A cyclic flow process for optimizing electrocatalytic reduction of nitrate to ammonia by pecvd
By coupling the PECVD equipment with the electrocatalytic nitrate reduction process, oxygen and nitrogen are recycled to generate active particles, solving the problems of insufficient catalyst activity and hydrogen evolution side reactions, and achieving efficient ammonia production and low-cost operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUANENG POWER INT INC YINGKOU POWER PLANT
- Filing Date
- 2026-03-12
- Publication Date
- 2026-06-05
AI Technical Summary
Existing electrocatalytic nitrate reduction technology suffers from insufficient catalyst activity and severe hydrogen evolution side reactions at low nitrate concentrations, resulting in low ammonia yield and selectivity, as well as high operating costs, making it difficult to scale up.
By coupling the PECVD equipment with the electrocatalytic nitrate reduction process, the oxygen generated at the anode and the external nitrogen are recycled to generate active particles that promote the nitrate reduction reaction. Combined with gas circulation design and catalyst regeneration, process parameters are optimized to improve reaction efficiency and stability.
It significantly improved ammonia yield and selectivity, reduced raw material consumption and waste gas treatment costs, and enhanced the stability and sustainability of the system.
Smart Images
Figure CN122147354A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of energy recovery technology, specifically to a cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization. Background Technology
[0002] Electrocatalytic nitrate reduction technology, as a green technology capable of simultaneously treating wastewater and synthesizing clean ammonia, has received widespread attention in recent years. This technology utilizes electrical energy to reduce nitrate ions to ammonia under mild conditions, offering the dual advantages of environmental remediation and resource recovery.
[0003] However, existing technologies still face significant bottlenecks in industrial applications, primarily manifested in insufficient catalyst activity at low nitrate concentrations, severe hydrogen evolution side reactions leading to low ammonia yield and selectivity, difficulty in continuously improving reaction efficiency, and high operating costs. Particularly in continuous flow systems, the unutilized gaseous byproducts and energy losses further constrain the large-scale promotion of this technology.
[0004] Therefore, this application proposes a cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization. Summary of the Invention
[0005] Therefore, this invention provides a cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization, in order to solve the problems in the prior art, such as insufficient activity of the chemical agent at low nitrate concentrations, severe hydrogen evolution side reactions leading to low ammonia yield and selectivity, difficulty in continuously improving reaction efficiency, and high operating costs.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization includes the following steps:
[0008] Step 1: Construct a closed-loop reaction system: Connect the large flow electrolysis cell, electrochemical workstation, nitrogen storage tank, gas mixing device and PECVD equipment through gas and electrical circuits to form a closed-loop reaction system;
[0009] Step 2, prepare and treat the electrolyte: inject an electrolyte containing nitrate ions into a large flow electrolytic cell and perform pre-aeration to remove dissolved oxygen;
[0010] Step 3: Perform the electrocatalytic nitrate reduction reaction: Start the electrochemical workstation to carry out the nitrate reduction reaction at the cathode of the large flow electrolyzer, while water oxidation occurs at the anode to generate oxygen.
[0011] Step 4, collecting and mixing anode gas: The oxygen generated at the anode is led out through a gas pipeline and mixed evenly with the nitrogen gas transported from the nitrogen storage tank in a gas mixing device to form an oxygen-nitrogen mixed gas.
[0012] Step 5, Plasma activation treatment: The oxygen-nitrogen mixed gas is introduced into the PECVD equipment, and ionized under the action of plasma to generate active particles containing nitrogen and oxygen;
[0013] Step 6, Active Particle Injection into Cathode: The active particles output from the PECVD equipment are introduced into the cathode region of the large flow electrolysis cell through a gas distribution device to promote the formation of intermediates in the nitrate reduction reaction.
[0014] Step 7, Reaction process monitoring and control: The reaction voltage, current and pH value are monitored in real time through an electrochemical workstation, and the gas flow rate and plasma power are adjusted according to the feedback;
[0015] Step 8, Product Collection and System Circulation: During the reaction, the generated ammonia gas is continuously collected, and the unreacted gas is separated and reintroduced into the gas mixing device to achieve gas recycling.
[0016] Preferably, the electrolyte is an aqueous solution containing at least one of sodium nitrate, potassium nitrate, or ammonium nitrate, wherein the nitrate ion concentration is 10-500 mmol / L, and a buffer and supporting electrolyte are added.
[0017] Preferably, the process parameters of the PECVD equipment include: radio frequency power of 50-500 W, working gas pressure of 10-200 Pa, gas flow rate of 10-200 sccm, and oxygen-nitrogen volume mixing ratio of 1:1 to 1:5.
