Electrocatalytic Hydrogen Evolution Using A₂B-type Corrole Cobalt Complex

The increasing demand of global energy necessitate the development of clean energy.Hydrogen is an ideal fuel with high energy-density and the combustion product is only water.Electrochemical water splitting provides an attracting storage strategy for renewable sources such as solar,wind and hydro power by converting electric energy to chemical H₂fuel.It is important to both energy conversion and storage.However,how to find out the substitute of Pt with low price and high activity is still a challenge.In this work,we design three molecular catalysts and testing their ability as HER catalyst:Three BPCC,BPPC,BPDC free base corrole and their cobalt triaryl corroles?Co?BPCC?PPh₃,Co?BPPC?PPh₃,Co?BPDC?PPh₃?bearing electron-withdrawing or electron-donating group at 10-meso position have been synthesized and characterized.These cobalt corroles were well characterized by HR-MS,UV-Vis,NMR,XPS and single crystal X-ray structure determination.In no-aqueous?DMF?solution?containing TBAP as supporting electrolyte?,with the introduce of withdrawing group in 10-meso-phenyl position,Co ^I/Co ^IIcouple shifted to anodic direction.The peak current increase with the gradual addition of acetic,indicating that it was a catalytic?Hydrogen Evolution Reaction,HER?process.When adding 16eq acetic acid,the peak current of Co?BPCC?PPh₃,Co?BPPC?PPh₃,Co?BPDC?PPh₃is 22?A,12?A,10?A,respectively.Base on the CV result,the proposed catalytic pathway for HER mediated by cobalt corroles could be inferred,[Co ^III-PPh₃]go through 1e^-reduction and dissociation of PPh₃to generate[Co^II]^-species.Then[Co^II]^-becomes[Co^I]^2-via 1e^-reduction,and it bonds a proton to form[Co ^II-H]^-.[Co ^II-H]^-further reacted with H⁺to release H₂.We evaluate these cobalt corroles by comparing their turn-over frequency?TOF?at different overpotentials.CPE experiment shows that,when overpotential at 548 m V,the TOF?turnover frequency?is 46.5 h^-1,18.9 h^-1,19.3 h^-1in DMF solution.We further evaluated their HER ability in aqueous solution.All these cobalt corrole performd better in aqueous solution when using water as proton source.The stable electrolysis current and the UV-Vis of cobalt corrole demonstrate all the complexes are stable during electrolytic process.