Metal-Free Dihydrogen Oxidation by a Borenium Cation: A Combined Electrochemical/Frustrated Lewis Pair Approach**

In order to use H(2) as a clean source of electricity, prohibitively rare and expensive precious metal electrocatalysts, such as Pt, are often used to overcome the large oxidative voltage required to convert H(2) into 2 H(+) and 2 e(−). Herein, we report a metal-free approach to catalyze the oxidation of H(2) by combining the ability of frustrated Lewis pairs (FLPs) to heterolytically cleave H(2) with the in situ electrochemical oxidation of the resulting borohydride. The use of the NHC-stabilized borenium cation [(IiPr(2))(BC(8)H(14))](+) (IiPr(2)=C(3)H(2)(NiPr)(2), NHC=N-heterocyclic carbene) as the Lewis acidic component of the FLP is shown to decrease the voltage required for H(2) oxidation by 910 mV at inexpensive carbon electrodes, a significant energy saving equivalent to 175.6 kJ mol(−1). The NHC–borenium Lewis acid also offers improved catalyst recyclability and chemical stability compared to B(C(6)F(5))(3), the paradigm Lewis acid originally used to pioneer our combined electrochemical/frustrated Lewis pair approach.