Mechanistic Studies of the Oxygen Evolution Reaction Mediated by a Nickel-Borate Thin Film Electrocatalyst
Mechanistic Studies of the Oxygen Evolution Reaction Mediated by a Nickel-Borate Thin Film Electrocatalyst
复制标题
DOI：
10.1021/ja3126432
复制
发表时间：
2013-03-06
影响因子：
15
通讯作者：
Nocera, Daniel G.
中科院分区：
文献类型：
--
作者：
Bediako, D. Kwabena;Surendranath, Yogesh;Nocera, Daniel G.
太阳能驱动的水分解效率的关键决定因素是O-2释放催化剂（OEC）的动力学曲线。我们现在报告的动力学剖面的水分解的自组装镍硼酸盐（NiBi）OEC。NiBi的阳极氧化膜的机理研究显示出2.3 X RT/2F的低塔菲尔斜率（在25 ° C下为30 mV/decade）。该塔菲尔斜率与对H+活性的反三阶速率依赖性一起确立了NiBi作为用于水裂解的光电化学装置的构造中的理想催化剂。相比之下，nonanodizedNiBi膜显示显着较差的活动相对于他们的阳极氧化同源物，我们归因于一个更缓慢的电子转移从催化剂静止状态。硼酸盐在OEC活性中显示出两种表面上的拮抗作用：通过使质子耦合电子转移（PCET）成为催化剂活性的传播者和作为活性位点的吸附物的抑制剂。通过定义在周转期间发生的PCET预平衡的性质，与在极端pH下的那些相比，在中间pH下催化剂活性的趋势可以完全逆转。这些结果突出了PCET预平衡在催化剂自组装和营业额中的关键作用，并因此建议重新评估不同催化剂的OEC活性进行比较和合理化。
A critical determinant of solar-driven water splitting efficiency is the kinetic profile of the O-2 evolving catalyst (OEC). We now report the kinetic profiles of water splitting by a self-assembled nickel-borate (NiBi) OEC. Mechanistic studies of anodized films of NiBi exhibit the low Tafel slope of 2.3 X RT/2F (30 mV/decade at 25 degrees C). This Tafel slope together with an inverse third order rate dependence on H+ activity establishes NiBi as an ideal catalyst to be used in the construction of photoelectrochemical devices for water splitting. In contrast, nonanodized NiBi films display significantly poorer activity relative to their anodized congeners that we attribute to a more sluggish electron transfer from the catalyst resting state. Borate is shown to play two ostensibly antagonistic roles in OEC activity: as a promulgator of catalyst activity by enabling proton-coupled electron transfer (PCET) and as an inhibitor in its role as an adsorbate of active sites. By defining the nature of the PCET pre-equilibrium that occurs during turnover, trends in catalyst activity may be completely reversed at intermediate pH as compared to those at pH extremes. These results highlight the critical role of PCET pre-equilibria in catalyst self-assembly and turnover, and accordingly suggest a reassessment in how OEC activities of different catalysts are compared and rationalized.