类桑拿法制备的周期性结构Mo金属催化电极及其在电解水制氢中的应用

Sauna-like process prepared periodic molybdenum metal catalytic electrodes and their applications in water reduction

采用类桑拿法制备了聚苯乙烯微球模板,结合双层Mo金属结构,获得了具有周期性结构的Mo金属催化电极.通过控制氧气对聚苯乙烯球的刻蚀时间,可有效调制Mo金属催化电极的横、纵向尺寸,从而获得不同的衬底比表面积.通过原子力显微镜表面形貌测试、电化学线性扫描、塔菲尔测试以及阻抗谱分析表明:增大刻蚀时间可有效提高Mo金属催化电极的表面粗糙度和比表面积,进而降低电荷传输电阻和塔菲尔斜率,促进催化电极/电解液界面处析氢反应的进行.采用类桑拿法和双层Mo金属结构制备周期性结构的方法简单,可大面积化,同时低温磁控溅射法制备的Mo金属催化电极成本低廉,温度兼容多种太阳电池器件,具有形成高效一体化光水解制氢器件的潜力.

To verify that the molybdenum metals exhibit similar catalysis characteristics as the related molybdenum com- pounds, i.e. molybdenum selenide （MoSe2） and molybdenum sulfide （MoS2） which have been well known as the high- performing catalysts for hydrogen evolution reactions, we may thus seek a low-cost, process-simplified, scalable, and highly-catalytic counterpart. We prepared periodic molybdenum （Mo） metal catalytic electrodes by employing self- assembled polystyrene （PS） spheres prepared with a sauna-like method as templates, followed by a reactive ion etching （RIE） process with oxygen gas and a double-layer deposition by low-temperature magnetron sputtering. By controlling the etching time of oxygen gas on PS spheres during the RIE process, the lateral and vertical feature sizes of Mo catalytic electrodes can be efficiently controlled, thereby having various surface area ratios. According to surface morphologies from atomic force microscopy, electrochemical linear sweep voltammetry, Tafel, and impendency measurements, we have found that the surface roughness and surface area ratios of Mo metal catalytic electrodes can be enhanced by prolonging the etching times of PS sphereS, thereby reducing the charge transfer resistances and TaM slopes, and then improving the hydrogen evolution reactions at the catalysts/electrolyte interfaces. We attribute this improvement to the fact that the Mo metal catalytic electrodes can efficiently form beneficial Schottky junctions with the electrolyte to enhance the carrier transportation, and the increased surface area ratios can improve the effective area of the Schottky junctions, thereby enhancing the carrier transportation at the catalysts/electrolyte interfaces. Tafel slope of the periodic Mo metal cat- alytic electrodes in our work is as low as about 53.9 mV/dec, equivalent to highly catalytic materials MoS2 （55 mV/dec） and MoSe2 （105-120 mV/dec）. The proposed periodic Mo catalytic electrodes, which combine a simple sauna-like self- assembly process with a double-layer Mo architecture is scalable and simple; and the surface area of periodic Mo metal catalytic electrodes can also be flexibly controlled, so that the low-temperature magnetron sputtered Mo metal catalytic electrodes are cost-effective and highly compatible with various photovoltaic devices, highlighting the great potential to form high efficient monolithic solar-water-splitting devices.