Graphene-coated copper nanowire networks as a highly stable transparent electrode in harsh environments toward efficient electrocatalytic hydrogen evolution reactions

Copper nanowire networks (NWs) coated with a graphene layer through a carbon-enclosed chemical vapor deposition technique at a low temperature of 400 °C with a low sheet resistance of 23.2 Ω sq^-1 and a high transmittance of 83.4%, which is comparable to the typical values of tin-doped indium oxide (ITO), as a transparent conducting electrode were demonstrated. The graphene-coated copper NW networks retain a low sheet resistance of less than 25 Ω sq^-1 even after annealing at a temperature of 240 °C in a pure oxygen environment for 1 h, while a sheet resistance less than 100 Ω sq^-1 can still be maintained in natural sea water, and acidic and basic solutions. Their highly stable features in harsh environments make these graphene-coated copper nanowire networks suitable as a catalyst toward high-efficiency hydrogen evolution reactions (HERs) with a low overpotential of 252 mV at 10 mA Cm^-2 and a low Tafel slope of 67 mV dec^-1. The non-corrosive and anti-oxidant graphene-coated copper nanowire networks could be used as an alternative transparent conducting electrode in harsh environments, such as in tandem photocatalytic water splitting.