High hopes for hydrogen electrolysers: EPO report looks to the future of green hydrogen production

Hydrogen is often seen as the “fuel of the future” due to its high energy density, its abundance (in water) and clean burning qualities (see our blogs Hydrogen: turning grey to green and Hydrogen: the storage question). The development of hydrogen technologies is particularly important for sustainable aviation – see our blog Aiming for the sky: aviation carbon reduction goals and there is considerable research into developing more efficient ways of storing hydrogen in more convenient forms, for example for use in vehicles (see our blog Meet the material: PowerPaste).

Green hydrogen production involves using renewable electricity to carry out the electrolysis of water (H2O) to give H2 and O2. Currently, only 2% of global hydrogen is green hydrogen, obtained via electrolysis. However, due to a desire to decarbonise the global economy demands for green hydrogen are growing dramatically. In order to meet these growing demands it is estimated that the capacity of water electrolysers needs to be increased from approximately 0.5 GW capacity currently to 350 GW capacity by 2030.

At the same time, there is a requirement to reduce the cost of electrolysers, for example by replacing expensive noble metals with abundant metals and by improving the resistance of electrolysers to degradation.

A recent EPO report, “Innovation trends in electrolysers for hydrogen production” provides an interesting insight into how innovators across the world are rising to meet this challenge.

Overall picture

Water electrolysis is a hot area for innovation with over 10,000 patent families being published in this area between 2005-2020, with an annual increase of 18 % in patent filings year on year during this period. In fact, in 2020 the number of patents relating to water electrolysis was double the number relating to methods of producing grey hydrogen from coal- and oil-based hydrogen sources.

Overall, the highest numbers of patent applications in this area were from China, Japan, South Korea, USA, Germany and France, with Japanese company Toshiba the top applicant overall.

To explore innovation in this area, the EPO have focused on six key sub-technology areas, these are:

  • hydrogen production processes;
  • cell operation conditions and structure;
  • electrocatalyst materials;
  • separators (diaphragms, membranes);
  • stackability of electrolysers (stacks); and
  • photoelectrolysis.

Hydrogen production processes

Between 2005-2020 China had the highest number of patent filings in this area; however, due to their high focus on the domestic market only about 3% of the total number of Chinese patent applications were international (PCT) applications, meaning that 97% of applications made by Chinese entities were Chinese national applications. The top country for international patent filings in this area was the USA, with 2222 applications filed between 2005-2020, followed closely by Japan and Germany. The UK is in eighth position with 288 applications being filed between 2005-2020.

In this section of the report, the EPO compares patent activity in hydrogen production processes using (i) water electrolysis, (ii) solid hydrocarbon fuels, and (iii) liquid hydrocarbon fuels. In 2020, 375 international applications were published relating to water electrolysis, compared to 294 for hydrogen production from liquid hydrocarbons and only 14 for solid hydrocarbons.

The top applicant in the area of hydrogen production was French Industrial gas specialist Air Liquide perhaps unsurprising given their stated commitment to drive the transition to a hydrogen based economy.

Data in the report also suggests that the most important jurisdictions for patent protection were the USA and Japan. However, this might also be skewed by applicants tending to make their first filing in the countries where the invention was first developed.

Cell operation conditions and structure

Electrolysis takes place in the electrochemical cell of the electrolyser, and research is ongoing to increase the efficiency of the cells by varying temperature, pressure and cell structure to make the electrolysis process more cost-effective over a wide range of operating conditions.

Perhaps unsurprisingly, innovation in this area is focused on electrochemical cells operating at ambient temperature and atmospheric pressure, with a total number of 352 and 359 international patents respectively being published in these areas in 2020. A lower absolute number of patents (56) was published in 2020 relating to high pressure cells. However, all of these areas have seen significant increases in the number of patents being published since 2015/2016.

In line with the general trend above, the top patenting countries were Japan, the USA and Germany, with Japanese companies Toshiba, Panasonic and Honda Motor being responsible for ca. 17% of international applications in this area.