[0018] Preferably, the active particles are injected into the cathode through a porous gas distributor or a microchannel array.
[0019] Preferably, the electrolyte has a nitrate ion concentration of 50-200 mmol / L, the buffer is a phosphate buffer system, and the pH value is controlled between 6 and 8.
[0020] Preferably, the plasma activation process of the oxygen-nitrogen mixed gas in the PECVD equipment is carried out under the conditions of radio frequency power of 100-300W and working gas pressure of 50-150 Pa, the gas mixing ratio is 1:2 to 1:4, and the activation time is 5-30 minutes; a graphite or metal carrier plate is provided in the plasma reaction chamber to enhance plasma uniformity; after activation, the gas is cooled to 40-60℃ by a cooling device before being introduced into the cathode area; the PECVD equipment is equipped with an in-situ spectral monitoring module to detect the type and concentration of active particles in real time, and dynamically adjust the radio frequency power and gas mixing ratio according to the detection results.
[0021] Preferably, the porous gas distributor is made of hydrophobic porous ceramic or polymer material with a pore size range of 10-100 micrometers. The gas distributor is disposed below or on the side of the cathode catalyst layer and is arranged perpendicular to the electrolyte flow direction.
[0022] Preferably, the process further includes step nine: after the reaction is completed, the electrolyte is subjected to solid-liquid separation to recover the suspended catalyst particles, and the surface is regenerated using a PECVD device. The regenerated catalyst is then reintroduced into the next reaction cycle.
[0023] The present invention has the following advantages: By introducing the coupling of PECVD equipment with the electrocatalytic nitrate reduction process, the present invention achieves effective activation and recycling of oxygen generated at the anode and external nitrogen, and the generated active particles significantly improve the cathode reduction reaction rate and ammonia yield; the present invention avoids direct oxygen emission through gas circulation design, reducing raw material consumption and waste gas treatment costs; moreover, the overall process improves reaction efficiency while enhancing the stability and sustainability of the system. Attached Figure Description
[0024] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).
[0025] Figure 1 A schematic diagram of a circulating process for the electrocatalytic reduction of nitrate to ammonia by PECVD, provided for embodiments of this application;
[0026] Figure 2 A flowchart illustrating the steps of a cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD, as provided in this application embodiment. Detailed Implementation
[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. It should be understood that these embodiments are merely for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Technical engineers in the field can make some non-essential improvements and adjustments to the present invention based on the above-described content. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Please see Figure 1 , 2 A cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization includes the following steps:
[0029] Step 1: Construct a closed-loop reaction system: Connect the large flow electrolysis cell, electrochemical workstation, nitrogen storage tank, gas mixing device and PECVD equipment through gas and electrical circuits to form a closed-loop reaction system;
[0030] Step 2, prepare and treat the electrolyte: inject an electrolyte containing nitrate ions into a large flow electrolytic cell, control the total volume of the electrolyte to 5L, and perform pre-aeration to remove dissolved oxygen;
[0031] Step 3: Perform electrocatalytic nitrate reduction reaction: Start the electrochemical workstation to carry out nitrate reduction reaction at the cathode of the large flow electrolytic cell. At the same time, water oxidation reaction occurs at the anode to generate oxygen. The oxygen generated by the anode water oxidation is not discharged, but is mixed with the supplemented nitrogen and introduced into the PECVD equipment. This recycling design eliminates the waste of oxygen and reduces the cost of raw material gas consumption.
[0032] Step 4, collecting and mixing anode gas: The oxygen generated at the anode is led out through a gas pipeline and mixed evenly with the nitrogen gas transported from the nitrogen storage tank in a gas mixing device to form an oxygen-nitrogen mixed gas.
[0033] Step 5, Plasma activation treatment: The oxygen-nitrogen mixed gas is introduced into the PECVD equipment and ionized under the action of plasma to generate active particles containing nitrogen and oxygen. In the PECVD chamber, the mixed gas is ionized under the action of plasma to generate highly active nitrogen and oxygen particles (such as excited-state N2, O, NOx, etc.). The plasma activation step generates active intermediates that are difficult to obtain in the traditional electrolysis process, providing a new and efficient pathway for subsequent reduction reactions.
