World Earth Day | Tsinghua University Shenzhen International Graduate School: Harnessing the Potential of “New Materials” for a Sustainable Future

April 22, 2025, marks the 56th celebration of World Earth Day. This year’s theme, “Our Power, Our Planet,” reignites humanity’s deep commitment to protecting the Earth and actively seeking solutions. As we commemorate the 56th anniversary of Earth Day, it is essential to reflect on whether we have found answers for coexisting with our planet, especially as “carbon neutrality” becomes a global consensus and “clean energy” is integrated into the United Nations Sustainable Development Goals.

At the forefront of technological innovation, the Tsinghua University Shenzhen International Graduate School (referred to as Tsinghua SIGS) leads a research team within its Materials Research Institute, focusing on the development of new materials and renewable energy. With a commitment to a “top-down and bottom-up” research philosophy, the team is dedicated to advancing energy materials and devices, low-dimensional materials and devices, as well as biomedical materials and devices.

The research initiatives range from transforming industrial wastewater into valuable resources to reviving retired batteries. Innovations also include efficiently converting sunlight into electricity and scaling up green hydrogen production. From precise water pollution control to developing environmentally friendly antibacterial materials, the researchers at Tsinghua SIGS are committed to using innovative technology to protect the Earth’s ecosystem, providing “Tsinghua solutions” for sustainable development.

On this Earth Day, let us focus on the innovative breakthroughs in materials science at Tsinghua SIGS and explore how they harness the power of “new materials” and “new energy” to empower sustainable development and protect our blue planet.

Transforming Wastewater into Ammonia: A “Magical Revolution” in Industrial Wastewater Treatment

As industrial manufacturing accelerates, high-concentration nitrate wastewater from photovoltaic manufacturing and nuclear industries poses significant environmental challenges. To turn this hazardous waste into ammonia, Professor Liu Biluo’s team has developed a large-current nitrate wastewater-to-ammonia technology using electrochemical nitrate reduction (NO3RR). This method achieves both “wastewater treatment” and “resource recovery.”

The team’s self-developed copper nanosheets catalyst can convert nitrate pollutants in wastewater into ammonia and high-value chemicals at room temperature and pressure. Furthermore, the modular photovoltaic-driven ammonia production system integrates photovoltaic power, wastewater pretreatment, membrane electrode stacks, and ammonia recovery systems. Within an hour, it can reduce nitrate concentration by three orders of magnitude and recover grams of ammonium chloride, paving the way for sustainable nitrogen resource cycling and offering new paradigms for ecological restoration and high-value chemical synthesis.

Injecting “Green Energy” into Battery Recycling

With the explosive growth of the renewable energy industry, the usage and disposal of lithium batteries are increasing daily. Facing the projected 3.5 million tons of retired batteries in China by 2030, Associate Professor Zhou Guangmin’s team has pioneered direct recycling technology that revolutionizes traditional methods. This technology transforms waste into treasure by precisely repairing failed cathode materials, significantly improving recovery rates while avoiding the use of strong acids and bases.

Currently, the team is establishing a pilot facility in Longgang District, Shenzhen, with a demonstration line capable of processing 10 tons annually. The performance of the recovered products is comparable to commercial materials, allowing important resources like lithium and cobalt to be reborn and injecting “green energy” into the battery industry.

Creating Clean Energy “Harvesting Stations”

As the renewable energy and electronics sectors evolve rapidly, the demand for high-performance energy conversion devices has grown. When traditional photovoltaic systems face rigid limitations, Associate Professor Wei Guodan’s team focuses on developing solar cell materials and devices to enhance the conversion of solar energy into clean electrical energy, enabling buildings to generate their own power.

Focusing on the development of third-generation photovoltaic materials, the team has achieved breakthroughs in new perovskite and organic semiconductor thin-film solar cells. Using their self-developed “chemical bond management technology,” they have increased the power conversion efficiency of the newly developed thin-film solar cells to 25.4% (laboratory data), maintaining 90% of the initial power conversion efficiency after over 350 hours of continuous illumination. This innovation is poised to break through the industrialization bottleneck of this technology pathway.

Moreover, the new thin-film solar cells are redefining the boundaries of traditional silicon-based photovoltaics, transforming bulky photovoltaic devices into “invisible power-generating layers” on glass facades, tent materials, and even smartphone screens.

Unlocking the Future with Green Hydrogen Technology

Amid the transition to a sustainable energy ecosystem, green hydrogen has emerged as a key pathway to achieving carbon neutrality. Electrolysis of water for hydrogen production is considered the core method for large-scale green hydrogen production due to its efficiency and cleanliness. However, challenges like bubble interference and catalyst deactivation at high current densities have long hindered electrolysis technology.

Inspired by the leaves of ferns, Associate Professor Yang Cheng’s team has developed biomimetic electrodes with a graded ordered structure, significantly enhancing both catalytic performance and stability under high current densities. This innovation provides a universal solution for bubble management in multiphase catalytic systems, thereby advancing the development of hydrogen production and other renewable energy conversion technologies.

Ensuring Water Safety with Antibacterial Materials

How can we endow atomically thin two-dimensional materials with broad-spectrum antibacterial properties? Associate Professor Lei Lu’s team has taken a unique approach by utilizing active defects in boron nitride to create a “nanoblade” material that can physically cut bacterial membranes and disrupt electron transfer. This material achieves a 99.99% kill rate against pathogens like E. coli while exhibiting low toxicity to normal cells. Its stable dispersion in water makes it suitable for wastewater treatment and medical device coatings, reducing bacterial pollution in water bodies and contributing to water safety.

Gathering Talent to Build a Leading Research Hub

By 2024, Tsinghua SIGS will have added three new disciplines to the top 1% of ESI rankings, with materials science reaching the top 1.22‰. Notably, among the 40 full-time faculty members in the Materials Research Institute, eight have been recognized as Highly Cited Researchers by Clarivate Analytics in 2024. This includes faculty members such as He Yanbing, Kang Feiyu, Li Baohua, Liu Biluo, Lü Wei, Peng Lele, Zhou Guangmin, and Zou Xiaolong.

Research at Tsinghua SIGS extends beyond laboratory breakthroughs to talent cultivation and social service. Through forums featuring outstanding students and young scholars, the graduate school fosters academic collaboration, encouraging mutual growth and the development of new energy materials.

Creating an International Academic Exchange Platform

Tsinghua SIGS aims to establish a world-class training base for materials research talent and scientific advancements. The Materials Research Institute is committed to talent development, hosting high-level international conferences annually, including the Shenzhen Graphene International Forum and international symposiums on energy storage materials. These events gather leading scholars from around the globe to ignite creativity in the materials field.

In collaboration with renowned research teams and companies, the Materials Research Institute shares resources with advanced battery industries and research teams in the Shenzhen area, promoting the transformation of scientific research achievements into practical applications.

Tsinghua University Shenzhen International Graduate School interprets “Our Power” through the strength of materials. On this Earth Day, we call for attention to clean energy technologies, the practice of resource recycling concepts, and participation in the dissemination of green technologies to build a sustainable future for our planet together.

New horizons await! This international academic event is driving a revolution in the two-dimensional materials industry, with academicians leading discussions on the frontiers of new energy and materials at Tsinghua SIGS!