A kind of method of utilizing the formic acid electrolysis to produce hydrogen
Technical field
The present invention relates to a kind of hydrogen method of producing based on the solid polymer dielectric film electrolyzer.With the aqueous formic acid is anode electrolysis fuel, applies certain voltage in the cathode and anode both sides, makes formic acid generation electrocatalysis oxidation reaction; The proton that anode-side produces conducts to cathode side through film, and combines to generate hydrogen again in electronics.
Background technology
It is abundant that Hydrogen Energy has the source, and the characteristics of clean and effective are might be at the secondary energy sources of the very important effect of performance on the 21 century world energy sources stage.And be that Proton Exchange Membrane Fuel Cells (PEMFC) technology of fuel has obtained significant progress in recent years with hydrogen.Fuel cell might solve " energy " and " environmental protection " this two big worlds difficult problem, and will be significant for human social.Yet, how to realize economy, to produce hydrogen efficiently most important to the Hydrogen Energy expanding economy.
At present, the method for small-scale hydrogen manufacturing commonly used mainly contains methyl alcohol/gas renormalizing hydrogen manufacturing and water electrolysis hydrogen producing dual mode.Wherein, the course of reaction of reformation hydrogen production is complicated, and system is huge, and is poor to equipment requirements height and mobility; And electrolytic hydrogen production has that device is simple, equipment moulding, the characteristics that are easy to use, is highly suitable for on-the-spot hydrogen manufacturing and application on a small scale.
The electrolysis unit that is used for electrolytic hydrogen production mainly contains two types.A kind of is the alkaline electrolysis device, promptly in electrolytic cell, adds a certain amount of alkali or salt to strengthen conductivity, obtains hydrogen and oxygen respectively in anode and cathode, utilizes this electrolysis unit brine electrolysis to produce hydrogen and still has high, the less economical problem of energy consumption; The another kind of electrolyzer (Solid-PEM electrolyzer) that just is based on the solid electrolyte film type.This device has simple to operate, and anode and cathode separately and can keep certain partial pressure avoids the use of advantage such as alkali lye and in industry, is used widely.
Because water electrolysis hydrogen production, its theoretical decomposition voltage is 1.23V, and in the actual electrolytic hydrogen production process, owing to there is certain loss, its decomposition voltage is up to more than the 1.4-1.5V; And high energy consumption is to realize the very big obstacle of extensive water electrolysis hydrogen producing.Formic acid is as liquid fuel and hydrogen source, have to be easy to carry, hydrogen content high (4.3%), advantages of environment protection, and the most important thing is its theoretical decomposition voltage low (have only-0.02V).These characteristics make formic acid electrolytic hydrogen production required voltage be significantly less than the water electrolysis hydrogen producing required voltage, save the consumption of electric energy greatly, also for the on-the-spot hydrogen manufacturing of small-scale new approaches are provided.
Summary of the invention
The object of the present invention is to provide a kind of energy-conservation, efficiently, the on-the-spot method of producing hydrogen easily.
For realizing above-mentioned purpose, the technical scheme that the present invention adopts is:
With the aqueous formic acid is fuel, adopts the electrolyzer of solid polymer dielectric film to produce hydrogen;
Specifically may further comprise the steps: between electrolysis electrode anode and negative electrode, apply decomposition voltage, and, make formic acid at anode generation electrocatalysis oxidation reaction in the aqueous formic acid of the anode-side feeding>=2M of electrolysis electrode, the electric current that produces electrolysis, current density is 50-350mA/cm
2, produce hydrogen at cathode side; The electrolyzer temperature is controlled between 20-70 ℃.
The solid polymer dielectric film electrolyzer comprises plate, cathode plate and places the electrolysis electrode between pole plate; Electrolysis electrode is clamped in formation polymer dielectric film electrolyzer between two pole plates, and pole plate is provided with the flow field near electrolysis electrode one side.
