膜法酸碱两性电解水制氢基础研究

To meet the needs of sustainable energy development for national great strategy, this project focus on innovation of principle and technology for water electrolysis hydrogen production with lower energy consumption. We innovated an approach to generate hydrogen that membrane based-on acidic/alkaline amphoteric water electrolysis was proposed, in which membrane was fixed between acid and alkali half-cell for water electrolysis, the hydrogen evolution and oxygen electrode were separatively set in acidic and in alkaline aqueous solution. To avoid acid and alkali neutralization reaction, bipolar membrane was used to isolate acidic and alkaline aqueous solution. This proposal investigates the molecular interaction between water and membrane materials, influence of the applied electric field upon water splitting rate into hydrogen and hydroxyl ions, interpreting mechanism of ion migration through membranes, and designing bipolar membrane for acidic/alkaline amphoteric water electrolysis. Based on the principle that acidic environment is benefit for hydrogen evolution, and alkaline condition is good for oxygen generation in water electrolysis process, this novel approach reduces the thermodynamic potential for water electrolysis from 1.23V to 0.40V. Compared with water electrolysis in alkaline solution at cell voltage of 1.8V, hydrogen evolution rate increases by 4-6 times, greatly reducing energy consumption for water electrolysis hydrogen production. The achievement of this proposal will effectively promote the innovation of hydrogen production technology, generating fundamental knowledge for membrane based-on acidic/alkaline amphoteric water electrolysis.

面向能源可持续发展的国家重大战略需求，探索降低电解水制氢能耗的新原理与新方法。提出膜法酸碱两性电解水制氢过程，将双极膜置于析氢电极和析氧电极之间，氢气在酸性水溶液中产生，氧气在碱性环境析出。采用双极膜将酸性、碱性两个腔室隔离，避免发生酸碱中和反应。研究外加电场对膜内水分子解离的作用机理，进行高性能双极膜结构设计与制备，满足酸碱两性电解水制氢需求；解明酸碱溶液组成对电解过程的影响，探索析氢、析氧催化剂和电极制备，发展双极膜电解水制氢过程设计方法。由于酸性水溶液中析氢电势高，碱性水溶液内析氧电势低，电解水制氢的理论电位差从1.23伏降至0.40伏；双极膜将水分子解离为氢离子和氢氧根离子，电解过程不需要外加酸碱。与碱性水溶液电解水制氢相比，析氢速率提高4-6倍（对应1.8V槽电压），大幅度降低制氢能耗。研究成果有效推动新能源制氢技术发展，奠定膜法酸碱两性电解水制氢的理论基础。

为了降低电解水制氢过程能耗，研究酸碱两性电解水制氢原理与工艺。利用离子交换膜作为阳极、阴极之间的隔膜，将酸性、碱性两个腔室隔离，抑制酸碱中和反应。在施加同样电压条件下，酸碱两性电解水制氢速率，显著高于碱性电解的析氢速率，有利于降低制氢能耗。研制成功含有10个单室串联的电解槽，有效面积600cm2，氢气产量达到1.1Nm3/h, 能耗4.1kWh/Nm3H2。从理论与实验两方面，证实了膜法酸碱两性电解水制氢技术优势，为进一步发展低能耗电解槽提供技术路径。.发展自支撑结构析氢、析氧催化电极制备技术，并提出绿色工艺“一步法”制备析氧催化电极。利用泡沫镍铁作为集流体和纳米催化活性位点的原料，通过酸性溶液柔性刻蚀，在空气中氧气和水的共同作用下，泡沫金属表面生长层状双金属氢氧化物纳米片，形成催化活性位点。该泡沫金属电极表面纳米片与基体连接良好，避免脱落后性能衰减，具有高比表面积、高催化活性、高稳定性。通过1200小时连续测试，验证电极稳定性，中试放大后面积达到3000cm2。将其用于电解槽中，在1.84V电压下，电流密度5000A.m-2，是市售镍网电极的1.85倍，制氢能耗4.4kWh.Nm-3H2，达到现行国标规定的一级能效标准。.提出耐碱腐蚀的有机/无机复合离子传导膜绿色制备工艺。利用碱性环境中生长双金属层状氢氧化物（LDH），并原位填充于聚四氟乙烯（PTFE）微孔膜内，制备成功PTFE/LDH复合离子传导膜。在1M的KOH水溶液60℃时，膜面电阻0.4Ω.cm2，经过2000小时无衰减；该膜的泡点压强1.55bar；用于电解水制氢过程，在电流密度500mA cm-2时，连续运行180小时，能耗4.1kWh/Nm3H2。该制膜工艺技术已经进入中试生产线建设阶段，为电解水制氢的电解槽制造提供耐碱离子传导膜产品。