Low Temperature Nano Mechano-electrocatalytic CH₄ Conversion

Abstract

Transforming natural resources to energy sources, such as converting CH 4 to H 2 and carbon, at high efficiency and low cost is crucial for many industries and environmental sustainability. The high temperature requirement of CH 4 conversion regarding many of the current methods remains a critical bottleneck for their practical uptake. Here we report an approach based on gallium (Ga) liquid metal droplets, Ni(OH) 2 cocatalysts, and mechanical energy input that offers lowtemperature and scalable CH 4 conversion into H 2 and carbon. Mainly driven by the triboelectric voltage, originating from the joint contributions of the cocatalysts during agitation, CH 4 is converted at the Ga and Ni(OH) 2 interface through nanotriboelectrochemical reaction pathways. The efficiency of the system is enhanced when the reaction is performed at an increased pressure. The dehydrogenation of other nongaseous hydrocarbons using this approach is also demonstrated. This technology presents a possible low energy route for CH 4 conversion without involving high temperature and harsh operating conditions.

The Native Oxide Skin of Liquid Metal Ga Nanoparticles Prevents Their Rapid Coalescence during Electrocatalysis

“…13,63 More recently, the involvement of a dynamic oxidized Ga layer forming between the LM Ga and a Ni cocatalyst has been proposed to explain the insurgence of triboelectric effects driving the conversion of methane into carbon. 17 These studies, along with our results, provide In (A), this monolayer persists during CO 2 RR. Instead in (B) and (C) the monolayer is dynamic, meaning that it reduces to pure Ga and it re-forms during the course of electrolysis via coupling with the chemical water reduction (B) or CO 2 RR itself (C).…”

“…Instead, if the surface oxidation of Ga to GaO x was coupled directly with the reduction of CO 2 to CO, the negative applied voltage would regenerate the metallic Ga surface and restart the cycle (Figure C). This model has been referred to as the incipient hydrous oxide adatom mediator (IHOAM) model, and it is similar to the mechanism proposed for Ce catalyst dissolved in Galinstan. , More recently, the involvement of a dynamic oxidized Ga layer forming between the LM Ga and a Ni cocatalyst has been proposed to explain the insurgence of triboelectric effects driving the conversion of methane into carbon . These studies, along with our results, provide credibility to the hypothesis that dynamic Ga oxidation may happen during catalytic processes.…”

“…Recently, the field of LMs has undergone a true renaissance, which has partly been driven by the increasing interest in wearable devices. − Most research has centered on Ga and its alloys due to their low toxicity and melting point. − These materials have also emerged as a new class of catalysts wherein the highly dynamic liquid surface offers greater flexibility compared to solid catalysts. ,− Most of the studies so far have focused on thermal catalysis, including dry re-forming of methane and alkane dehydrogenation. − For example, Pd atoms popping up on the surface of liquid Ga in PdGa alloys were shown to be extremely selective for the dehydrogenation of alkane while being resistant to coke poisoning . Applications of LMs are emerging also in electrocatalysis. − In one example, metallic Ce nanoparticles (NPs) were stabilized within Ga droplets to promote the electrochemical conversion of CO 2 to solid carbonaceous species without undergoing deactivation by the buildup of reaction products . In a second example, a selectivity change from hydrogen evolution to selective electrochemical CO 2 reduction was observed to follow the solid–liquid conversion of a Ga–Sn–In catalyst …”

A liquid metal catalyst for the conversion of ethanol into graphitic carbon layers under an ultrasonic cavitation field

“…The ultrasonically-activated EGaIn liquid metals would also encourage further research on thermal catalytic conversions such as CO 2 41 and CH 4 . 42 This work was financially supported by the JSPS KAKENHI under Grant No. JP 20K21095 and 22H01915.…”

CO2 reduction on the Li–Ga liquid metal surface

“…10 In addition, liquid metals have more accessible delocalized metal atoms and electrons for catalysis and chemical reactions than their solid counterparts. [11][12][13][14][15][16] Therefore, using metals in their liquid state, enables efficient liquid interface reactions, which provides tremendous opportunities in chemical synthesis. Though still in its infancy, this approach has already gained signicant interest considering their use as specic reaction media for material synthesis and catalytic processes and has rapidly developed over the past decade.…”