Enhanced single-nanoparticle collisions for the hydrogen evolution reaction in a confined microchannel

限域微通道增强的单颗粒碰撞电催化析氢

Single nanoparticle(NP)collisions technique has been widely employed in electrocatalysis.However,the short collision duration of single NPs hinders the further improvement in their electrocatalytic performance.Here,to increase the dynamic collision duration of single NPs in the electron tunneling region,enhanced near-wall hindered diffusion is introduced in the stochastic collision process by coupling a Au ultramicroelectrode(UME)with a confined microchannel.In the case of single palladium nanoparticle(Pd NP)collisions for the hydrogen evolution reaction(HER),the hydrodynamic trapping confined in the microchannel effectively permits the activation of the HER on the single Pd NPs.The microchannel-based Au UME is promising in the application of single-NP collisions to energy conversion.

单颗粒碰撞电化学已被用于纳米电催化过程的研究,但纳米催化剂与底物的碰撞时间较短限制了其催化性能的提升.在电催化过程中,需要延长单个纳米颗粒在电极界面电子隧穿区中的停留时间,从而提升单个纳米颗粒的催化效率.本文设计和制备了基于限域微通道的超微电极芯片,使单个纳米颗粒获得足够的界面“感受”电势,提高催化效率.以钯纳米颗粒电催化析氢为模型体系,探究了微通道对钯纳米颗粒随机碰撞电化学动态过程的影响.结果表明,当单个钯纳米颗粒运动至10μm尺度以下的微通道近壁区时,流体动力学限域作用使颗粒的布朗运动受阻,使得其在电子隧穿区的随机扩散速度降低.运动受限的钯纳米颗粒停留在超微电极界面的时间延长,有效地催化电极界面发生析氢反应.作为对比,钯纳米颗粒与传统金超微电极界面进行随机碰撞则难以催化析氢反应.此外,在电催化析氢的电压范围内,单个钯纳米颗粒在电极界面电子隧穿区内的停留时间随过电位增大而减小,这是由于在微通道两端施加电压会造成电渗现象,引起限域微通道中流体运动,从而带动溶液中钯纳米颗粒的运动,且电压升高使得电渗流增大,促使纳米颗粒快速远离电极界面.微通道限域增强的机制有助于调控流体动力学控制的催化剂动态扩散传质,从而增加单个纳米颗粒在电极界面的有效碰撞几率,有望促进单颗粒碰撞电化学在电催化领域的实际应用.