Objective comparisons of electrocatalyst activity and stability using standard methods under identical conditions are necessary to evaluate the viability of existing electrocatalysts for integration into solar-fuel devices as well as to help inform the development of new catalytic systems. Herein, we use a standard protocol as a primary screen for evaluating the activity, short-term (2 h) stability, and electrochemically active surface area (ECSA) of 18 electrocatalysts for the hydrogen evolution reaction (HER) and 26 electrocatalysts for the oxygen evolution reaction (OER) under conditions relevant to an integrated solar water-splitting device in aqueous acidic or alkaline solution. Our primary figure of merit is the overpotential necessary to achieve a magnitude current density of 10 mA cm–2 per geometric area, the approximate current density expected for a 10% efficient solar-to-fuels conversion device under 1 sun illumination. The specific activity per ECSA of each material is also reported. Among HER...

Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices

Sunlight is by far the most plentiful renewable energy resource, providing Earth with enough power to meet all of humanity's needs several hundred times over. However, it is both diffuse and intermittent, which presents problems regarding how best to harvest this energy and store it for times when the sun is not shining. Devices that use sunlight to split water into hydrogen and oxygen could be one solution to these problems, because hydrogen is an excellent fuel. However, if such devices are to become widely adopted, they must be cheap to produce and operate. Therefore, the development of electrocatalysts for water splitting that comprise only inexpensive, earth-abundant elements is critical. In this Review, we investigate progress towards such electrocatalysts, with special emphasis on how they might be incorporated into photoelectrocatalytic water-splitting systems and the challenges that remain in developing these devices. Splitting water is an attractive means by which energy — either electrical and/or light — is stored and consumed on demand. Active and efficient catalysts for anodic and cathodic reactions often require precious metals. This Review covers base-metal catalysts that can afford high performance in a more sustainable and available manner.

Earth-abundant catalysts for electrochemical and photoelectrochemical water splitting

The conversion of sunlight into fuels and chemicals is an attractive prospect for the storage of renewable energy, and photoelectrocatalytic technologies represent a pathway by which solar fuels might be realized. However, there are numerous scientific challenges in developing these technologies. These include finding suitable materials for the absorption of incident photons, developing more efficient catalysts for both water splitting and the production of fuels, and understanding how interfaces between catalysts, photoabsorbers and electrolytes can be designed to minimize losses and resist degradation. In this Review, we highlight recent milestones in these areas and some key scientific challenges remaining between the current state of the art and a technology that can effectively convert sunlight into fuels and chemicals.

Materials for solar fuels and chemicals

Earth-abundant metals are attractive alternatives to the noble metal composite catalysts that are used in water electrolyzers based on proton-exchange membrane technology. Ni–Mo alloys have been previously developed for the hydrogen evolution reaction (HER), but synthesis methods to date have been limited to formation of catalyst coatings directly on a substrate. We report a method for generating unsupported nanopowders of Ni–Mo, which can be suspended in common solvents and cast onto arbitrary substrates. The mass-specific catalytic activity under alkaline conditions approaches that of the most active reported non-noble HER catalysts, and the coatings display good stability under alkaline conditions. We have also estimated turnover frequencies per surface atom at various overpotentials and conclude that the activity enhancement for Ni–Mo relative to pure Ni is due to a combination of increased surface area and increased fundamental catalytic activity.

/pdf/ni-mo-nanopowders-for-efficient-electrochemical-hydrogen-2c2sfq35so.pdf

Ni–Mo Nanopowders for Efficient Electrochemical Hydrogen Evolution

Splitting water to hydrogen and oxygen is a promising approach for storing energy from intermittent renewables, such as solar power. Efficient, scalable solar-driven electrolysis devices require active electrocatalysts made from earth-abundant elements. In this mini-review, we discuss recent investigations of homogeneous and heterogeneous hydrogen evolution electrocatalysts, with emphasis on our own work on cobalt and iron complexes and nickel-molybdenum alloys.

