Jet nebulizer-spray coated CZTS film as Pt-free electrocatalyst in photoelectrocatalytic fuel cells

Abstract

The copper zinc tin sulphide (CZTS) is a promising p-type earth abundant alloy that received profound attention as an electron driven dark catalyst in electrocatalytic reduction reactions. In particular, the photoelectrocatalysis based solar fuel cell encompass with inexpensive electrocatalyst (hydrogen evolution reaction) is anticipated to support to reduce the overall system cost. However, demonstrating CZTS as Pt-free counter electrode in photoelectrocatalytic fuel cells is scarce. Because, achieving high electronic conductivity, favourable (1 1 2) crystalline structure towards high electrocatalytic property through low cost vacuum-free technique is remains challenge. In this report, we demonstrate p-type CZTS film fabrication at different processing temperature (250, 300, and 350 °C) using jet nebulizer spray (JNS) coating technique. The processing temperature play a key role on crystalline property, composition, and catalytic activity of CZTS. The x-ray diffraction and energy dispersive analysis results reveals that the CZTS film prepared 250 °C exhibit kesterite structure oriented in (1 1 2) direction. The electrocatalytic reduction property of as-synthesised CZTS electrodes in water reduction process is tested in aqueous 1 M NaOH solution. Among the different temperature processed films, CZTS prepared at 250 °C result high electrocatalytic reduction activity ∼-2.1 mA cm−2 at -0.44 V vs Ag/AgCl. In addition, these film exhibits high electrical conductivity than that of other CZTS samples. Therefore, optimised CZTS 250 °C film is further examined in hydrogen peroxide (H2O2) reduction which result enhanced electrical current generation after adding the 1 M of hydrogen peroxide in PBS electrolyte based electrochemical cell. This encouraged to apply as Pt-free counter electrode in H2O2 electrolyte based photoelectrocatalytic fuel cells. The PEC cells encompass with TiO2 nanowire photoelectrode, and CZTS-250 °C counter electrode showed feasible photocurrent generation compared to conventional Pt counter electrode. This proof-of-concept type Pt-free PEC cells leads to open new paths in implementing wide-range of semiconductor based electrocatalyst to support in development of low-cost photoelectrocatalytic fuel cells.