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To fabricate high-quality catalysts with abundant active sites, a series of transition-metal-modified nitrogenous carbon catalysts (Ta-NOC, Nb-NOC, and Nb/Ta-NOC) was successfully fabricated via pyrolysis and ion exchange. Owing to the high conductivity and ion transport capacity of its unique nitrogen-carbon structure, and synergistic effect of dual-metal active sites on modulating electronic structure, Nb/Ta-NOC catalyst exhibited an excellent catalytic performance and a remarkable electrochemical stability in triiodide reduction reaction (IRR) and hydrogen evolution reaction (HER). Nb/Ta-NOC catalyst achieved an ideal conversion efficiency of 8.45% for IRR in solar cells, which was higher than that of Pt electrode (7.63%). Furthermore, Nb/Ta-NOC catalyst exhibited a small overpotential of 145 mV at a current density of 10 mA·cm-2 and a Tafel slope of 77 mV dec-1 for HER. This work provided a new approach for the rational design of the active-sites-rich electrocatalysts for energy conversion applications.

Developing electrocatalysts with excellent catalytic performance and superior durability for hydrogen evolution reaction (HER) remains a challenge. Herein, metal-nitrogen sites (M–Nx, M = Ni and Cu) are successfully implanted into zeolitic imidazolate zinc framework (ZIF-8)-derived nitrogen-doped porous carbon (ZIF/NC) to prepare Ni-ZIF/NC and Cu-ZIF/NC electrocatalysts for the HER. These M–Nx active sites significantly enhanced the electrocatalytic activities of Ni-ZIF/NC and Cu-ZIF/NC. Metal Ni acted as a catalyst for catalysis of Ni-ZIF/NC to form carbon nanotubes-like structures, which provided convenient ion transmission pathways. Owing to its special morphology and an increased number of defects, Ni-ZIF/NC displayed superior electrocatalytic activity in the HER compared to those of Cu-ZIF/NC and ZIF/NC. In an alkaline environment, Ni-ZIF/NC exhibited an overpotential at the current density of 10 mA cm−2 (η10) of 163.0 mV and Tafel slope of 85.0 mV dec−1, demonstrating an electrocatalytic property equivalent to that of Pt/C. In an acidic environment, Ni-ZIF/NC yielded a η10 of 177.4 mV and Tafel slope of 83.9 mV dec−1, which were comparable to those of 20 wt.% Pt/C. Moreover, Ni-ZIF/NC and Cu-ZIF/NC also exhibited superior stabilities in alkaline environments. This work offers a valuable strategy for controlling the morphology and implanting M–Nx active sites into carbon for designing novel catalysts for use in alternative new energy applications.

Development of low-cost and efficient photocatalytic materials with visible-light response is of urgent need for solving energy and environmental problems. Here, a metal-free two-dimensional (2D) π-conjugated hybrid g-C3N4 photocatalyst with tunable band structure was prepared by a novel one-pot bottom-up method based on a supersaturated precipitation process of urea and triethanolamine (TEOA) solution. The microstructure of the hybrid g-C3N4 is revealed to be a compound of periodic tri-s-triazine units grafted with N-doped graphene (GR) fragments. From experimental evidence and theoretical calculations, the two different π-conjugated fragments in the hybrid g-C3N4 material are proved to construct a 2D in-plane junction structure, thereby expanding the light absorption range and accelerating the interface charge transfer. The π-conjugated electron coupling in the 2D photocatalyst eliminates the grain boundary effect, and the coupled highest occupied molecular orbital (HOMO) effectively promotes the separation of photo-induced charge carriers. Compared with the g-C3N4 prepared by the conventional method, the visible-light H2 production activity of the optimized sample is enhanced by 253 %. This work provides a new strategy of constructing metal-free g-C3N4 hybrids for efficient photocatalytic water splitting.

In the research of photocatalysis, the effect of mass transfer has been seriously ignored, though its importance to photocatalytic performance has been already proved. In this work, self-propelled jet carbon micromotors, carbon bottle (CB), are combined with photocatalysts to enhance the photocatalytic performance, based on the infrared light utilization and active mass flow transfer, the so-called “on-the-fly” working mode. Compared with the traditional Janus motors, the environmentally friendly CB motors, which can be prepared through one-step hydrothermal route, has the advantages of simple synthesis, low price and not containing precious metal. The CB motor has excellent motion characteristics in pure water without additional chemicals as fuels. The photocatalytic activity of 10 wt% CB/g-C3N4 and 10 wt% CB/P25 are 2.1 and 2.3 times than that of pure g-C3N4 and P25, respectively. This work provides a new strategy for the development of photocatalytic technology by utilizing the self-propulsion of micromotors.

