Global-scale application of water-splitting technology for hydrogen fuel production and storage of intermittent renewable energy sources has called for the development of oxygen- and hydrogen-evolution catalysts that are inexpensive, efficient, robust, and can withstand frequent power interruptions and shutdowns. Here, we report the controlled electrodeposition of porous nickel–iron hydroxylphosphate (NiFe-OH-PO4) nanobelts onto the surface of macroporous nickel foams (NF) as a bifunctional electrocatalyst for efficient whole-cell water electrolysis. The NiFe-OH-PO4/NF electrode shows both high water oxidation and water reduction catalytic activity in alkaline solutions and is able to deliver current densities of 20 and 800 mA cm–2 at overpotentials of merely 249 and 326 mV for oxygen-evolution reaction, current densities of 20 and 300 mA cm–2 at overpotentials of only 135 and 208 mV for hydrogen-evolution reaction. Further, in a two-electrode water electrolytic cell, the bifunctional NiFe-OH-PO4/NF electrodes can obtain the current densities of 20 and 100 mA cm–2 at an overall cell potential of only 1.68 and 1.91 V, respectively. Remarkably, the NiFe-OH-PO4/NF catalyst also represents prolonged stability under both continuous and intermittent electrolysis and can be used for oxygen evolution and hydrogen evolution reversibly without degradation.Keywords: bifunctional catalyst; electrocatalysis; intermittent electrolysis; NiFe hydroxylphosphate composite; water reduction and water oxidation;

In order to achieve a perfect bottom-up electroplated Cu filling with a minimal surface thickness, 2-mercaptopyridine (2-MP) was investigated as a new leveler for replacing Janus Green B (JGB) for bottom-up copper filling. Electrochemical impedence results indicate that 2-MP has a stronger suppression for Cu deposition than JGB. With the addition of 2-MP, the filling capability of the electroplating solution is improved significantly with the Cu thickness on surface decreasing from ∼16 μm to ∼10 μm. The interaction mechanisms of 2-MP, bis(3-sulfopropyl) disulfide (SPS), Cl− and tri-block copolymer of PEG and PPG with ethylene oxide terminal blocks (EPE) in the plating solution are studied by galvanostatic measurements (GMs). The acceleration effect of SPS and the inhibition effect of 2-MP on copper deposition occur in the presence of EPE, and the convection-dependent adsorption (CDA) behavior of additives usually occurs with the injection of four additives at optional concentrations. Further, it was found that when 1.0 ppm 2-MP, 1.0 ppm SPS and 200 ppm EPE were injected into the basic electrolyte, the potential difference (Δh) value of the electrolyte became positive, and the bottom-up electroplated copper filling was obtained in the electrolyte in absence of Cl−. The interaction mechanisms of three additives for bottom-up filling have been investigated by GMs.

Three tetrazole derivatives (TDs), 1-(3-Acetamide) phenyl-5-mercaptotetrazole (ACET), 1-Phenyl-5-mercaptotetrazole (PMT) and 1-Methyl-5-mercaptotetrazole (MMT), have been studied as novel levelers for filling electroplated Cu microvia. It is found that the Cu deposition potential decreases with the addition of TDs into the Cu plating solutions, with the lowest deposition potential observed for MMT and the largest deposition potential change (Δη) observed for ACET. The ACET exhibits the strongest convection-dependent adsorption behavior with SPS, Cl−, and OP/OE, and the thickness of copper surface layer can be thinned to ∼15 μm in the ACET concentration range of 1.0 ∼ 10.0 ppm. The electrochemical impedance spectroscopy studies suggest that both the charge transfer resistance (Rct) and the adsorbed layer resistance (Rad) increase with the addition of TDs. Quantum chemical calculations indicate that the energy gaps (ΔE) of TDs correlate negatively with Δη, and the most active reaction sites for surface adsorption are the N3 in the thiol forms and the N4 in the thione forms of the TDs through Fukui functions.

A low environmental pollution etching system, MnO2–H2SO4–H3PO4–H2O colloid, was used to investigate surface etching performance of polycarbonate (PC) as a replacement for the chromic acid etching solution. The effects of H2SO4 concentrations, H3PO4 concentrations and etching times upon the surface topography, surface chemistry and surface roughness were studied. With the appropriate etching treatment, the surface average roughness (Ra) of PC substrates increased from 3 to 177 nm, and the adhesion strength between the electroless copper and PC substrate also reached 1.10 KN m−1. After the etching treatment, the PC surface became hydrophilic and the surface contact angle decreased from 95.2° to 24.8°. The intensity of C–O groups increased and the new functional groups (–COOH) formed on the PC surface with the etching treatment, which improved the adhesion strength between PC substrate and elctroless copper film.

