Hydrogen is a clean fuel for transportation and energy storage. It has several attractive features, including a higher energy content by weight, use in fuel cells that produces only water as a by-product, storage in small and large quantities by various methods, and established transportation and infrastructures. A hydrogen economy consists of three steps, i.e., hydrogen production, storage, and applications. All three steps involved in a hydrogen economy can be divided into catalytic and non-catalytic approaches. For catalytic processes, the efficiency highly depends on the type and physico-chemical characteristics of the catalysts. Therefore, for the improvement of these catalytic processes, the development of highly efficient and stable catalysts is highly required.

Catalytic Hydrogen Production, Storage and Application

Hydrogen, undoubtedly the next‐generation fuel for supplying the world's energy demands, needs economically scalable bifunctional electrocatalysts for its sustainable production. Non‐noble transition metal‐based electrocatalysts are considered an economic solution for water splitting applications. A single‐step solid‐state approach for the economically scalable transformation of Ni‐based substrates into single‐crystalline nickel sulfide nanoplate arrays is developed. X‐ray diffraction and transmission electron microscopy measurements reveal the influence of the transformation temperature on the crystal growth direction, which in turn can manipulate the chemical state at the catalyst surface. Ni‐based sulfide formed at 450 °C exhibits an enhanced concentration of electrocatalytically‐active Ni3+ at their surface and a reduced electron density around sulfur atoms, optimal for efficient H2 production. The Ni‐based sulfide electrocatalysts display exceptional electrocatalytic performance for both oxygen and hydrogen evolution, with overpotentials of 170 and 90 mV respectively. Remarkably, the two‐electrode cell for overall electrolysis of alkaline water demonstrates an ultra‐low cell potential of 1.46 V at 10 mA cm−2 and 1.69 V at 100 mA cm−2. In addition to the exceptionally low water‐splitting cell voltage, this self‐standing electrocatalyst is of binderfree nature, with the electrode preparation being a low‐cost and single‐step process, easily scalable to industrial scales.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/smtd.202200181

Single‐Step Solid‐State Scalable Transformation of Ni‐Based Substrates to High‐Oxidation State Nickel Sulfide Nanoplate Arrays as Exceptional Bifunctional Electrocatalyst for Overall Water Splitting

Intercalation of coordination polymer to regulate interlayer of 2D layered MoS2 for hydrogen evolution reaction

Production of chlorine

The development of a new type of oxygen evolution reaction (OER) catalyst to reduce the energy loss in the process of water electrolysis is of great significance to the realization of the industrialization of hydrogen energy storage. Herein, we report the catalysts of NiFe double-layer hydroxide (NiFe-LDH) mixed with different equivalent terephthalic acid (TPA), synthesized by the hydrothermal method. The catalyst synthesized with the use of the precursor solution containing one equivalent of TPA shows the best performance with the current density of 2 mA cm−2 at an overpotential of 270 mV, the Tafel slope of 40 mV dec−1, and excellent stable electrocatalytic performance for OER. These catalysts were characterized in a variety of methods. X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), and Raman spectrum proved the presence of TPA in the catalysts. The lamellar structure and the uniform distribution of Ni and Fe in the catalysts were observed by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). In X-ray photoelectron spectroscopy (XPS) of NiFe-LDH with and without TPA, the changes in the peak positions of Ni and Fe spectra indicate strong electronic interactions between TPA and Ni and Fe atoms. These results suggest that a certain amount of TPA can boost catalytic activity. 

/pdf/boosting-the-electrocatalytic-activity-of-nickel-iron-1qufqmb2.pdf

Boosting the Electrocatalytic Activity of Nickel-Iron Layered Double Hydroxide for the Oxygen Evolution Reaction byTerephthalic Acid

Of all the available resources given to mankind, the sunlight is perhaps the most abundant renewable energy resource, providing more than enough energy on earth to satisfy all the needs of humanity for several hundred years. Therefore, it is transient and sporadic that poses issues with how the energy can be harvested and processed when the sun does not shine. Scientists assume that electro/photoelectrochemical devices used for water splitting into hydrogen and oxygen may have one solution to solve this hindrance. Water electrolysis-generated hydrogen is an optimal energy carrier to store these forms of energy on scalable levels because the energy density is high, and no air pollution or toxic gas is released into the environment after combustion. However, in order to adopt these devices for readily use, they have to be low-cost for manufacturing and operation. It is thus crucial to develop electrocatalysts for water splitting based on low-cost and land-rich elements. In this review, I will summarize current advances in the synthesis of low-cost earth-abundant electrocatalysts for overall water splitting, with a particular focus on how to be linked with photoelectrocatalytic water splitting devices. The major obstacles that persist in designing these devices. The potential future developments in the production of efficient electrocatalysts for water electrolysis are also described.

M Sami

Papers

Earth-Abundant Electrocatalysts for Water Splitting: Current and Future Directions