The preparation of electrolysis electrode: after electrolysis electrode was superimposed together by cathode diffusion layer, cathode catalysis layer, dielectric film, anode catalyst layer, anode diffusion layer successively, hot pressing 1-5min under 1000-2000 pound pressure formed electrolysis electrode.
On cathode diffusion layer, scribble Pt/C or Pd/C catalyst, form cathode catalysis layer, and constitute the negative electrode of electrolysis electrode with cathode diffusion layer; Cathode catalysis layer noble metal carrying capacity is 1-2mg/cm
2
On anode diffusion layer, scribble Pd/C, PdAu/C, PdSn/C, a kind of catalyst among the PdIr/C or two or more catalyst combination form anode catalyst layer, and constitute the anode of electrolysis electrode with anode diffusion layer.Anode catalyst layer noble metal carrying capacity is 2-5mg/cm
2
Electrolyte membrane
Series film or
in a modified membrane.
The cathode and anode diffusion layer of electrode is carbon paper, carbon cloth or the carbon felt that adopts the PTFE hydrophobic to handle, and wherein PTFE quality percentage composition is 10-30%.
During electrolysis, negative electrode can feed the N of 20-40sccm
2, hydrogen is taken out of, or is not fed gas (the hydrogen self-diffusion goes out negative electrode).The charging flow velocity of electrolyte formic acid is 1-5ml/min.
The concentration optimum of electrolyte formic acid is 6-10M.The decomposition voltage that applies between the anode of electrolysis electrode and negative electrode is generally 0.3-1V.
Its hydrogen that is produced by negative electrode adopts drainage to collect or the use that directly acts as a fuel;
Directly act as a fuel when using; With formic acid is fuel; Hydrogen that the polymer dielectric film electrolyzer is produced and Proton Exchange Membrane Fuel Cells coupling; The hydrogen that makes collects and directly feeds the anode of Proton Exchange Membrane Fuel Cells (PEMFC) through self-diffusion, as anode reaction fuel, produce electric energy.
The formic acid that utilizes according to the invention is electrolysis fuel, comes electrolysis to produce the method for hydrogen with the polymer dielectric film electrolyzer.Comparing with traditional reformation hydrogen production is a kind of simple, convenient, hydrogen production process fast and flexibly; Compare with other electrolysis fuel electrolytic hydrogen productions such as utilizing water or methyl alcohol, have the advantage that decomposition voltage is low, energy consumption is little, hydrogen production efficiency is high.This method of producing hydrogen can combine with primary energy such as solar energy, wind energies; Utilize primary energy cheap and easy to get that electric power is provided; With formic acid is fuel, and hydrogen is produced in on-the-spot electrolysis, and small-sized removable power-supply device such as fueling battery car uses or stores.The present invention also for the on-the-spot hydrogen manufacturing of small-scale provides new approaches and approach, helps further promoting the Hydrogen Energy expanding economy to realize with final when reducing the electrolytic hydrogen production energy consumption.
Description of drawings
Fig. 1 formic acid electrolysis hydrogen production device sketch map.
Wherein, a is the anode-side of electrolyzer; B is the cathode side of electrolyzer; C is a dielectric film; D is a DC power supply.
Fig. 2 is 60 ℃, under the 1V decomposition voltage, and during different aqueous formic acid concentration charging, the variation relation of Faradaic current and hydrogen-producing speed.
Fig. 3 is 60 ℃, during the charging of 6M aqueous formic acid, and the variation tendency of the Faradaic current under the different decomposition voltages.
Fig. 4 is for to produce hydrogen and Proton Exchange Membrane Fuel Cells (PEMFC) coupling sketch map with formic acid for the fuel electrolysis.