Energy and mass transfer in photocatalytic systems plays a significant role in photocatalytic water splitting, but relevant research has long been ignored. Here, an interfacial photocatalytic mode for photocatalytic hydrogen production is exploited to optimize the energy and mass flows and mainly includes a heat-insulating layer, a water-channel layer, and a photothermal photocatalytic layer. In this mode, the energy flow is optimized for efficient spreading, conversion, and utilization. A low-loss path (ultrathin water film) and an efficient heat localized zone are constructed, where light energy, especially infrared-light energy, can transfer to the target functional membrane surface with low loss and the thermal energy converted from light can be localized for further use. Meanwhile, the optimization of the mass flow is achieved by improving the desorption capacity of the products. The generated hydrogen bubbles can rapidly leave from the surface of the photocatalyst, along with the active sites being released timely. Consequently, the photocatalytic hydrogen production rate can be increased up to about 6.6 times that in a conventional photocatalytic mode. From the system design aspect, this work provides an efficient strategy to improve the performance of photocatalytic water splitting by optimizing the energy and mass flows.

The development of low-cost and high-active cocatalysts is one of the most significant links for photocatalytic water splitting. Herein, a novel strategy of electron delocalization modulation for transition metal sulfides has been developed by anion hybridization. P-modified CoS2 (CoS2∣P) nanocrystals were firstly fabricated via a gas-solid reaction and coupled with CdS nanorods to construct a composite catalyst for solar H2 evolution reaction (HER). The CdS/CoS2∣P catalyst shows an HER rate of 57.8 µmol·h−1, which is 18 times that of the bare CdS, 8 times that of the CdS/CoS2, and twice that of Pt/CdS. The reduced energy barrier and suppressed reverse reaction for HER on the catalyst have been predicted and explained by density functional theory (DFT) calculation. The underlying design strategy of novel cocatalysts by electron delocalization modulation may shed light on the rational development of other advanced catalysts for energy conversion.

A new kind of intermetallic compounds (IMC) were found around copper pillar in micron level bumps. To investigate the formation mechanism, three different sized Sn/Ni/Cu bumps (10 μm, 20 μm, 50 μm) were electroplated then reflowed at 230 °C for 100 s. After reflow process, a thin layer of IMC was formed around copper pillar, which is attributed to surface wetting behavior. After aging at 170 °C and 200 °C for different times, the growth mechanism of sidewall IMC was observed by scanning electron microscopy combined with electron backscatter diffraction (EBSD) technology. Surface diffusion was considered to be the main driving force for sidewall IMC growth for the activation energy of them was found to be much smaller than that in previous studies. The EBSD results showed a preferred orientation of sidewall Cu3Sn grains being perpendicular to copper periphery, which indicated direction of Cu atoms flux during Cu3Sn growth. Formation mechanism of this novel sidewall IMC was proposed based on surface wetting and surface diffusion. The findings contribute to the failure mechanism study in small size bumps and provide insights into the reliability of 3D electronic packaging.

Developing highly-efficient multifunctional electrocatalysts for energy conversion devices is of great importance. A sequence of nano-sized bimetal (Al, Cr, Fe) niobium oxide nanoparticles anchored on aloe peel-derived porous carbon skeleton hybrids (AN/APPC, CN/APPC, and FN/APPC) are successfully prepared via co-precipitation avenue and used as electrocatalysts for photovoltaics and alkaline hydrogen evolution reaction. Benefiting from the synergies between nano-sized metal niobium oxides and highly conductive porous carbon skeleton, these robust polycomponent hybrid electrocatalysts exhibit superior catalytic performances for accelerating the triiodide reduction and hydrogen evolution reaction. The solar cell with AN/APPC electrocatalyst achieves an outstanding device efficiency of 7.31%, superior to that with Pt (6.84%), and the AN/APPC electrocatalyst exhibit an overpotential (131.6 mV) when the current density is 10 mA cm−2 and Tafel slope (54 mV dec−1) in 1 M KOH for hydrogen evolution reaction. The AN/APPC electrocatalysts illustrate remarkable electrochemical durability in both I3−/I− electrolyte and alkaline media. Furthermore, the catalytic mechanism was clarified both from the electronic structure and work function through first-principle density functional theory (DFT) calculations. This work opens a new avenue for electrocatalysis field via using nano-sized porous bio-carbon skeleton loaded with niobium-based binary metal.

