High-Yield and Selective Photoelectrocatalytic Reduction of CO₂ to Formate by Metallic Copper Decorated Co₃O₄ Nanotube Arrays

Abstract

Carbon dioxide (CO2) reduction to useful chemicals is of great significance to global climate and energy supply. In this study, CO2 has been photoelectrocatalytically reduced to formate at metallic Cu nanoparticles (Cu NPs) decorated Co3O4 nanotube arrays (NTs) with high yield and high selectivity of nearly 100%. Noticeably, up to 6.75 mmol·L(–1)·cm(–2) of formate was produced in an 8 h photoelectrochemical process, representing one of the highest yields among those in the literature. The results of scanning electron microscopy, transmission electron microscopy and photoelectrochemical characterization demonstrated that the enhanced production of formate was attributable to the self-supported Co3O4 NTs/Co structure and the interface band structure of Co3O4 NTs and metallic Cu NPs. Furthermore, a possible two-electron reduction mechanism on the selective PEC CO2 reduction to formate at the Cu–Co3O4 NTs was explored. The first electron reduction intermediate, CO2 ads•–, was adsorbed on Cu in the form of Cu–O. With the carbon atom suspended in solution, CO2 ads•– is readily protonated to form the HCOO– radical. And HCOO– as a product rapidly desorbs from the copper surface with a second electron transfer to the adsorbed species.

Role of the oxide layer on Sn electrode in electrochemical reduction of CO 2 to formate

“…The transformation of CO 2 into value-added chemicals and fuels has attracted much attention in recent years. Up to now, many chemical, photochemical, electrochemical and photoelectrochemical methods have been investigated for the purpose [2][3][4]. Among these routes, electrochemical reduction of CO 2 represents a potentially "clean" technique only at the expense of a sustainable supply of electric energy [5].…”

Recent progress on advanced design for photoelectrochemical reduction of CO2 to fuels

“…However, semiconductor photocathodes often show the frustrating activity in CO 2 reduction due to the deficiency of active sites for CO 2 activation. It is a promising strategy for effectively surmounting this predicament that highly efficient catalysts such as metal nanoparticles [75,76] and homogeneous metal complexes [21,34,46] as co-catalysts are anchored on the surface of photocathodes. The involvement of co-catalysts can facilitate CO 2 activation, modulate reaction pathways and maneuver desirable products, which have been extensively applied to PEC CO 2 reduction.…”

“…4a-c) [29]. In comparison with planar p-Si photocathodes, 1D Anchoring cocatalysts on photocathodes Sn-coupled p-Si nanowire arrays [76], were also designed as 1D nanostructures for photocathodes toward PEC CO 2 reduction. The 1D geometry favored light harvesting and provided more active sites for CO 2 conversion, exhibiting high selectivity and FE for CH 3 OH and formate, respectively.…”

Highly Efficient and Visible Light Responsive Heterojunction Composites as Dual Photoelectrodes for Photocatalytic Fuel Cell

“…CuO was prepared by a pulsed galvanostat method under high current conditions [36]. The electrodeposition was carried out in a conventional three-electrode electrochemical workstation (CS310, CorrTest, Wuhan, China) with a conditioned electrolyte solution of 0.4 mol L −1 CuSO 4 and 3 mol L −1 lactic acid fixing the pH at 7 by NaOH and the temperature at 25 • C. The concentrated lactic acid acts as a complex agent for the stabilization of copper ions [37].…”