Solar‐Driven Catalytic Urea Oxidation for Environmental Remediation and Energy Recovery

Abstract

The water-energy nexus is highly related to sustainable societal development. As one of the most abundant biowastes discharged into the environment, mild abatements and green conversions of urea wastewater have been widely investigated. Due to abundant sources, global distribution, and easy control, light-based catalytic strategies have become alternative on-site treatment approaches. After comprehensively surveying the recent progress, recent achievements of urea oxidation under light irradiation are reviewed herein. Several typical lightpromoted systems employed in urea conversion, including photocatalysis, photo-electrocatalysis, photo-biocatalysis, and photocatalytic fuel cells, are meticulously introduced and discussed, from catalyst designs and medium conditions to established mechanisms. To realize the goal of sustainability, the chemical energy in urea-rich water could be utilized for the value-added production of hydrogen fuel and electricity. Finally, based on current developments, existing challenges are enumerated and developmental prospects in the future of lightdriven urea conversion technologies are proposed.

Indirect urea electrooxidation by nickel(III) in alkaline medium: From kinetic and mechanism to reactor modeling

“…Into the bulk, the anolyte is assumed to be perfectly stirred, and the urea concentration is therefore considered uniform in the bulk volume, Ω B . The macroscopic balance of urea can be written as Equation (32).…”

“…Furthermore, by combining the newly established kinetic rate law with the electrolysis results obtained at high urea conversion rates, a detailed mechanism of urea oxidation in alkaline medium on nickel(III) active sites was proposed, allowing the formation of the liquid phase byproducts identified by Tatarchuk et al 25 and also in our previous work. 30 Finally, one can regret a lack of Electrochemical Engineering approach of the UEO processes (cell design, geometry and optimization at pilot and industrial scale) 31,32 in the state of the art. The present study proposes an original approach enabling the coupled phenomena (electrooxidation, adsorption, kinetic and mass transport) that occurs during the UEO process to be described.…”

Energy storage mechanism, advancement, challenges, and perspectives on vivid manganese redox couples

“…The iron redox couples are the most appealing candidates for RFBs owing to their low cost, ecofriendliness, non-toxicity, high solubility, abundance, and steady electrochemical reversibility. For instance, various iron-based RFBs have been proposed over the past decades such as Fe/Cr, 56 Fe/V, 57 Fe/Cd, 58 Fe/Pb, 59 all iron, 60 and Zn/Fe 61 RFBs, respectively. However, every system has its own critical issues which need to be addressed.…”

Designing bifunctional catalysts for urea electrolysis: progress and perspectives

“…Also, human/animal excrement contains a high level of urea, and the improper discharge of such urea-rich effluents leads to serious environmental pollution issues (e.g., eutrophication and NO x gaseous pollutants) and a waste of nitrogen resources. [4][5][6][7] Therefore, a green strategy toward the processing of urea-rich effluents would alleviate the related environmental problems and accelerate the global nitrogen cycle. 8 Recently, the electrooxidation of urea, which can convert urea into CO 2 , N 2 , and water in an efficient manner, under mild conditions has gained increasing interest.…”