[0034] Step 6, Active Particle Injection into Cathode: The active particles output from the PECVD equipment are introduced into the cathode region of the large flow electrolytic cell through a gas distribution device to promote the formation of intermediates in the nitrate reduction reaction. The active particles are directionally injected into the cathode region of the electrolytic cell to participate in and significantly accelerate the surface reaction kinetics of nitrate reduction, thereby increasing the ammonia generation rate and effectively suppressing side reactions such as hydrogen evolution, thus solving the pain point of low selectivity in existing technologies.
[0035] Step 7, Reaction process monitoring and control: The reaction voltage, current and pH value are monitored in real time through an electrochemical workstation, and the gas flow rate and plasma power are adjusted according to the feedback;
[0036] Step 8, Product Collection and System Circulation: During the reaction, the generated ammonia gas is continuously collected, and the unreacted gas is separated and reintroduced into the gas mixing device to achieve gas recycling.
[0037] The entire system is monitored and adjusted in real time via an electrochemical workstation, achieving dynamic matching of gas flow rate, plasma power, and reaction state. This intelligent control mechanism ensures stable operation of the system under optimal conditions, further reducing energy consumption and operating costs. Ultimately, unreacted reactive gases can be separated and re-entered into the circulation system, achieving efficient internal circulation of the reactant gases and significantly improving atom economy and the economic feasibility of the entire process.
[0038] The electrolyte is an aqueous solution containing at least one of sodium nitrate, potassium nitrate, or ammonium nitrate, wherein the nitrate ion concentration is 10-500 mmol / L, and a buffer and a supporting electrolyte are added. Nitrate ions are provided by nitrates, and the concentration range covers the treatment requirements from low-concentration wastewater to high-concentration feed solutions. The pH of the reaction system is maintained by adding a buffer, and the conductivity of the solution is improved by adding a supporting electrolyte, which together ensures that the reaction proceeds efficiently and stably.
[0039] The process parameters of the PECVD equipment include: radio frequency power of 50-500 W, working gas pressure of 10-200 Pa, gas flow rate of 10-200 sccm, and oxygen-nitrogen volume mixing ratio of 1:1 to 1:5, thereby ensuring that the mixed gas is efficiently and uniformly activated into target active particles, providing effective support for subsequent electrocatalytic reduction.
[0040] The active particles are injected into the cathode through a porous gas distributor or microchannel array to ensure uniform dispersion and efficient mass transfer of the active particles in the electrolyte. The use of a porous gas distributor or microchannel array achieves uniform and controllable delivery of the active particles, and this design also enhances the mass transfer efficiency at the gas-liquid-solid three-phase interface, improving the utilization rate of the active particles and the reaction rate.
[0041] The electrolyte contains nitrate ion concentrations of 50-200 mmol / L, uses a phosphate buffer system as the buffer, and maintains a pH value between 6 and 8.
[0042] The plasma activation process of the oxygen-nitrogen mixed gas in the PECVD equipment is carried out under the conditions of radio frequency power of 100-300 W and working gas pressure of 50-150 Pa, with a gas mixing ratio of 1:2 to 1:4 and an activation time of 5-30 minutes. A graphite or metal carrier plate is installed in the plasma reaction chamber to enhance plasma uniformity. After activation, the gas is cooled to 40-60°C by a cooling device before being introduced into the cathode area to avoid the adverse effects of high temperature on the electrocatalytic reaction. In addition, the PECVD equipment is equipped with an in-situ spectral monitoring module to detect the type and concentration of active particles in real time, and dynamically adjust the radio frequency power and gas mixing ratio according to the detection results to maintain the stability of active particle output and optimize reaction efficiency.
[0043] By real-time detection of the composition of active particles and automatic adjustment of process parameters, the stability and efficiency of the plasma activation process are ensured, thereby improving the controllability and long-term operational stability of the overall system.
[0044] The porous gas distributor is made of hydrophobic porous ceramic or polymer material with a pore size range of 10-100 micrometers. The gas distributor is set below or to the side of the cathode catalyst layer and arranged perpendicular to the electrolyte flow direction to enhance the gas-liquid-solid three-phase contact efficiency. The use of hydrophobic porous material can prevent electrolyte backflow. The micrometer-level pore size and cross-flow arrangement can enhance gas-liquid mixing and mass transfer, thereby significantly improving the efficiency of active particles on the cathode surface.
[0045] The process also includes step nine: after the reaction is complete, the electrolyte undergoes solid-liquid separation to recover the suspended catalyst particles, and then performs surface regeneration treatment using a PECVD device. The regenerated catalyst is then reintroduced into the next reaction cycle. Treating deactivated catalysts with PECVD plasma effectively restores their activity, enabling catalyst recycling and reducing operating costs.
