Hydrogen produced by splitting water using electrolysis powered by renewable energy sources such as wind or solar. Green hydrogen produces zero carbon emissions during production, making it the cleanest form of hydrogen. It is seen as critical for decarbonising hard-to-abate sectors like heavy industry, long-haul transport, and ammonia production.

Hydrogen produced from natural gas through steam methane reforming (SMR), the most common and cheapest production method today. Grey hydrogen releases carbon dioxide as a byproduct, accounting for the majority of global hydrogen production. Transitioning from grey to green hydrogen is a key goal of the energy transition.

Hydrogen produced from natural gas with carbon capture and storage (CCS) technology applied to reduce emissions. Blue hydrogen is often positioned as a transitional solution between grey and green hydrogen, offering lower emissions than grey hydrogen while remaining cheaper than green hydrogen at current costs.

A device that uses electricity to split water into hydrogen and oxygen through electrolysis. Electrolyzers are the core technology behind green hydrogen production. The three main types are alkaline, proton exchange membrane (PEM), and solid oxide electrolyzers, each with different efficiency profiles and cost structures.

An electrochemical device that converts hydrogen and oxygen into electricity, producing only water and heat as byproducts. Fuel cells are used in transport (cars, buses, trucks, forklifts), stationary power generation, and backup power systems. Proton exchange membrane (PEM) fuel cells are the most common type for transport applications.

The annual fee charged by an ETF to cover management, administration, and operational costs, expressed as a percentage of assets under management. A lower expense ratio means less drag on returns over time.

The total market value of all investments managed by an ETF. Higher AUM generally indicates greater liquidity, tighter bid-ask spreads, and lower trading costs for investors. AUM fluctuates with market prices and fund inflows or outflows.

As of April 2026, there is one US-listed hydrogen ETF available to investors: the Global X Hydrogen ETF (HYDR). The Defiance Next Gen H2 ETF (HDRO) was closed and liquidated in April 2025, leaving HYDR as the sole dedicated hydrogen ETF on US exchanges.

HYDR tracks the Solactive Global Hydrogen Index, which includes companies involved in hydrogen production, hydrogen fuel cell manufacturing, and hydrogen energy system integration across global markets.

HYDR invests in companies across the hydrogen value chain, including hydrogen producers, fuel cell manufacturers like Bloom Energy and Plug Power, electrolyzer makers like ITM Power, and companies integrating hydrogen into broader energy systems.

The Defiance Next Gen H2 ETF (HDRO) was closed and liquidated in April 2025 due to declining assets and investor interest. The fund had experienced significant losses and its AUM had fallen substantially from its peak, making it uneconomical to operate.

Hydrogen remains a key component of the global energy transition, with governments worldwide committing billions in subsidies and infrastructure spending. However, the sector is still in its early stages and hydrogen stocks have been volatile. Investors should consider their risk tolerance and conduct thorough research before investing. The closure of HDRO in 2025 underscores the niche nature of this space.