Hydrogen production from water electrolysis enhanced by coal-based formcoke sacrificial anode
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摘要: 传统炭辅助电解水制氢技术将煤、生物质等碳源直接加入阳极室形成浆液,受炭颗粒、氧化基团和电极之间传递影响,反应速率慢,只有在低电流密度下才能实现电解制氢能耗的降低。以煤为碳源、碱活化生物质为黏结剂、石墨为导电颗粒,通过共成型和共热解工艺获得煤基型焦牺牲阳极,并用于炭辅助水电解制氢过程,可在高电流密度下(50 mA/cm2)显著提高炭辅助水电解制氢效率。电化学测试和阳极材料表征表明,煤基型焦牺牲阳极通过自身的牺牲(被氧化)强化阴极反应,进而实现水电解制氢电化学性能的提高。型焦牺牲阳极在1.23 V( vs. RHE)时,制氢电流密度是铂阳极的87倍,Tafel斜率降低了41%。煤基型焦阳极在50 mA/cm2电流密度下阴极产氢速率是铂阳极体系的2.47倍,但电极电位仅为铂阳极的85%。SEM、TGA、BET、FT-IR和XPS结果表明,电解后牺牲阳极自身被氧化,羧基类C=O键被氧化生成CO2,醚类C–O含量显著增加。研究成果为炭辅助电解水制氢技术提供了全新思路与参考。Abstract: Carbon assisted water electrolysis for hydrogen production usually added carbon sources (such as coal and biomass) into anode cell directly to form carbon slurry. This route always suffered from low current density due to the high mass transfer resistance between carbon particles and anode. The coal-based formcoke sacrificial anode was preparaed by co-forming and co-pyrolysis of coal, alkali-activated biomass and conductive graphite, and formcoke sacrificial anode was used in carbon assisted hydrogen production by water electrolysis. The efficiency of carbon assisted hydrogen production could be significantly improved at high current density (50 mA/cm2). The water electrolysis performance of formcoke sacrificial anode and its microstructure evolution were studied. Results showed the current density of formcoke sacrificial anode were 87 times higher than that of Pt anode at 1.23 V( vs. RHE), and the Tafel slopes also reduced by 41% compaired to that of Pt anode. The H2 formation rate of formcoke sacrificial anode was 2.75 times than that of Pt anode at 50 mA/cm2, while the potential of formcoke sacrificial anode was about 85% of Pt anode. The SEM, TGA, BET, FT-IR and XPS results showed that the sacrificial anode itself were oxidized during water electrolysis. Specifically the carboxyl C=O bond was oxidized to CO2, and the content of C–O bond increased significantly. This research provide a new insight and reference for carbon assisted water electrolysis for hydrogen production.
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表 1 样品的工业分析和元素分析
Table 1 Proximate and ultimate analyses of samples
Sample Proximate analysis wad /% Ultimate analysis wdaf /% M A V FC C H N O* S HS 5.3 9.4 13.2 72.1 72.28 3.41 0.84 21.82 1.65 HS+ 3.9 3.3 30.9 61.9 73.58 3.46 0.94 20.29 1.73 JG 2.04 5.76 75.80 16.40 44.76 5.83 0.81 48.44 0.16 *:by difference 表 2 阳极和阴极气体产物生成量
Table 2 Gas production of anode and cathode
Sample Gas production of
anode / mLGas production of
cathode / mLO2 CO2 H2 Pt-Pt 4.950 − 10.20 SM-Pt 14.83 − 28.77 XJYJ-Pt − 7.622 16.58 −: not detected 表 3 型焦阳极样品的孔结构参数
Table 3 Porosity characteristics of formcoke anode sample
Sample Surface area/
(m2·g−1)Pore volume/
(cm3·g−1)Average pore
diameter d/nmBefore reaction 22.10 0.02710 2.255 After reaction 17.67 0.04310 3.420 表 4 反应前后氧形态及相对含量
Table 4 Oxygen morphology and relative content before and after reaction
Sample Relative content /% C=O(531.3) C–O(532.2) Before reaction 31.95 68.05 After reaction 13.07 86.93 -
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