/pdf/earth-abundant-hydrogen-evolution-electrocatalysts-1laslczict.pdf

Earth-abundant hydrogen evolution electrocatalysts

Electrodeposited nickel-molybdenum, nickel-tungsten, cobalt-molybdenum, and cobalt-tungsten were characterized for the hydrogen evolution reaction (HER) in the electrolysis of 30 w/o KOH alkaline water at 25 C. The rate-determining step (rds) of the HER was suggested based on the Tafel slope of polarization and the capacitance of electrode-solution interface determined by ac impedance measurement. The HER on the nickel- and cobalt-based codeposits was enhanced significantly compared with that o the electrolytic nickel and cobalt with comparable deposit loadings. The decrease in the HER overpotential was more pronounced on the molybdenum-containing codeposits, particularly on cobalt-molybdenum which also showed a high stability. The enhancement of the HER was attributed to both the synergetic composition and the increased active surface of the codeposits. The real electrocatalytic activity of te electrodes and the effect of their and the increased active surface of the codeposits. The real electrocatalytic activity of the electrodes and the effect of their surface increase were distinguished quantitatively. The linear relations between HER overpotential and surface roughness factor of the electrodes on a Y-log(X) plot were obtained experimentally and interpreted based on the Tafel law.

https://iopscience.iop.org/article/10.1149/1.2054736/pdf

Study of Electrodeposited Nickel‐Molybdenum, Nickel‐Tungsten, Cobalt‐Molybdenum, and Cobalt‐Tungsten as Hydrogen Electrodes in Alkaline Water Electrolysis

Compressive stress is widely accepted as the driving force for tin whisker formation. There are several pathways for compressive stress buildup in Sn coatings, which include the following: residual stress generated during plating; stress formation due to interfacial reactions between tin and copper substrate; mechanical stress; and thermal mechanical stress due to coefficient of thermal expansion (CTE) mismatch between the tin layer and substrate during thermal cycling. In order to prevent or reduce whisker growth in tin deposits, compressive stress has to be eliminated or minimized. This paper discusses the pathways for compressive stress formation and various remedies for its elimination and minimization. Particularly, a novel approach for dealing with thermal mechanical stress due to CTE mismatch is discussed.

Driving force for the formation of Sn whiskers: compressive stress-pathways for its generation and remedies for its elimination and minimization

A printed wiring board (PWB) and a method of manufacturing the same. In one embodiment, the PWB includes: (1) a substrate having a conductive trace located thereon and (2) a multi-purpose finish including palladium alloy where palladium is alloyed with cobalt or a platinum group metal and is located on at least a portion of the conductive trace, which forms both a non-contact finish and a contact finish for the PWB.

Multi-purpose finish for printed wiring boards and method of manufacture of such boards

A method and composition for enhancing corrosion resistance, wear resistance, and contact resistance of a device comprising a copper or copper alloy substrate and at least one metal-based layer on a surface of the substrate. The composition comprises a phosphorus oxide compound selected from the group consisting of a phosphonic acid, a phosphonate salt, a phosphonate ester, a phosphoric acid, a phosphate salt, a phosphate ester, and mixtures thereof; an organic compound comprising a nitrogen-containing functional group; and a solvent having a surface tension less than about 50 dynes/cm as measured at 25°C.

Metallic surface enhancement

Compositions and methods for silver plating onto metal surfaces such as PWBs in electronics manufacture to produce a silver plating which is greater than 80 atomic % silver, tarnish resistant, and has good solderability.

Chonglun Fan

Papers

Study of Electrodeposited Nickel‐Molybdenum, Nickel‐Tungsten, Cobalt‐Molybdenum, and Cobalt‐Tungsten as Hydrogen Electrodes in Alkaline Water Electrolysis

Driving force for the formation of Sn whiskers: compressive stress-pathways for its generation and remedies for its elimination and minimization

Multi-purpose finish for printed wiring boards and method of manufacture of such boards

Metallic surface enhancement

Silver plating in electronics manufacture