[Chinese Mainland] A team from Sichuan University of Science & Engineering proposes a new "electrochemical conversion" pathway for high-salinity concentrated brine: CoFeCe-Se multiphase heterostructure catalyst requires only 217 mV overpotential at 10 mA/

A large amount of high-salinity concentrated brine generated after advanced treatment of high-salinity wastewater is the toughest segment in the "near-zero discharge" chain. The Green Chemical Engineering and Waste Resource Utilization Innovation Team of Sichuan University of Science & Engineering proposes using high-salinity water for electrocatalytic water splitting to achieve synergistic utilization of water resources and hydrogen energy. To address the core challenges of competitive chlorine evolution reaction induced by high-concentration Cl⁻ and catalyst corrosion deactivation, the team adopts an anion-regulated phase evolution strategy to construct a CoFeCe-Se multiphase heterostructure catalyst—achieving 10 m A·cm⁻² current density at only 217 m V overpotential in alkaline seawater, while demonstrating excellent operational stability.

Problem: Why Is the Final Segment of Zero Liquid Discharge the Hardest

The mainstream zero liquid discharge process route for high-salinity wastewater (desulfurization wastewater, coal chemical wastewater, mine water, coking wastewater, electronic wastewater, etc.) typically follows "pretreatment—membrane concentration—evaporative crystallization." The membrane concentration unit is limited by operating pressure, resulting in a finite concentration limit. A large volume of concentrated brine is ultimately pushed to the terminal evaporative crystallization unit, leading to high investment and operating costs, short membrane element lifespan, and significant safety risks.

Even so, evaporative crystallization still produces high-salinity concentrated brine and mixed salts that are difficult to further reduce. The traditional approach treats this concentrated brine as an "end-of-pipe disposal" target, following solidification, landfill, or stockpiling routes. The alternative pathway proposed by the team is: since it cannot be reduced, it might as well be turned into a feedstock—using high-salinity water for electrocatalytic water splitting to simultaneously produce hydrogen energy, transforming a disposal cost center into an energy and resource node.

Obstacle: Chloride Ions Are the "Natural Enemy" of Catalysts

The concept is sound, but the engineering reality is quite harsh. High-concentration Cl⁻ brings threefold problems:

• Competitive chlorine evolution reaction—competing with the oxygen evolution reaction (OER) at the anode, reducing target reaction efficiency and producing chlorine gas and other by-products;
• Catalyst corrosion and dissolution—chloride ions have strong erosive effects on metal active sites, causing structural destruction of the catalyst;
• Activity decay—the superposition of the above processes causes catalyst lifespan to be far shorter than that in freshwater systems.

These three factors together have long confined "high-salinity water electrolysis" to the laboratory concept stage.

Solution: Anion-Regulated Phase Evolution to Construct Multiphase Heterostructures

The strategy adopted by the team is anion-regulated phase evolution: based on CoFeCe precursors, the structural evolution pathways are regulated through sulfidation, phosphidation, and selenization, respectively. Among these, the selenization process forms a multiphase heterostructure composed of CoSe₂, CoFe₂O₄, CeO₂, and residual CoFe-LDH, achieving synergistic enhancement of conductivity, interfacial activity, and structural stability.

Key conclusions regarding performance and mechanisms include:

• Activity metrics—in alkaline seawater, the CoFeCe-Se catalyst achieves 10 m A·cm⁻² current density at only 217 m V overpotential, and demonstrates excellent operational stability;
• Chlorine resistance mechanism—the multiphase heterostructure can effectively mitigate the erosion of high-concentration Cl⁻ on catalytic active sites and suppress the competitive chlorine evolution reaction;
• Charge transfer mechanism—electronic coupling between multiphase interfaces and the Ce³⁺/Ce⁴⁺ dynamic redox process together maintain efficient charge transfer in high-chloride environments;
• Design paradigm—the research provides a new catalyst design strategy for electrochemical conversion of high-salinity water from three aspects: chlorine corrosion resistance, chlorine evolution suppression, and oxygen evolution enhancement.

The related findings were published in the Journal of Physics and Chemistry of Solids (DOI: 10.1016/j.jpcs.2026.114032), with Professor Liu Xiaonan and Dr. Wang Lan as corresponding authors and Huang Kai as first author. Another work by the same team focuses on a multi-energy-field synergistic catalytic system, providing material and mechanistic foundations for addressing issues such as high external oxidant costs and significant interference from complex ions in high-salinity wastewater (published in Langmuir, DOI: 10.1021/acs.langmuir.6c03748). This series of studies was funded by the Sichuan Provincial Science and Technology Program, the "Yandu Hundred-Thousand-Ten Thousand Talent Program" Innovation Team, and the university's Research Innovation Team and Talent Introduction Projects.

Industry Implications: The Route Debate from "Reduction" to "Conversion"

What needs to be viewed soberly is that such results are still at the laboratory stage and remain some distance from engineering application. However, the changes in the technical route they point to deserve industry attention:

• Concentrated brine is no longer purely a burden — if high-salinity concentrated water can be used for hydrogen production by electrolysis, the economic model of Zero Liquid Discharge / ZLD processes will shift from "whole-process cost" to "output at the end";
• Naturally coupled with green hydrogen scenarios — the demand for green hydrogen in Industrial Parks and new energy bases highly overlaps geographically with the need for high-salinity wastewater disposal, providing implementation scenarios for "wastewater–hydrogen energy" synergy;
• Chlorine corrosion-resistant materials are a common bottleneck — the design strategy of this research does not only serve hydrogen production by electrolysis; it also has reference value for the selection of electrodes, membranes, and equipment materials under high-salinity systems.

What It Means for Us: TIANYI TECH's Judgment

TIANYI TECH has long served municipal and Industrial Park wastewater treatment and Reclaimed Water Reuse clients. Our judgment is: the technological competition in Zero Liquid Discharge / ZLD is shifting from "concentration ratio" to "outlet for concentrated water". The front-end membrane concentration process is already relatively mature. What truly determines project economics is how the terminal concentrated water and mixed salts are handled and whether they can be resource-recovered.

There are three practical recommendations for clients: First, plan the destination of concentrated water simultaneously at the process selection stage, avoiding the passive situation of "first producing concentrated water, then scrambling to find an outlet"; Second, prioritize salt separation and resource recovery pathways, diverting reusable industrial salts from mixed salts to reduce the terminal disposal volume; Third, for Industrial Parks with conditions for new energy consumption, incorporate "wastewater–hydrogen energy" synergy into medium- and long-term technical reserves, and track the engineering progress of chlorine corrosion-resistant electrodes and electrolysis materials.

For us, the significance of such frontier research lies in indicating direction rather than being immediately applicable. What truly needs to be done is to solidly implement the process combination of "quality-based pretreatment + high-efficiency membrane concentration + resource recovery of concentrated water," so that clients have the interface capability for seamless integration when new technologies mature.

About TIANYI LIMITED: TIANYI LIMITED is deeply engaged in the field of wastewater treatment and Reclaimed Water Reuse, committed to providing efficient, low-carbon, and sustainable water treatment solutions for municipal and industrial clients.