[0046] Example 1
[0047] Implementation steps:
[0048] The first step is to set up the system: connect the large flow electrolyzer, electrochemical workstation, nitrogen storage tank, gas mixing device and PECVD equipment.
[0049] The second step is to prepare the electrolyte: add 5L of electrolyte containing 100 mmol / L sodium nitrate, 0.1 M phosphate buffer (pH=7.0) and 0.5 M sodium sulfate to the electrolytic cell, and pre-purify with nitrogen to remove oxygen.
[0050] The third step is to start the reaction: set the electrochemical workstation to a constant potential of -1.2 V (vs. RHE) and turn on the circulation pump to make the electrolyte flow.
[0051] The fourth step is gas mixing and activation: oxygen and nitrogen generated at the anode are mixed at a volume ratio of 1:3 and introduced into the PECVD equipment at a total flow rate of 100 sccm. The radio frequency power is set to 200 W and the working pressure to 100 Pa for plasma activation.
[0052] Step 5, inject active particles: inject the PECVD outlet gas into the cathode area through a porous ceramic distributor (50 μm pore size) installed at the bottom.
[0053] Step 6: Continue the reaction for 4 hours, monitor the current and pH in real time, and take samples every 30 minutes to test the ammonia concentration.
[0054] Results: The ammonia yield was 12.3 mg / h, the Faraday efficiency (FE) was 68%, the system operated stably and continuously without significant performance degradation.
[0055] Example 2
[0056] Based on Example 1, the following adjustments are made:
[0057] PECVD process parameters: RF power 250 W, gas pressure 80 Pa, oxygen-nitrogen mixing ratio 1:2.5.
[0058] The in-situ spectral monitoring module was activated to detect NO and N2 in the plasma in real time. + The emission peak intensity.
[0059] When the NO peak intensity drops by more than 10%, the nitrogen ratio is automatically adjusted to 1:2, and the power is slightly increased to 260 W.
[0060] The gas is cooled to 50°C and then injected into the cathode.
[0061] Results: Ammonia yield increased to 15.1 mg / h, FE increased to 75%, system fluctuations were smaller, and the output of active particles was stable.
[0062] Example 3
[0063] Implementation steps:
[0064] The system was run continuously for 24 hours under the same conditions as in Example 1.
[0065] The reaction was stopped, and the copper-based catalyst particles in the electrolyte were recovered by filtration.
[0066] The recovered catalyst was placed in a PECVD chamber and treated for 20 minutes at 80 W radio frequency power under an argon atmosphere containing 5% hydrogen.
[0067] The regenerated catalyst was reintroduced into the electrolytic cell, and the 4-hour reaction of Example 1 was repeated.
[0068] Results: After regeneration, the catalyst activity recovered to 92% of the initial level, the ammonia yield was 11.4 mg / h, and the FE was 65%, indicating that the catalyst can be effectively recycled.
[0069] Comparative Example 1
[0070] Implementation conditions:
[0071] Use the same electrolyte and electrolytic cell, but do not connect to the PECVD device.
[0072] The oxygen produced at the anode is directly released into the atmosphere, while only nitrogen is introduced into the cathode as a protective gas.
[0073] The remaining electrochemical conditions were the same as in Example 1.
[0074] Results: The ammonia yield was only 4.2 mg / h, the FE was 28%, and the current decreased significantly after 2 hours of reaction. Hydrogen evolution was accelerated on the catalyst surface.
[0075] Comparative Example 2
[0076] Implementation conditions:
[0077] Nitrogen gas is introduced into the cathode after PECVD activation, while oxygen is directly discharged from the anode.
[0078] The remaining conditions are the same as in Example 1.
[0079] Results: The ammonia yield was 7.8 mg / h and the FE was 45%, which was better than Comparative Example 1, but still significantly lower than Example 1, indicating that oxygen cycling and nitrogen co-activation have a synergistic enhancing effect.
[0080] Comparative Example 3
[0081] Implementation conditions:
[0082] The oxygen-nitrogen mixing ratio was changed to 1:10, the radio frequency power was set to 50 W, and the air pressure was set to 500 Pa.
[0083] The remaining conditions are the same as in Example 1.
[0084] Results: The ammonia yield was only 5.1 mg / h and the FE was 32%, indicating that the activation effect decreased significantly after the PECVD parameters deviated from the optimized range, and the system performance was close to that of the traditional method.
[0085] Comparative Example 4
[0086] Implementation conditions:
[0087] The PECVD outlet gas is directly bubbled into the bottom of the cathode through a single tube, without using a porous distributor.