Electrocatalyst materials

Traditionally rare metals have been used in the electrodes of electrolysers. However, due to cost and availability considerations it is desirable to decrease the levels of rare metals used in electrolysers. In particular, iridium production is expected to become a bottleneck for the production of electrolysers in the coming years.

Although, technologies using noble metals remain the most popular for patent applications (with 113 patent families published for this technology in 2020), there is also significant interest in using alternative materials, such as non-noble metals, alloys and ceramics (with 57 international patent families published for this area of technology in 2020). Sharp increases in the number of filings in both of these areas have been seen from 2011 onwards, which suggests that these are areas of high interest for electrolyser research.

Diamond electrodes are nitrogen- or boron-doped diamond films formed on a base material such as silicon. These display good chemical stability (potentially increasing the lifetime of the electrolyser) and are able to operate stably in a broad potential window. Although responsible for 48% of the share of international applications from 2005-2020, filings in this area seem to have tailed off recently and the number of published patent applications relating to organic diamond electrodes (and related non-diamond technologies) in 2020 was lower than the number for non-noble metals, alloys and ceramics.

Overall, this suggests that there is significant interest in this area with current research efforts being focused on the development of more efficient rare metal electrodes and electrode which make use of alternative metals.

Separators (diaphragms, membranes)

Separators are important components of electrolysers allowing ionic diffusion between the electrodes whilst preventing the electrodes from touching and the gasses produced at each electrode from mixing.

Overall high levels of activity were seen in the polymer (organic) separator space in the last few years with 420 international applications being published in 2020. Lower, but significant levels of filing were also seen for inorganic (ceramic) separators, with 94 international applications being published in 2020.

Overall, Japan is far in the lead with innovation in this area with 35% of international patent families in this area originating from Japan.

In this area Korean company LG Chem are the top patent filer closely followed by Japanese company Toyota Motor.


A stack multiplies a collection of electrochemical cells connected in series with other components between them, such as spacers and end plates.

The UK was an early innovator in this field being responsible for 11% of filings relating to stack configurations between 2005 and 2011 (second only to the USA). However, since 2015 Japan has taken the lead as the top country for patent applications in this area, with the UK’s contribution to this category tailing off.

It seems that Japan was particularly instrumental in driving filings relating to stack types without bipolar elements.

More recently French and South Korean entities have become more active in this field, with about 34% of all inventions coming from these countries being filed between 2019 and 2020.

However, overall since 2019 the number of new filings in this area seems to have started to decrease. It is postulated that this is due to this field being already well-developed and that the advantages of compactness/space-saving and high space-time yield of this technology have already been optimised.


Water photoelectrolysis involves using sunlight as the energy source to split water in a photoelectrochemical cell.

This area appears to still be in its infancy with the number of patent filings only accounting for about 6.5% of all water electrolysis patents.

The top countries where patents are filed in this area are Japan, the USA and Saudi Arabia. This area appears to be of key interest to Saudi Arabia, who are seeking to transition their economy away from dependence on fossil fuels.

Two distinct types of photoelectrolysis are defined by the EPO, photoelectrode with photoabsorber and electrocatalyst, and photoelectrode with photoelectrocatalysts and with PV power source. Although the USA and Japan are still the top filers in the field of photoelectrode with photoelectrocatalyst, it seems that this is also a key area of focus for the Netherlands, which is in third place for this technology, with most of the patents produced by this country published between 2015 and 2020.

Turning now to photoelectrolysis with a PV power source, it seems that there was a surge of activity in this area between 2015 and 2017. However, the level of activity in this field appears to have dropped off in recent years.

In line with this being a new area of technology 50% of filings were prepared by universities, with two Saudi Arabian Universities: King Fahd University of Petroleum and Minerals and the King Abdullah University of Science and Technology, being in the top 10 applicants.


The EPO’s report provides an excellent overview of developments in the field of electrolysers, a key technology for helping the world reach global net zero targets, particularly in relation to aviation. This report highlights the areas of focus for innovation and identifies the companies and countries leading the way in each of the particular areas of interest.

This report is a useful road map not just for innovators, but also for governments and industry stakeholders looking to explore this area looking whilst striving for net zero.