The meticulous design of advanced electrocatalysts and their integration into gas diffusion electrode (GDE) architectures is emerging as a prominent research paradigm in the H 2 O 2 electrosynthesis community. However, it remains perplexing that electrocatalysts and assembled GDE frequently exhibit substantial discrepancies in H 2 O 2 selectivity during bulk electrolysis. Here, we elucidate the pivotal role of mass transfer behavior of key species (including reactants and products) beyond the intrinsic properties of the electrocatalyst in dictating electrode-scale H 2 O 2 selectivity. This tendency becomes more pronounced in high reaction rate (current density) regimes where transport limitations are intensified. By utilizing diffusion-related parameters (DRP) of GDEs (i.e., wettability and catalyst layer thickness) as probe factors, we employ both short- and long-term electrolysis in conjunction with in-situ electrochemical reflection-absorption imaging and theoretical calculations to thoroughly investigate the impact of DRP and DRP-controlled local microenvironments on O 2 and H 2 O 2 mass transfer. The mechanistic origins of diffusion-dependent conversion selectivity at the electrode scale are unveiled accordingly. The fundamental insights gained from this study underscore the necessity of architectural innovations for mainstream hydrophobic GDEs that can synchronously optimize mass transfer of reactants and products, paving the way for next-generation GDEs in gas-consuming electroreduction scenarios.
Zhenglin Chen,Guangzhen Liu,Shuiping Yu,Lixia Yang,Lingyi Zheng,Zhihui Wei,Shenglian Luo
Cathode materials with high hydrogen peroxide (H 2 O 2 ) selectivity and Fe 2+ regeneration under macroneutral conditions are the essential for practical electro-Fenton processes. Herein, we develop an amorphous cobalt sulphide (CoSx(t = x)@Cu) cocatalytic electro-Fenton (EF) system capable of effectively degrading organic pollutants, such as sulfamethoxazole, at macroneutral pH conditions. Owing to the flexible electronic properties of amorphous structures and charge redistribution triggered by S defects, the optimum CoSx(t = 8)@Cu cathode successfully introduces H*/H + and promotes the in-situ evolution of H 2 O 2 . Additionally, an acidic microenvironment was constructed on the CoSx(t = 8)@Cu surface by the unreduced H*/H + , enabling a self-adjustment from alkalinity to acidity in the EF reaction without adding acid. Such self-adjustment effectually inhibits iron sludge production and promotes Fe 2+ regeneration, assuring 80% Fe 2+ cycling efficiency. More importantly, the EF system possesses outstanding stability and applicability for organic pollutant remediation regardless of water matrices. This work elucidates the intrinsic mechanism of amorphous electrocatalysts in overcoming the pH limitation of EF reactions, extending the applicability of Fenton technology.
At present, over 95 % of H 2 O 2 is produced via the anthraquinone process that requires large infrastructure, generates organic pollution, and poses safety issues. Electrochemical H 2 O 2 generation through oxygen reduction can serve as an alternative, reliable, and decentralized production method if affordable and high-performance electrocatalysts can be developed. Herein, a two-step process is used to prepare an Fe-based complex as a non-precious metal electrocatalyst to facilitate oxygen reduction reaction (ORR) and produce an alkaline H 2 O 2 solution. The Fe complex of benzene-1,3,5-tricarboxylate (FeBTC) is first synthesized using a hydrothermal method and then activated via a pulsed laser treatment process that is optimized via the Taguchi method. The pulse-laser-treated FeBTC (PL-FeBTC) lowers the H 2 O 2 electrosynthesis overpotential by 50 mV at −0.1 mA/cm 2 and exhibits a 25 % increase in H 2 O 2 product selectivity at 0.4 V vs. RHE. The experimental results indicate that the O 2 -to-H 2 O 2 turnover frequency and electrocatalytic yield of the Fe-based metal–organic framework are enhanced simultaneously through solid-to-solid pulsed laser conversion. Through a series of X-ray photoelectron spectroscopy, elemental analysis, Raman spectroscopy, X-ray absorption spectroscopy, and control atmospheric experiments, the origin of the improvement in catalytic performance is rationalized through the formation of an oxo-bridge across the di–Fe active site via an oxygen-doping mechanism, thus providing a systematic laser methodology for precise structure-performance tuning. Beyond H 2 O 2 generation, this study further lays the foundation for the development of cost-effective and scalable electrocatalysts that are central to other commodity manufacturing and sustainable resourcification processes.
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