[0088] The remaining conditions are the same as in Example 1.
[0089] Results: The ammonia yield was 9.0 mg / h, the FE was 52%, the bubbles were large and unevenly distributed, the mass transfer efficiency was low, and the active particles were not fully utilized.
[0090] The above examples and comparative examples demonstrate that the present invention significantly improves the yield, selectivity, and system stability of electrocatalytic nitrate reduction to ammonia by PECVD activation of the oxygen-nitrogen mixture and recycling of anode oxygen, combined with optimized process parameters, efficient gas distribution design, and catalyst regeneration, thus possessing clear advantages for industrial applications.
[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization, characterized in that, Includes the following steps: Step 1: Construct a closed-loop reaction system: Connect the large flow electrolysis cell, electrochemical workstation, nitrogen storage tank, gas mixing device and PECVD equipment through gas and electrical circuits to form a closed-loop reaction system; Step 2, prepare and treat the electrolyte: inject an electrolyte containing nitrate ions into a large flow electrolytic cell and perform pre-aeration to remove dissolved oxygen; Step 3: Perform the electrocatalytic nitrate reduction reaction: Start the electrochemical workstation to carry out the nitrate reduction reaction at the cathode of the large flow electrolyzer, while water oxidation occurs at the anode to generate oxygen. Step 4, collecting and mixing anode gas: The oxygen generated at the anode is led out through a gas pipeline and mixed evenly with the nitrogen gas transported from the nitrogen storage tank in a gas mixing device to form an oxygen-nitrogen mixed gas. Step 5, Plasma activation treatment: The oxygen-nitrogen mixed gas is introduced into the PECVD equipment, and ionized under the action of plasma to generate active particles containing nitrogen and oxygen; Step 6, Active Particle Injection into Cathode: The active particles output from the PECVD equipment are introduced into the cathode region of the large flow electrolysis cell through a gas distribution device to promote the formation of intermediates in the nitrate reduction reaction. Step 7, Reaction process monitoring and control: The reaction voltage, current and pH value are monitored in real time through an electrochemical workstation, and the gas flow rate and plasma power are adjusted according to the feedback; Step 8, Product Collection and System Circulation: During the reaction, the generated ammonia gas is continuously collected, and the unreacted gas is separated and reintroduced into the gas mixing device to achieve gas recycling.
2. The cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization according to claim 1, characterized in that, The electrolyte is an aqueous solution containing at least one of sodium nitrate, potassium nitrate, or ammonium nitrate, wherein the nitrate ion concentration is 10-500 mmol / L, and a buffer and supporting electrolyte are added.
3. The cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization according to claim 1, characterized in that, The process parameters of the PECVD equipment include: radio frequency power of 50-500 W, working gas pressure of 10-200 Pa, gas flow rate of 10-200 sccm, and oxygen-nitrogen volume mixing ratio of 1:1 to 1:
5.
4. The cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization according to claim 1, characterized in that, The active particles are injected into the cathode through a porous gas distributor or a microchannel array.
5. The cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization according to claim 2, characterized in that, The electrolyte contains nitrate ion concentrations of 50-200 mmol / L, uses a phosphate buffer system as the buffer, and maintains a pH value between 6 and 8.
6. The cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization according to claim 3, characterized in that, The plasma activation process of the oxygen-nitrogen mixed gas in the PECVD equipment is carried out under the conditions of radio frequency power of 100-300W and working gas pressure of 50-150 Pa, with a gas mixing ratio of 1:2 to 1:4 and an activation time of 5-30 minutes. A graphite or metal carrier plate is provided in the plasma reaction chamber to enhance plasma uniformity. After activation, the gas is cooled to 40-60℃ by a cooling device before being introduced into the cathode area. The PECVD equipment is equipped with an in-situ spectral monitoring module to detect the type and concentration of active particles in real time and dynamically adjust the radio frequency power and gas mixing ratio according to the detection results.
7. The cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization according to claim 4, characterized in that, The porous gas distributor is made of hydrophobic porous ceramic or polymer material with a pore size range of 10-100 micrometers. The gas distributor is located below or on the side of the cathode catalyst layer and is arranged perpendicular to the electrolyte flow direction.
8. The cyclic process for the electrocatalytic reduction of nitrate to ammonia via PECVD optimization according to claim 1, characterized in that, It also includes step nine: after the reaction is completed, the electrolyte is subjected to solid-liquid separation to recover the suspended catalyst particles, and the surface is regenerated by PECVD equipment. The regenerated catalyst is then put back into the next reaction cycle.