ZIF-67-derived nanoframes as efficient bifunctional catalysts for overall water splitting in alkaline medium.

In order to lower energy consumption it is critical to develop highly efficient and stable non-precious metal bifunctional catalysts. In this study, we found that rational design of novel nanostructures is able to increase the number of active sites, conductivity and accelerate electron transfer, thus promoting enhanced performance of the catalyst. We successfully synthesized carbon nanotubes (CNTs) containing a hollow polyhedral (CNTHPs) structure through annealing, etching and phosphating. The unique hollow shape not only provides a stable structure but also facilitates mass and charge transfer. Thus, CoP/CNTHPs can catalyze the hydrogen and oxygen evolution reactions effectively with overpotentials of 147 and 238 mV at 10 mA cm-2. Simultaneously, CoP/CNTHPs only needs a voltage of 1.54 V to attain a current density of 10 mA cm-2 in the electrocatalytic water splitting process, demonstrating its bifunctional activity. Furthermore, the electrolytic catalytic performance does not weaken significantly after 12 hours of electrolysis, demonstrating excellent stability. Overall, this research offers useful insights into rational design of high-performance non-noble metal catalysts.

Construction of Fe-doped CoP with hybrid nanostructures as a bifunctional catalyst for overall water splitting.

Due to their open skeleton structures, adjustable active sites and homogeneous catalytic centers, PBA-based materials have promising applications in electrochemical water splitting. Herein, we report a PBA derived Fe0.25-CoP electrocatalyst with a hybrid nanostructure, which offered a large specific surface area and active sites for the HER and OER, respectively. The as-synthesized Fe0.25-CoP catalyst exhibits remarkable catalytic performance and durability at overpotentials of 262 mV for the OER and 111 mV for the HER, requiring a voltage of merely 1.57 V to achieve a current density of 10 mA cm-2 for the electrocatalytic water splitting process. The preeminent activity of Fe0.25-CoP was mainly ascribed to the framework structures of Co-PBA and appropriate doping of Fe3+ which regulated the electronic structures and morphology of Fe0.25-CoP. In addition, the partial phosphating strategy retained the active centers for the OER in Co-PBA, which were further enhanced by the catalysis of Fe3+. In short, the rational design and regulation of catalyst structures and compositions is a promising approach for the development of highly efficient water splitting catalysts.