In this paper, an environmentally friendly etching system containing MnO2–H3PO4–H2SO4 colloid was used to investigate surface etching for ABS- polycarbonate (PC/ABS) as a replacement for conventional chromic acid etching solutions. In order to obtain a good etching performance, a swelling system, containing tetramethylammonium hydroxide (TMAH), and 1-Methyl-2-pyrrolidinone (NMP), was used to investigate the surface swelling for PC/ABS resin. Then the effects of H2SO4 concentration, and etching time on the surface topographies and surface contact angle were investigated. After the optimal swelling and etching treatment, the surface contact angle of PC/ABS resin decreased from 95.7° to 28.3°, and the adhesion strength between electroless copper film and PC/ABS resin reached to 1.04 KN m−1. The FT-IR spectra and XPS analyses indicated that hydroxyl and carboxyl groups formed on the PC/ABS surface as a result of the swelling and etching treatment, which improved the adhesion strength between PC/ABS substrate and elctroless copper film.

The present study aimed to evaluate the surface etching of the acrylonitrile–butadiene–styrene (ABS) resin in the MnO2–H3PO4–H2SO4 colloid. To enhance the soluble Mn(IV) ion concentration and improve the etching performance of ABS resin, H3PO4 was added as a complexing agent into the MnO2–H2SO4 etching system. The effects of the H2SO4 concentration and etching time on the surface topography, surface roughness, adhesion strength, and the surface chemistry of the ABS substrates were investigated. The optimal oxidation potentials of MnO2 in the colloids decreased from 1.426 to 1.369 V with the addition of H3PO4. Though the etching conditions changed from 70 °C for 20 min to 60 °C for 10 min, the adhesion strength between the ABS substrates and electroless copper film increased from 1.19 to 1.33 KN/m after etching treatment. This could be attributed to the significant increase of the soluble Mn(IV) ion concentration in the MnO2–H3PO4–H2SO4 colloid. The surface chemistry results demonstrated that the oxidation reaction of −C═C– bonds in the polybutadiene phase was accelerated in the etching process by the addition of H3PO4, and the abundant −COOH and −OH groups were formed rapidly on the ABS surface with the etching treatment. These results were in agreement with the results of surface scanning electron microscopic observations and adhesion strength measurement. The results suggested that the MnO2–H3PO4–H2SO4 colloid was an effective surface etching system for the ABS surface roughness.

Bottom-up copper filling for different sub-micrometer trenches was investigated by electroless deposition technique using a PO-EO-PO triblock copolymer termed PEP-3100 as an additive. It was found that PEP-3100 (molecular weight 3100) had a strong inhibition for the electroless copper deposition. The bottom-up filling behavior of electroless copper bath for different trenches was investigated in a plating bath containing 1.0 mg l−1 PEP-3100. The cross-section SEM observation indicated the trenches with different widths ranging from 100 to 380 nm were all filled completely by electroless copper.

The bottom-up filling of electroless copper usually depends on inhibiting the Cu deposition at the surface or accelerating the Cu deposition in the bottom of trenches to achieve a relative high deposition rate of electroless copper in the bottom of trenches. In this paper, a complete bottom-up filling of electroless copper, in which the deposition rates of the electroless copper were not only inhibited at the surface of the substrate, but also were accelerated in the bottom of the trenched, was designed and achieved in the plating bath with an addition of bis (3-sulfopropyl) disulfide (SPS) and polyethylene glycol (PEG). The cross-sectional SEM observation of trenches indicated that all trenches with different widths ranging from 100 to 290 nm were filled completely by electroless copper, and no void was found. This was attributed to three factors, the electroless Cu deposition was accelerated markedly by an addition SPS only; but it was suppressed sharply by a combination addition SPS and PEG-4000; the large molecular weight and lower diffusion coefficient of PEG-4000 resulted in concentration gradient of PEG-4000 in the trenches. The effects of PEG-4000 and SPS on the polarization behaviors of the electroless copper plating bath were investigated by the linear sweep voltammetry method and mixed potential theory.

We investigated bottom-up electroless copper plating with addition of mercapto alkyl carboxylic acid (MACA) such as 3-mercapto-propionic acid (3-MPA), 11-mercapto-undecanoic acid (11-MUA), and 16-mercapto-hexadecanoic acid (16-MHA). The inhibition of copper plating deposition on the plane surface was observed with an addition of MACAs, and bottom-up fill was confirmed for MACAs with alkyl chain numbers of 3, 11, and 16. The bottom-up fill tendency was enhanced with increasing Alkyl chain number. This result strongly suggests that diffusion coefficient of inhibitor molecule plays an important role for bottom-up fill mechanisms, because MACA with longer alkyl chain has smaller diffusion coefficient than that with shorter alkyl chain.