电解水技术是一种生产高纯氢燃料的方法,能够增强可再生能源发电系统的消纳能力.相较于质子交换膜(PEM)电解槽,碱性(ALK)电解槽可以使用非贵金属基催化电极,拥有更高的经济效益和市场占有率.然而,由于ALK电解槽处于质子稀缺环境,阴极氢气演化反应(HER)动力学变得更加复杂,需要快速解离水分子提供动态质子微环境.硫化钼(MoS2)纳米片边缘具有合适的质子吸附和演化的活性位点,是制备HER催化剂的潜力材料.但其二维基面原子由于配位饱和,显示出较弱的质子吸附能力.如何调控MoS2基面以实现水解动力与质子吸附演化动力的集成,提升MoS2纳米片的碱性HER活性,具有重要的科学和应用意义.本文提出了一种Co/O双原子植入策略,精准调控双活性位点及其电子结构,实现了水解离动力和质子吸附演化动力的高效耦联.首先,利用刻蚀和电沉积的两步实验法,在MoS2基面上成功引入O和Co原子;随后,结合高分辨透射电镜、高角环形暗场-扫描透射电子显微镜、同步辐射X射线吸收精细结构谱等表征分析技术,精准识别了掺杂Co/O原子的位置和配位情况:O原子替换部分S原子,Co原子占据Mo原子的上方,构建出立体凸起的"O-Co-S2"配位构型.催化在线的原位表征分析结果表明:该独特的"O-Co-S2"原子基序发挥着水解离与氢演化反应协同催化效应.密度泛函理论计算结果也证实了该协同机制,其中Co位点促进水的解离反应,而S位点则有助于质子的转化生成氢气.因此,Co/O掺杂MoS2催化剂(Co-O@MoS2)表现出较好的碱性HER活性:仅需81 mV的过电位,即可达到100 mA cm-2的电流密度,Tafel斜率低至42 mV dec-1,在600 mA cm-2的高电流密度测试中运行300 h活性无衰减.上述碱性HER性能不仅远高于原始的MoS2纳米片,而且也领先于部分已报道结果.综上所述,本文在MoS2基面上构筑了原子级协同催化活性中心,显著促进了碱性HER反应性能,为原子活化工程开发先进催化剂提供参考,在原子级基序构造、表征和功能分析方面提供借鉴.
Atomically tailoring synergistic active centers on molybdenum sulfide basal planes for alkaline hydrogen generation
Alkaline water electrolysis allows the adoption of non-precious metal catalysts,but increases the challenge of cathodic hydrogen evolution reaction(HER)with the proton-deficient environment.Here we report an"all-in-one"design by atomic-level tailoring on molybdenum sulfide(MoS2)basal planes with synergistic active centers to trigger water dissociation for proton supply and mean-while improve proton adsorption for hydrogen evolution.The resultant Co/O-codoped MoS2(Co-O@MoS2)catalyst shows superb alkaline HER activity with a small Tafel slope of 42 mV dec-1 and an overpotential as low as 81 mV at 100 mA cm-2,and considerable stability over 300 h even at industrial-grade high current density of 600 mA cm-2,which are among the best records for pre-cious-metal-free HER catalysts in alkaline media.The markedly enhanced alkaline HER perfor-mance is attributed to the synergistic effect from atomically constructed O-Co-S2 motifs with local electronic interactions,in which Co sites promote the premier water dissociation,and S sites facili-tate proton transition to generate hydrogen,respectively.This work presents an atomic-scale structural modification to create synergistic active sites for alkaline HER and provides insights into the atomic activation engineering towards advanced catalysts.
Alkaline water electrolysisHydrogen evolution reactionMolybdenum sulfideAtomic-scale activationSynergistic active center
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