Affiliation:
1. Institute of Materials Chemistry Technische Universität Wien (TU Wien) Getreidemarkt 9 Vienna 1060 Austria
2. Materials Design Department of Physics Chemistry and Biology (IFM) Linköping University Linköping 58183 Sweden
Abstract
AbstractThermal treatments can have detrimental effects on the photocatalytic hydrogen (H2) evolution performance and impact the formation mechanism of the active state of surface‐supported co‐catalysts. In this work, a range of Ni‐based co‐catalysts is investigated immobilized on TiO2, evaluated their H2 evolution rates in situ over 21 h, and analyzed the samples at various stages with a comprehensive set of spectroscopic and microscopy techniques. It is found that achieving the optimal hydrogen evolution (HER) performance requires the right Ni0:Ni2+ ratio, rather than only Ni0, and that Ni needs to be weakly adsorbed on the TiO2 surface to create a dynamic state. Under these conditions, Ni can undergo an efficient redox shuttle, involving the transformation of Ni2+ to Ni0 and back after releasing the accumulated electrons for H+ reduction (i.e., Ni2+ ↔ Ni0). Yet, when the calcination temperature of the Ni/TiO2 photocatalysts increases, resulting in stronger coordination/adsorption of Ni on TiO2, this process is gradually inhibited, which ultimately leads to decreased HER performances. This work emphasizes the significance and influence of thermal treatments on the Ni active state formation – a process that can be relevant to other HER co‐catalysts.
Funder
Österreichische Forschungsförderungsgesellschaft
Austrian Science Fund
Subject
Mechanical Engineering,Mechanics of Materials