

Two efficient and inexpensive novel electrocatalysts for hydrogen production have been developed by a team co-led by CityU materials scientists. Hydrogen is a clean and sustainable alternative to fossil fuels, but producing low-cost, high-performance hydrogen evolution catalysts is problematic because expensive precious metals are required for their production.

A promising type of HER electrocatalyst is the single-atom catalyst because of its high activity, maximised atomic efficiency, and minimised catalyst usage. But fabricating these single-atom catalysts is complicated and requires a lot of energy and time.

Professor Lu Jian (seated, far left), Dr Li Yangyang (3rd from right) and the team have developed an electrocatalyst based on two-dimensional mineral gel nanosheets for hydrogen production. However, CityU’s new electrocatalysts offer some hope. They are based on two-dimensional mineral gel nanosheets and do not contain any precious metals, can be produced on a large scale and can help lower hydrogen prices.

“We found that mineral hydrogels have a great advantage for the mass production of electrocatalysts owing to the easy availability of the raw materials, a simple, environmentally friendly synthetic procedure, and mild reaction conditions,” says Professor Lu Jian, Director of the Hong Kong Branch of the National Precious Metals Material Engineering Research Center, Chair Professor in the Department of Mechanical Engineering and the Department of Materials Science and Engineering at CityU, who leads this research.

The results, published in Nature Communications, show that the new catalyst exhibits excellent electrocatalytic activity, long-term durability and ultra-stability.

The electrocatalyst has a dual-phase nanostructure. Another breakthrough by Professor Lu’s team is a new type of hydrogen evolution catalyst, the research for which was published in Science Advances.

The design strategy for the research provides an efficient route for the development of electrocatalysts for use in large-scale hydrogen production.

“Using a simple method called magnetron co-sputtering, my research team has produced a high-performance, low-cost substitute for platinum-based electrocatalysts,” says Professor Lu.

BiVO4 is a metal oxide semiconductor and a top-performing photocatalyst for the photoelectrochemical (PEC) water-splitting process, which generates hydrogen as a form of alternative energy. More exciting news for cleaner energy and carbon neutrality involves using metal oxides as a catalyst for photoelectrochemical (PEC) water splitting to produce hydrogen. The problem has been that the poor charge carrier transport impedes activity, particularly at low-bias voltage. But a team led by scholars from CityU, Australia and Germany has mediated this issue by adding phosphorus to a metal oxide catalyst, which reduces energy losses.

Key to the research, co-led by Professor Ng Yun-hau of CityU’s School of Energy and Environment (SEE) and published in Nature Communications, is BiVO4, a metal oxide semiconductor and a top-performing photocatalyst for PEC water-splitting process.

Professor Ng Yun-hau (right) and his research team member, Dr Wu Hao. “In the PEC water-splitting process, hydrogen and oxygen are produced from water, using sunlight and specialised semiconductors as photocatalysts, such as BiVO4. With light energy and an additional small voltage supply, the photocatalysts directly dissociate water molecules into hydrogen and oxygen,” explains Dr Ng, an expert in PEC research. “However, if the voltage supply is too low, a large fraction of the photo-excited charge carriers cannot be extracted efficiently.”

However, the team has found that by modifying the BiVO4 photoanodes, which help conserve energy, by adding phosphorus, the charge mobility is higher and can greatly increase the charge separation efficiency.

“We hope the mechanistic understanding of the enhancement of BiVO4; properties will offer a potential option for efficient hydrogen production to help achieve carbon neutrality,” adds Professor Ng.

Meanwhile, the International Conference on Clean Energy for Carbon Neutrality 2023 (ICCECN-2023) held at CityU in March stressed the urgent need to transition to decarbonised, sustainable energy systems. Led by the Hong Kong Institute for Clean Energy based at CityU and the French Academy of Sciences, the conference covered scalable photovoltaics, stable and reliable battery technologies, and energy-saving smart grid technologies. Discussions centred on energy generation, utilisation, storage, and distribution plus carbon capture and zero-carbon nuclear energy.

Professor Alex Jen shared his insights at the conference.“Combining the unique knowledge and experience of both HKICE and the Academy, ICCECN-2023 united world-renowned scholars and researchers in promoting interdisciplinary dialogue for scaling up clean energy, establishing clear targets, creating an enabling regulatory environment, and accelerating the adoption of emerging technology,” says Professor Alex Jen Kwan-yue, Director of HKICE and Lee Shau Kee Chair Professor of Materials Science at CityU.

Specific areas included the latest functional materials design and synthesis and smart device configuration for solar energy harvesting devices, rechargeable batteries, and energy-saving devices and applications as well as exploring fundamental principles and degradation mechanisms of energy devices that pose a limit on the large-scale, industrial applications of clean energy; among others.

“We hope the conference has enhanced research collaborations between CityU, the Academy and universities worldwide,” says Professor Jen.

This combination of CityU forums, scholarly research and international gathering are inspiring a more creative pathway to carbon neutrality.

World-renowned scholars and researchers gather at the conference to discuss clean energy issue.