Wherein, 1 is No. 5 batteries of a joint, rated voltage 1.5V; 2 is the anode of electrolyzer; 3 is the negative electrode of electrolyzer; 4 is dielectric film; 5 is the anode of Proton Exchange Membrane Fuel Cells; 6 is the negative electrode of Proton Exchange Membrane Fuel Cells; 7 is small fan; 8 is hydrogen pipeline; Circuit connection is represented with single solid line.
Embodiment
Embodiment 1
Assemble the polymer dielectric film electrolyzer by Fig. 1, the carbon paper (Toray-060) that its cathode and anode diffusion layer adopts the PTFE hydrophobic to handle, wherein anode PTFE quality percentage composition is 15%, negative electrode PTFE quality percentage composition is 30%.Anode catalyst is Pd/C, is sprayed on the anode diffusion layer, and loading is 2mg/cm
2Cathod catalyst is Pt/C, is sprayed on the cathode diffusion layer, and carrying capacity is 1mg/cm
2Dielectric film does
-115 films, electrode effective area are 4cm
2The formic acid solution of 2-10M is fed the anode of electrolyzer with the flow velocity of 1ml/min, and negative electrode feeds nitrogen, and its flow velocity is 20sccm.Use PAR273A electrochemical workstation (potentiostat/galvanostat; The Princeton application study) as DC power supply; Apply 0.3-1V voltage at the electrolytic cell two ends; The electrolytic cell temperature is controlled at makes formic acid generation electrocatalysis oxidation reaction under 60 ℃, negative electrode adopts drainage to collect hydrogen, and calculates hydrogen-producing speed.
Fig. 2 is 60 ℃, under the 1V decomposition voltage, and during different aqueous formic acid concentration charging, the variation relation of Faradaic current and hydrogen-producing speed.Can find out that Faradaic current and hydrogen-producing speed are the trend that raises and reduce earlier with formic acid concn; Wherein when aqueous formic acid concentration was 8M, current density reached 314mA/cm
2, hydrogen-producing speed is 9.5ml/min.
Fig. 3 is 60 ℃, during the charging of 6M formic acid, and the variation tendency of the Faradaic current under the different decomposition voltages.Raise with decomposition voltage, electrolysis performance (electric current) also increases.When 0.6V, current density reaches 110mA/cm
2
Embodiment 2:
Fig. 4 produces hydrogen and Proton Exchange Membrane Fuel Cells (PEMFC) coupling instance for being fuel with the aqueous formic acid with the electrolysis of polymer dielectric film electrolyzer.
Electrolysis power is joint No. 5 batteries (rated voltage 1.5V) among the figure; Electrolyzer is that two electrolysis electrodes are in series, and constitutes with bipolar plates.Owing to there is ohmic loss, the voltage of surveying two series connection electrolysis electrodes is all in the 0.65-0.68V scope.
The anode catalyst of electrolysis electrode is Pd/C, and loading is 3mg/cm
2, cathod catalyst is Pt/C, loading is 1mg/cm
2, electrode area is 16cm altogether
2
Proton Exchange Membrane Fuel Cells among the figure (PEMFC) cathode and anode catalyst is Pt/C, and loading is 0.4mg/cm
2, and negative electrode adopts air from breathing pattern, and electrode area is 8cm
2
The anode formic acid feed cavity volume of electrolyzer is 20ml among the figure, and aqueous formic acid concentration is 8M, and the hydrogen that negative electrode produces is through the anode-side of pipeline self-diffusion to Proton Exchange Membrane Fuel Cells, as the anode reaction fuel of Proton Exchange Membrane Fuel Cells.
During test, the whole system circuit is connected, the anode generation formic acid electrocatalysis oxidation reaction of electrolyzer produces hydrogen at cathode side.The hydrogen that produces is accumulative total in the negative electrode cavity of electrolyzer, and diffuse in the anode cavities of Proton Exchange Membrane Fuel Cells, as its anode reaction fuel.Produce electric energy under the common reaction of the oxygen of Proton Exchange Membrane Fuel Cells in anode hydrogen gas, cathode air, driven small fan work.