Compacted stainless steel mesh-supported Co3O4 porous nanobelts for HCHO catalytic oxidation and Co3O4@Co3S4 via in situ sulfurization as platinum-free counter electrode for flexible dye-sensitized solar cells

Abstract

Noble metal Pt is usually employed as the effective catalyst for HCHO oxidation and counter electrode (CE) of dye-sensitized solar cell (DSSC), but its low reserve and high cost inspire the exploration of more efficient and low-cost alternatives. In this study, first, Co3O4 porous nanobelts were directly grown on compacted stainless steel mesh (CSSM) by simple hydrothermal method with post heat-treatment. Due to the synergistic effect of Co3O4 and flexible substrate, this immobilized Co3O4 exhibited stronger catalytic activity and stability for HCHO oxidation compared to powdered Co3O4 with similar morphology; Second, the immobilized Co3O4 film was converted to Co3O4@Co3S4 porous nanobelts film via in-situ sulfurization reaction for various periods. The obtained Co3O4@Co3S4 was used as the CE of flexible DSSCs, and a maximum power conversion efficiency of 5.30% was achieved, which was higher than that of the DSSC with a sputtered Pt CE (5.23%). Furthermore, the FDSSCs using this CE still preserved over 93% of its initial conversion efficiency after consecutive bending tests with different angles and 15-day aging test. The excellent electrocatalytic activity, mechanical and long-term stability and low material cost of the optimized Co3O4@Co3S4 electrode provide it with promising potential application as CE of FDSSCs.