The elaborate design of electrode materials plays a critical role in developing high-performance supercapacitors. In the present work, a convenient avenue is adopted to adjust the supercapacitive behavior of carbon-based electrodes by incorporating transition metals (Co, Nb, Mo, and Fe) into Co/Zn-ZIF derived nitrogen-doped porous carbon (NDPC). The experiment results demonstrated that incorporating transition metal species tuned the microstructure, nanoporous textures, and hydrophilicities of as-prepared Co-NDPC and M/Co-NDPC (M = Nb, Mo, or Fe), which further tailored their supercapacitive performance. Owing to the higher surface area, abundant pores, and superior wettability of Nb/Co-NDPC sample, the corresponding electrode showed the highest specific capacitance of 293 F g−1 at 0.5 A g−1 with an outstanding capacitance retention of 82% at 20 A g−1. All the electrodes displayed remarkable stability over 15,000 charge–discharge cycles. The first-principle density functional theory (DFT) calculations revealed that the superior capacitive behaviors of Nb/Co-NDPC electrode could be attributed to the uneven electrostatic potential surface and robust K+ ion adsorption ability. This work provides an elaborate strategy for designing novel and high-performance electrode materials by adopting DFT calculations for supercapacitors.

Reduced graphene oxide (RGO) thin film was used to improve the performance of a low-temperature bonding process based on Cu microcones and Sn/Cu bumps (diameter: 25 μm), which has potential applications in high-density packaging. Under bonding conditions of a weight of 1500 g applied to each wafer for 10 min at a temperature of 120 °C, and incorporating a thin RGO layer, a compact bonding structure was obtained without interface voids. The RGO interlayer served as a barrier against interatomic diffusion of metals under zero applied pressure, and the formation of intermetallic compounds at the interface was thereby effectively reduced after bonding. Probable mechanisms for this bonding process are discussed. The investigation used standard 25 μm-diameter Sn/Cu bumps to simulate realistic industrial production.

Infrared light, more than 50% of the solar light energy, is long-termly ignored in the photocatalysis field due to its low photon energy. Herein, infrared-light-responsive photoinduced carriers driver is first constructed taking advantage of pyroelectric effect for enhancing photocatalytic hydrogen evolution. In order to give full play to its role, the photocatalytic reaction is localized on the surface and interface of the composite based on a new semi-immersion type heat collected photocatalytic microfiber system. The system is consisted of distinctive pyroelectric substrate poly(vinylidene fluoride-co-hexafluropropylene (PVDF-HFP), typical photothermal material carbon nanotube (CNT), and representative photocatalyst CdS. The transient photocurrent, electrochemical impedance spectroscopy, time-resolved photoluminescence and pyroelectric potential characterizations indicate that the infrared-light-responsive carriers driver significantly promotes the photogenerated charge separation, accelerates carrier migration, and prolongs carrier lifetime. The photocatalytic hydrogen evolution efficiency is remarkably improved more than five times with the highest average apparent quantum yield of 16.9%. It may open up new horizons to photocatalytic technology for the more efficient use of infrared light.

A non-uniform copper oxide layer with several hundred nanometers thick was observed covering the surface of 10 μm-diameter Cu/SnAg microbump. Tin whiskers were also found to form on the weak spots of this copper oxide layer, where were localized stress relief centers. The HRTEM results reveal the existence of twin grain boundary between tin whisker and neighboring grain. Numerous dislocations at the twin boundary provide paths for the tin atoms to slip into tin whisker. It is the first time that the existence of copper oxide layer and the relationship between copper oxide layer and tin whiskers growth was studied and revealed in micron-level bumps. This present study has significant meaning for 3D electronic packaging as small size microbumps become increasingly prevalent and in which, surface diffusion becomes more important.

Two issues are required to be solved to bring intrinsically self-healing polymer coatings into real applications: remote activation and satisfied practical properties. Here, we used MXene, a newly reported two-dimensional material, to provide an epoxy coating with light-induced self-healing capabilities and we worked to enhance the properties of that coating. The self-healing coatings had a reversible crosslinking network based on the Diels-Alder reaction among maleimide groups from bis(4-maleimidopheny)methane and dangling furan groups in oligomers that were prepared through the condensation polymerization of diglycidylether of bisphenol A and furfurylamine. The results showed that the delaminated MXene flakes were small in size, around 900 nm, and dispersed well in self-healing coatings. The MXene flakes of only 2.80 wt % improved greatly the pencil hardness of the coating hardness from HB to 5H and the polarization resistance from 4.3 to 428.3 MΩ cm−2. The self-healing behavior, however, was retarded by MXene flakes. Leveling agent acted a key part here to facilitate the gap closure driven by reverse plasticity to compensate for the limitation of macromolecular mobility resulting from the MXene flakes. The self-healing of coatings was achieved in 30 s by thermal treatment at 150 °C. The efficient self-healing was also demonstrated based on the recovery of the anti-corrosion capability. MXene flakes also played an evident photothermal role in generating heat via irradiation of near-infrared light at 808 nm and focused sunlight. The healing can be quickly obtained in 10 s under irradiation of near-infrared light at 808 nm having a power density of 6.28 W cm−2 or in 10 min under irradiation of focused sunlight having a power density of 4.0 W cm−2.