随着全球能源危机和环境污染日益加剧,开发可持续的绿色能源技术已经成为当务之急.其中,水分解制氢作为一种清洁能源的生产方式,因其零排放和高能量密度的特点,而受到广泛的研究和关注.析氢反应(HER)和析氧反应(OER)是水分解过程的关键步骤,它们的反应效率直接影响整个制氢过程的能量转换效率.因此,开发高效的双功能电催化剂对于推动水分解技术的发展具有重要意义.本文制备了一种超低Ru掺杂的新型核壳纳米结构电催化剂,该催化剂生长在泡沫镍(NF)上,简称Ru-NiMoO4@Ni3(PO4)2/NF.首先,通过水热法在NF上均匀生长了水合NiMoO4纳米柱,并通过共价相互作用,确保其在垂直方向上有序排列.随后,采用超低浓度的RuC13对NiMoO4纳米柱进行蚀刻,并通过磷酸化反应引入(PO4)3+离子形成了Ni3(PO4)2壳层.这种设计克服了以往Ru易团聚的难题,保障了Ru的均匀分布,从而合成Ru-NiMoO4@Ni3(PO4)2/NF催化剂.通过X-射线衍射、X-射线光电子能谱及透射电子显微镜等对催化剂的化学组分和微观结构进行了分析,证实其成功制备.元素分析结果表明,催化剂中Ru的含量仅为1.94 wt％,显著降低了其制备成本.电化学测试结果表明,该催化剂在HER和OER中均表现出较好的催化活性.在10和100 mA cm-2电流密度下,HER的过电位分别为-14.8和-57.1 mV,Tafel斜率为35.8 mV dec-1,优于商业Pt/C催化剂;在100 mA cm-2电流密度下,OER过电位为259.7 mV,Tafel斜率为21.6 mV dec-1,优于商业RuO2催化剂.在全水解测试中,该催化剂在10和100 mA cm-2时所需的电池电压分别为1.43和1.68 V,与其他自支撑材料相比表现出良好的性能.此外,该催化剂在150 h性能测试过程中表现出较好的稳定性.采用密度泛函理论计算研究了催化剂具有较好活性的内在机制.结果表明,其具有低水离解能垒(△Gb=0.46 eV),接近零的HER自由吸附能(△G*H=0.02 eV),低的OER自由吸附能量(△G*OOH-△G*OH=2.74 eV)和接近费米能级的高密度态.这些特性共同促进了电解水反应的高效进行.综上,本文研究开发的Ru-NiMoO4@Ni3(PO4)2/NF双功能催化剂具有较好的催化活性、低电位需求和长期稳定性,为氢气生产开辟了新途径,也为优化双功能水分解催化剂提供了新视角,并为未来可持续能源应用发展提供一定的参考.
Ultralow Ru-doped NiMoO4@Ni3(PO4)2 core-shell nanostructures for improved overall water splitting
The potential of sustainable hydrogen production technology through water splitting necessitates the rational design of oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)bi-functional electrocatalysts.In this context,we initially synthesized and empirically evaluated ultralow Ru-doped NiMoO4@Ni3(PO4)2 core-shell nanostructures on nickel foam(Ru-NiMoO4@Ni3(PO4)2/NF).The hydrous NiMoC4 nanopillars were hydrothermally grown on NF,followed by successive RuCl3 etching and subsequent phosphorylation processes,leading to the final Ru-NiMoO4@Ni3(PO4)2/NF.The catalyst demonstrated impressive HER overpotential values of-14.8 and-57.1 mV at 10 and 100 mA cm-2,respectively,with a Tafel slope of 35.8 mV dec1.For OER at 100 mA cm2,an overpotential of 259.7 mV was observed,with a Tafel slope of 21.6 mV dec1.The cell voltage required for overall water splitting was 1.43 V at 10 mA cm-2 and 1.68 V at 100 mA cm-2.Moreover,the catalyst exhibited superior stability for 150 h,emphasizing its practical utility for long-term applications.Subsequent density functional theory calculations aligned with these empirical findings,indicating a low water dissociation energy barrier(△Gb=0.46 eV),near-zero free adsorption energy for HER(△G*H=0.02 eV),and suitable free adsorption energy for OER(△G*OOH-△G*OH=2.74 eV),alongside a high density of states near the Fermi level.These results,informed by both experimental evaluation and theoretical validation,highlight the potential of Ru-NiMoO4@Ni3(PO4)2/NF as a high-performance catalyst for water splitting,setting a solid founda-tion for advancements in sustainable energy technologies.
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