What is one application of nickel-based catalysts?

Nickel-based catalysts are widely recognized for their role in the hydrogenation of alkenes. This process involves the addition of hydrogen to the carbon-carbon double bonds in alkenes, converting them into alkanes, which are saturated hydrocarbons. The use of nickel as a catalyst in this reaction enhances the rate at which hydrogen is added to these compounds, making the process more efficient and feasible at lower temperatures and pressures compared to non-catalytic methods.

In the context of the other options, photography typically involves different chemical reactions and relies on silver halides rather than nickel catalysts. The production of fertilizers mostly utilizes catalysts that are specific to nitrogen fixation or ammonia synthesis, such as iron or ruthenium-based catalysts, rather than nickel. Water purification often employs different types of filtration and treatment processes that don't revolve around the use of nickel catalysts, focusing instead on biological or physical methods.

Thus, the unique effectiveness of nickel in facilitating the hydrogenation reaction is what qualifies it as a valuable application in the chemical industry.