Electro-generative hydrogenation of allyl alcohol applying PEM fuel cell reactor

Fuel Cell Reactors for the Clean Cogeneration of Electrical Energy and Value-Added Chemicals

Fuel cell reactors can be tailored to simultaneously cogenerate value-added chemicals and electrical energy while releasing negligible CO2 emissions or other pollution; moreover, some of these reactors can even “breathe in” poisonous gas as feedstock. Such clean cogeneration favorably offsets the fast depletion of fossil fuel resources and eases growing environmental concerns. These unique reactors inherit advantages from fuel cells: a high energy conversion efficiency and high selectivity. Compared with similar energy conversion devices with sandwich structures, fuel cell reactors have successfully “hit three birds with one stone” by generating power, producing chemicals, and maintaining eco-friendliness. In this review, we provide a systematic summary on the state of the art regarding fuel cell reactors and key components, as well as the typical cogeneration reactions accomplished in these reactors. Most strategies fall short in reaching a win–win situation that meets production demand while concurrently addressing environmental issues. The use of fuel cells (FCs) as reactors to simultaneously produce value-added chemicals and electrical power without environmental pollution has emerged as a promising direction. The FC reactor has been well recognized due to its “one stone hitting three birds” merit, namely, efficient chemical production, electrical power generation, and environmental friendliness. Fuel cell reactors for cogeneration provide multidisciplinary perspectives on clean chemical production, effective energy utilization, and even pollutant treatment, with far-reaching implications for the wider scientific community and society. The scope of this review focuses on unique reactors that can convert low-value reactants and/or industrial wastes to value-added chemicals while simultaneously cogenerating electrical power in an environmentally friendly manner.

Graphical Abstract

A schematic diagram for the concept of fuel cell reactors for cogeneration of electrical energy and value-added chemicals

Electrocatalytic Hydrogenation of Biomass-Derived Organics: A Review

Sustainable energy generation calls for a shift away from centralized, high-temperature, energy-intensive processes to decentralized, low-temperature conversions that can be powered by electricity produced from renewable sources. Electrocatalytic conversion of biomass-derived feedstocks would allow carbon recycling of distributed, energy-poor resources in the absence of sinks and sources of high-grade heat. Selective, efficient electrocatalysts that operate at low temperatures are needed for electrocatalytic hydrogenation (ECH) to upgrade the feedstocks. For effective generation of energy-dense chemicals and fuels, two design criteria must be met: (i) a high H:C ratio via ECH to allow for high-quality fuels and blends and (ii) a lower O:C ratio in the target molecules via electrochemical decarboxylation/deoxygenation to improve the stability of fuels and chemicals. The goal of this review is to determine whether the following questions have been sufficiently answered in the open literature, and if not, what additional information is required:(1)What organic functionalities are accessible for electrocatalytic hydrogenation under a set of reaction conditions? How do substitutions and functionalities impact the activity and selectivity of ECH?(2)What material properties cause an electrocatalyst to be active for ECH? Can general trends in ECH be formulated based on the type of electrocatalyst?(3)What are the impacts of reaction conditions (electrolyte concentration, pH, operating potential) and reactor types?

Effects of hydrophobicity of diffusion layer on the electroreduction of biomass derivatives in polymer electrolyte membrane reactors

For the first time, the hydrophobicity design of a diffusion layer based on the volatility of hydrogenation reactants in aqueous solutions is reported. The hydrophobicity of the diffusion layer greatly influences the hydrogenation performance of two model biomass derivatives, namely, butanone and maleic acid, in polymer electrolyte membrane reactors operated at atmospheric pressure. Hydrophobic carbon paper repels aqueous solutions, but highly volatile butanone can permeate in vapor form and achieve a high hydrogenation rate, whereas, for nonvolatile maleic acid, great mass transfer resistance prevents hydrogenation. With a hydrophilic stainless-steel welded mesh diffusion layer, aqueous solutions of both butanone and maleic acid permeate in liquid form. Hydrogenation of maleic acid reaches a similar level as that of butanone. The maximum reaction rate is 340 nmol cm(-2)  s(-1) for both hydrogenation systems and the current efficiency reaches 70 %. These results are better than those reported in the literature.