What is the Difference Between Photocatalysis and Electrocatalysis

The key difference between photocatalysis and electrocatalysis is that during photocatalysis, catalytic reaction processing is dominated by photoinduced electric carriers, whereas during electrocatalysis, catalytic reaction processing is dominated by external circuit-induced carriers.

Photocatalysis is a photo-activated chemical reaction that occurs when free radical mechanisms are initiated with the contact between the compound and photons having sufficient energy levels. Electrocatalysis, , on the other hand, is a type of heterogeneous catalysis of electrochemical reactions that occurs at the electrode-electrolyte interface.

CONTENTS

1. Overview and Key Difference
2. What is Photocatalysis 
3. What is Electrocatalysis
4. Photocatalysis vs Electrocatalysis in Tabular Form
5. Summary – Photocatalysis vs Electrocatalysis 

What is Photocatalysis?

Photocatalysis is a photo-activated chemical reaction that occurs when free radical mechanisms are initiated with the contact between the compound and photons having sufficient energy levels. It is a type of acceleration reaction of a photoreaction in the presence of a catalyst. In catalyzed photolysis, the light is absorbed by an adsorbed substrate. There is another type known as photogenerated catalysis. It is the photocatalytic activity that depends on the ability of the catalyst to create some electron-hole pairs. These pairs can generate free radicals such as hydroxyl radicals that are able to undergo secondary reactions. The first practical application of this process was the discovery of water electrolysis in the presence of titanium dioxide.

There are two major types of photocatalysis: homogenous and heterogeneous photocatalysis. In homogenous photocatalysis, reactants, and photocatalysts exist in the same phase. The most common examples of this type of reaction include ozone and photo-Fenton systems. In contrast, in heterogeneous photocatalysis, the reactants and the photocatalysts exist in different phases. Some common examples of this type of reaction include mild or total oxidations, dehydrogenations, hydrogen transfer reactions, etc.

What is Electrocatalysis?

Electrocatalysis can be described as heterogeneous catalysis of electrochemical reactions that occurs at the electrode-electrolyte interface. In this process, the roles of both electron donor-acceptor and catalyst are played by the electrode.

An electrocatalyst is a type of catalyst substance that can participate in electrochemical reactions. These substances are specific forms of catalysts that are able to function at the electrode surface. Typically, an electrocatalyst is heterogeneous, e.g. platinized electrode. There are homogenous electrocatalysts as well. These are soluble, and they can assist the transfer of electrons between the electrode and reactants. They can also facilitate an intermediate chemical transformation that we can describe by the overall half-reaction.

What is the Difference Between Photocatalysis and Electrocatalysis?

Photocatalysis is a photo-activated chemical reaction that occurs when free radical mechanisms initiate with the contact between the compound and photons having sufficient energy levels. Electrocatalysis, on the other hand, is a type of heterogeneous catalysis of electrochemical reactions occurring at the electrode-electrolyte interface. The key difference between photocatalysis and electrocatalysis is that catalytic reaction processing in photocatalysis is dominated by photoinduced electric carriers, whereas catalytic reaction processing in electrolysis is dominated by external circuit-induced carriers. Moreover, photocatalysis uses photocatalysts such as zinc oxide, zinc sulfide, cadmium sulfide, and strontium peroxide whereas electrocatalysis uses carbon nanotubes and graphene-based materials, metal-organic frameworks, etc.

The below infographic presents the differences between photocatalysis and electrocatalysis in tabular form for side by side comparison.

Summary – Photocatalysis vs Electrocatalysis

Photocatalysis and electrocatalysis are important analytical processes in chemistry. The key difference between photocatalysis and electrocatalysis is that during photocatalysis, catalytic reaction processing is dominated by photoinduced electric carriers, whereas during electrocatalysis, catalytic reaction processing is dominated by external circuit-induced carriers.

Reference:

1. Vardhan, V. Aditya. “What Is Electrolysis? Definition-Examples.” Adi Chemistry.

Image Courtesy:

1. “Anatase (titania, TiO2) photocatalyst producing hydrogen” By O. Usher (UCL MAPS) (CC BY 3.0) via Commons Wikimedia
2. “Electrocatalyst ANL” By Argonne National Laboratory – originally posted to Flickr as electrocatalystFrom Argonne National Laboratory's Flickr pageUploaded using F2ComButton (CC BY-SA 2.0) via Commons Wikimedia