Effects of different dithiolate ligands on electrocatalytic hydrogen production of nickel complexes in acetic acid or water

Abstract

In order to solve the problems of fossil energy depletion and environmental pollution, it is necessary to find new energy sources that are recyclable and environmentally friendly. Among them, hydrogen is a high calorific value, clean and sustainable energy. At present, hydrogen is mainly obtained by electrolysis of water. The use of electrocatalysts in this process can effectively reduce the consumption of electrical energy. In this study, three molecular electrocatalysts based on nickel complexes, [BzTPP]2[Ni(mnt)2](1), [BzTPP]2[Ni(i-mnt)2](2), and [BzTPP]2[Ni(tdas)2](3) ([BzTPP]+ = 1-benzyltriphenylphosphinium, mnt = 1,2-dicyanoethylene-1,2-dithiolate, i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and, and tdas = 1,2,5-thiadiazole-3,4-dithiolate), were systemically investigated. Electrochemical study showed three complexes can electrocatalyze hydrogen generation from acetic acid or aqueous buffer solution, and afford a turnover frequency (TOF) of 504.76, 591.52 and 1022.93 mol of hydrogen per mole of catalyst per hour at an overpotential (OP) of 0.838 V from a neutral buffer. It is shown that [NiII(tdas)2]2−exhibits higher electro-catalytic hydrogen production activity than [NiII(mnt)2]2− and [NiII(i-mnt)2]2−. This provides a new chemical paradigm for the design and fabrication of efficient molecular catalysts for water reduction.