Here, we present oxygen-deficient black ZrO2−x as a new material for sunlight absorption with a low band gap around ~1.5 eV, via a controlled magnesiothermic reduction in 5% H2/Ar from white ZrO2, a wide bandgap(~5 eV) semiconductor, usually not considered for solar light absorption. It shows for the first time a dramatic increase in solar light absorbance and significant activity for solar light-induced H2 production from methanol-water with excellent stability up to 30 days while white ZrO2 fails. Generation of large amounts of oxygen vacancies or surface defects clearly visualized by the HR-TEM and HR-SEM images is the main reason for the drastic alteration of the optical properties through the formation of new energy states near valence band and conduction band towards Fermi level in black ZrO2−x as indicated by XPS and DFT calculations of black ZrO2−x. Current reduction method using Mg and H2 is mild, but highly efficient to produce solar light-assisted photocatalytically active black ZrO2−x.

Progress in several important electrochemical technologies, including batteries, fuel cells, sensors, and electrosynthesis, is currently materials-limited. A common feature of all electrode reactions is the imbalance (i.e., loss or generation) of ions at the electrode surface. We describe in this paper a method by which excess ions in the electrode diffusion layer can be imaged, and used to identify the best electrode materials from a combinatorial array of compositions.Although in principle this method can be applied to many electrochemical problems, we have focused on finding better electrocatalysts for direct methanol fuel cells (DMFCs). The DMFC performs two half-cell reactions: oxidation of methanol, and reduction of oxygen. Two of the most important problems in DMFCs are the poor performance of the electrocatalysts, and the crossover of methanol from the anode to the cathode side of the cell. An ideal situation would be the simultaneous development of two new catalysts: an anode that oxidizes methanol at low overpotential, and a “methanol-tolerant” cathode that reduces oxygen without oxidizing methanol.Based on previously developed rules for predicting the activity of ternary alloy catalysts (Ley, et al., J. Electrochem. Soc. 1997, 144, 1543), we began searching quaternary combinations of noble metals for the anode, and ruthenium selenide-type materials for the cathode reaction. The anode and cathode reactions generate and consume protons, respectively, creating a substantial pH gradient at the electrode surface. Changes in local pH are imaged by means of an appropriate fluorescent indicator: Ni-PTP for the anode and Eosin Y for the cathode. DMFC testing confirms the utility of the screening method, in that a Pt/Ru/Os/Ir quaternary catalyst was substantially superior to the best binary and ternary catalysts prepared under similar conditions.

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This review outlines the fundamentals of active sites in biomimetic oxidase and M–N/C catalysts, responsible for carrying out oxygen reduction reaction at a very high TOF.

Fe-treated N-doped carbon prepared from polypyrrole in the presence of a ferric source employing a pyrolysis–leaching–stabilization synthesis protocol was found to show remarkable oxygen reduction activity.

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Porous carbons were prepared from a metal-organic framework (MOF, named ZIF-8), with or without modification, via high-temperature pyrolysis. Porous carbons with high nitrogen content were obtained from the calcination of MOF after introducing an ionic liquid (IL) (IL@MOF) via the ship-in-bottle method. The MOF-derived carbons (MDCs) and IL@MOF-derived carbons (IMDCs) were characterized using various techniques and used for liquid-phase adsorptions in both water and hydrocarbon to understand the possible applications in purification of water and fuel, respectively. Adsorptive performances for the removal of organic contaminants, atrazine (ATZ), diuron, and diclofenac, were remarkably enhanced with the modification/conversion of MOFs to MDC and IMDC. For example, in the case of ATZ adsorption, the maximum adsorption capacity of IMDC (Q = 208 m/g) was much higher than that of activated carbon (AC, Q = 60 m/g) and MDC (Q = 168 m/g) and was found to be the highest among the reported results so far. The results of adsorptive denitrogenation and desulfurization of fuel were similar to that of water purification. The IMDCs are very useful in the adsorptions since these new carbons showed remarkable performances in both the aqueous and nonaqueous phases. These results are very meaningful because hydrophobic and hydrophilic adsorbents are usually required for the adsorptions in the water and fuel phases, respectively. Moreover, a plausible mechanism, H-bonding, was also suggested to explain the remarkable performance of the IMDCs in the adsorptions. Therefore, the IMDCs derived from IL@MOF might have various applications, especially in adsorptions, based on high porosity, mesoporosity, doped nitrogen, and functional groups.

Nickel–iron based materials are well-known catalysts for the oxygen evolution reaction (OER) and have been widely investigated. However, the synergy between these two components is still controversial. Herein, we report a facile immersion method for the synthesis of binder-free nickel–iron hydroxide loaded on Ni foam (NiFe-OH/NF) with superior hydrophilic property and high OER catalytic activity. The strong hydrophilic property of the binder-free NiFe-OH/NF electrode significantly enhances an effective contact between electrocatalyst and aqueous electrolyte and favors the bubble detachment from the electrode, facilitating the electron transfer and improving the OER activity. The hydrophilic NiFe-OH/NF can achieve a geometrical current density of 100 mA cm–1 at an extremely low overpotential (219 mV), along with a Tafel slope of 56 mV dec–1 and superior long-term stability at high current density in alkaline media, strongly indicating that the hydrophilicity plays an important role in improving the OER performance in the NiFe-OH/NF.