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The phase transformation of catalysts has been extensively observed in heterogeneous catalytic reactions that hinder the long cycling catalysis, and it remains a big challenge to precisely control the active phase during the complex conditions in electrochemical catalysis. Here, we theoretically predict that carbon-based support could achieve the phase engineering regulation of catalysts by suppressing specific phase transformation. Taken single-walled carbon nanotube (SWCNT) as typical support, combined with calculated E-pH (Pourbaix) diagram and advanced synchrotron-based characterizations technologies prove there are two different active phases source from cobalt selenide which demonstrate that the feasibility of using support effect regulating the potential advantageous catalysts. Moreover, it is worth noting that the phase engineering derived Co3O4-SWCNT exhibits a low overpotential of 201 mV for delivering the current density of 10 mA/cm2 in electrocatalytic oxygen evolution reaction (OER). Also, it reaches a record current density of 529 mA/cm2 at 1.63 V (vs. RHE) in the electrocatalytic urea oxidation reaction (UOR), overwhelming most previously reported catalysts.

Despite acknowledgment of structural reconstruction of materials following oxygen evolution reaction (OER) reaction, the role of support during the reconstruction process has been ignored. Given this, we directly in situ transform the residual iron present in raw single-walled carbon nanotubes (SWCNT) into Fe2O3 and thus build Fe2O3-CNT as the model system. Intriguingly, an anomalous self-optimization occurred on SWCNT and the derived components show satisfactory electrochemical performance. Soft X-ray absorption spectroscopy (sXAS) analysis and theory calculation correspondingly indicate that self-optimization yields stronger interaction between SWCNT and Fe2O3 nanoparticles, where the electrons migrate from Fe2O3 to optimized SWCNT. Such polarization will generate a positive charge center and thus boost the OER activity. This finding directly observes the self-optimization of support effect, providing a new perspective for OER and related electrochemical reactions.

Broadly, the oxygen evolution reaction (OER) has been deeply understood as a significant part of energy conversion and storage. Nevertheless, the anions in the OER catalysts have been neglected for various reasons such as inactive sites, dissolution, and oxidation, amongst others. Herein, we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap. The advanced operando synchrotron radiation Fourier transform infrared (SR-FTIR) spectroscopy, synchrotron radiation photoelectron spectroscopy (SRPES) depth detection and differential X-ray absorption fine structure (Δ-XAFS) spectrum jointly point out that some oxidized sulfur species (SO42−) will self-optimize new Ni–S bonds during OER process. Such amazing anionic self-optimization (ASO) behavior has never been observed in the OER process. Subsequently, the optimization-derived component shows a significantly improved electrocatalytic performance (activity, stability, etc.) compared to reference catalyst Ni(OH)2. Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst, and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER, respectively. This work demonstrates the vital role of anions in the electrochemical process, which will open up new perspectives for understanding OER and provide some new ideas in related fields (especially catalysis and chemistry).

Electrocatalysis is recognized as a significant process for energy conversion. In fact, numerous factors, including the variable electronic structure of electrocatalysts, rich intermediates, and mutable active phases, have important but complex influences on the catalytic process. In addition, the support of electrocatalysts is considered as one of key factors that correlate to the final catalytic performance. In this Perspective, some recent advances regarding the support effects in electrocatalysis are briefly summarized. Synchrotron radiation-based characterizations are introduced to reveal the support-induced modulation in electrocatalysts. Recent in situ/operando studies are emphasized for better understanding of the real interaction between catalysts and support, together with visualizing the dynamic catalytic process. Some perspectives are proposed that may accelerate more attention being given to the support's optimization for future practical applications.

Electrocatalytic water splitting have demonstrated an established methodology to generate hydrogen of high purity, attracting lots of attention from industry. However, deficient supplies or poor electrochemical stability of catalysts contributes to unsatisfactory electrocatalytic hydrogen production, particularly while maintaining high current densities. Herein, we develop a robust catalyst by directly phosphating raw single-walled carbon nanotube films which can be self-optimized into O-FePx-SWCNT, P-Fe2O3-SWCNT or P-FeOOH-SWCNT catalysts, depending on the selected electrolytes with different pH values. The electrochemical measurements reveal the excellent electrocatalytic performance of catalytic films in a wide pH range. Notably, there is no observable degradation, even following one-week of continuous electrolysis process, which reached an elevated current density of 125 mA/cm2 at neutral conditions. In order to manifest its cogent applications, the catalyst is employed to stably electrolyze lake water, further indicating potential hydrogen production in inland areas. Our work confirms the feasibility of using structural self-optimization engineering to develop desirable electrocatalysts, providing flexible catalytic films for practical applications and answering the long-standing controversial question about active sites based on X-ray absorption fine structure (XAFS), operando synchrotron radiation Fourier transform infrared (SR-FTIR) spectroscopy and theoretical calculations, which will significantly contribute to the advancement of HER-related basic and applied research.

Flower-like MoS2 spheres were successfully prepared via a facile hydrothermal method. The effects of excess sulfur on the formation of MoS2 were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The XRD pattern showed that the preferential orientation of the flower-like hexagonal 2H–MoS2 spheres was the (002) plane, and I002/I100 ratio values indicated that the (002) plane grew more completely than the (100) plane with increasing S/Mo ratio. The FESEM images revealed that the sheet thickness of the MoS2 spheres increased to ~30 nm with increasing S/Mo ratio, exposing more edges on the nanosheets of the MoS2 spheres. Photocatalytic properties of the products were studied, and the results showed that the MoS2 sample with a S/Mo ratio of 2.75 exhibited the highest degradation rate constant and methylene blue degradation rate under 90 min visible light irradiation. The results showed that the enhancement of photocatalytic activity originated from increasing exposed area of the {100} facets with increasing S/Mo ratio under the hydrothermal environment.

A simple low-temperature solid-state reaction in the presence of the surfactant PEG400 was developed to obtain ZnO/CdS nanocomposites. The effects of synthesis temperature and reaction time on crystal structure and optical properties of the nanocomposites were investigated by several technologies. X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) characterizations showed that the products consisted of the nanoparticles, and the grain growth kinetics of the cubic CdS and the hexagonal ZnO phase in the nanocomposites was described. The mechanism analysis suggested that sufficient grinding and heating treatment was a key to form the ZnO/CdS nanocomposites, and the surfactant PEG400 was proved not to involve the reaction and prevent the nanoparticles from aggregating to larger in whole grinding and heat-treatment process. Ultraviolet–visible (UV–vis) spectra revealed that the band gaps of the nanocomposites could be tuned by the reaction temperature and reaction time. Photoluminescence (PL) spectra showed that the changing position and the intensity of the emission peaks resulted from the rate of electron transfer and recombination probability under the different conditions.