A dual-electrolyte system for photoelectrochemical hydrogen generation using CuInS2-In2O3-TiO2 nanotube array thin film

The utilization of Na2S/Na2SO3 mixture as the electrolyte solution to stabilize sulfide anode in a photoelectrochemical cell for hydrogen evolution generally compromises the current-to-hydrogen efficiency (eta(current)) of the system. Here, the employment of a dual-electrolyte system, that is, Na2S/Na2SO3 mixture and pH-neutral Na2SO4 as the respective electrolyte solutions in the anode and cathode chambers of a water splitting cell is demonstrated to suppress the photocorrosion of CuInS2-In2O3-TiO2 nanotube (CIS-In2O3-TNT) heterostructure, while simultaneously boosts the eta(current). Although n-type CIS and In2O3 nanoparticles can be easily formed on TNT array via facile pulse-assisted electrodeposition method, conformal deposition of the nanoparticles homogeneously on the nanotubes wall with preservation of the TNT hollow structure is shown to be essential for achieving efficient charge generation and separation within the heterostructure. In comparison to Na2S/Na2SO3 solution as the sole electrolyte in both the anode and cathode chambers, introduction of dual electrolyte is shown to not only enhance the photostability of the CIS-In2O3-TNT anode, but also lead to near-unity eta(current) as opposed to the merely 20% eta(current) of the single-electrolyte system.