Stand-alone photoconversion of carbon dioxide on copper oxide wire arrays powered by tungsten trioxide/dye-sensitized solar cell dual absorbers

A photoelectrochemical (PEC) cell composed of a WO3/dye-sensitized solar cell (WO3/DSSC) and copper oxide (CuxO, where x=1 and 2) wire arrays as a dual-absorber photoanode and cathode, respectively, is demonstrated as a stand-alone, durable device for CO2 photoconversion. The CuxO wire arrays, which have high surface-to-volume ratios, exhibit promising electrocatalytic activity for CO2 conversion to CO at Faradaic efficiencies of similar to 80% and similar to 60% at E= -0.2 and -0.4 V vs. RHE, respectively, and H-2 production is minimized at a Faradaic efficiency < similar to 20% in the potential range between -0.2 and -1.0 V vs. RHE. The single-absorber cell of a WO3 photoanode and CuxO wire array cathode couple (WO3-CuxO) requires a minimum overpotential of similar to 0.7 V to drive CO2 conversion. For stand-alone CO2 conversion, a DSSC is coupled to the WO3-CuxO system. In the dual-absorber cell (WO3/DSSC-CuxO), the long-wave band (lambda > ca. 450 nm) passed through the semitransparent WO3 film is absorbed by the dye-sensitized TiO2 electrode of the DSSC. The WO3/DSSC-CuxO shows a potential gain of similar to 0.7 V and is able to successfully drive CO2 conversion on CuxO and simultaneously oxidize water on WO3 without an external power supply. In this stand-alone system, the primary CO2 conversion product is CO, with a solar-to-chemical energy efficiency of similar to 2.5%; H-2 and formate are obtained with energy efficiencies of 0.7% and 0.25%, respectively, in 5 h (overall efficiency similar to 3.45%). Neither CO2 conversion product nor H-2 is found using the single-absorber system. (C) 2016 Elsevier Ltd. All rights reserved.