A review on photocatalytic methane conversion systems: from fundamental mechanisms to the emerging role of ferroelectric materials

Abstract

Methane (CH4) conversion is a promising strategy for reducing greenhouse gases, synthesizing high-value-added chemicals, and thus achieving carbon neutralization. However, due to its inertness, CH4 requires high energy input to initiate the conversion process, which always leads to excessive energy consumption and catalyst deactivation. Along these lines, the use of sunlight as energy input has demonstrated enormous potential to help overcome the uphill thermodynamics of methane conversion under mild reaction conditions. Nevertheless, the high recombination rate of photoinduced charge carriers still hampers photocatalytic efficiency. In the past years, ferroelectric photocatalysts have attracted much attention for dealing with sluggish charge separation/transfer dynamics, presenting themselves as excellent materials for enhancing photocatalytic CH4 conversion rates under mild conditions. Consequently, this work reviews and discusses four pivotal photocatalytic CH4 conversion routes, including (i) dry reforming of methane (DRM), (ii) partial oxidation of methane (POM), (iii) non-oxidative coupling of methane (NOCM), and (iv) oxidative coupling of methane (OCM). In particular, special attention has been paid to the recent advances in ferroelectric-assisted photocatalytic CH4 conversion to elucidate the influence of polarized ferroelectrics in the charge transfer mechanisms. Finally, the main challenges in the field are highlighted, also presenting possible strategies to overcome them in order to encourage more in-depth research on ferroelectric-assisted methane conversion in the future.