Can endoergonic reactions happen when energy is supplied? Yes—if energy is supplied from outside. A 2026 Nature Chemistry study gives Class 11 students a modern example: researchers used light, iron salts and a molybdenum catalyst to convert nitrogen toward ammonia in water. The overall process was reported as endoergonic by 329.2 kJ mol−1, so light acted as the energy source that drove the chemistry.
Endoergonic reactions: why energy input matters
An endoergonic process needs a net input of free energy. This is different from saying that the reaction cannot happen. If energy is supplied from outside the system, the transformation may proceed.
In this research, ultraviolet light provides that energy. Iron(II) salts absorb the light and generate solvated electrons, which help reduce a molybdenum catalyst involved in nitrogen reduction.
What the Nature Chemistry study reported
- Light-driven ammonia formation from nitrogen in water.
- Use of inexpensive Fe(II) salts and a molybdenum catalyst.
- About 5.0% photochemical quantum yield at normal temperature and pressure.
- Up to 10.8% quantum yield at elevated nitrogen pressure.
- About 7.6% light-to-chemical energy conversion efficiency.
- An overall process calculated to be endoergonic by 329.2 kJ mol−1.
Research source: Zidouhia et al., “Artificial photosynthetic reduction of nitrogen to ammonia at room temperature using natural seawater,” Nature Chemistry (2026). Source paper.
Thermodynamics versus kinetics
This is an important JEE/CBSE distinction. Thermodynamics tells us whether a process is energetically favourable under the stated conditions. Kinetics tells us how fast it occurs and what pathway it follows.
A catalyst can lower activation energy and provide an alternative pathway, but it does not change the overall energy difference between reactants and products. In this system, the catalyst helps the reaction pathway, while light supplies the required energy.
How this connects to Gibbs energy
At constant temperature and pressure, a positive Gibbs energy change indicates that a process is not spontaneous in the forward direction under those conditions. It can still be driven by coupling to another process or by supplying energy.
For students, the useful reasoning question is: if the process is uphill, where does the energy come from? Here, the answer is light.
CBSE/JEE quick checks
- Can an endoergonic reaction occur? Yes, if sufficient energy is supplied.
- Does a catalyst make ΔG negative? No. It changes the pathway, not the thermodynamic state function difference.
- What is the energy source here? Ultraviolet light.
- Which redox couple appears in the system? Fe(II)/Fe(III).
- Why is this called artificial photosynthesis? Because light energy is used to drive chemical energy storage in a designed system.
Exam-style question
Question: A reaction is endoergonic but occurs under irradiation in a photocatalytic system. Explain why this does not violate thermodynamics.
Answer: The system receives external energy from light. The energy balance therefore includes the radiation absorbed by the reaction system.
Takeaway
Thermodynamically unfavourable does not mean impossible. It means energy must be supplied or the reaction must be coupled appropriately. This research is a strong modern example of a Class 11 thermodynamics idea.
FAQs
Is endoergonic the same as endothermic?
No. Endoergonic refers to free energy, while endothermic refers to enthalpy.
Does the catalyst provide the energy?
No. The light provides energy; the catalyst provides a pathway.
Is this an industrial process already?
The supplied research supports a laboratory-stage photochemical system, not industrial readiness.
For more Chemistry learning resources, explore Topper Formula Chemistry Articles and Topper Formula courses.
Prepared by Lalit Kumar Mishra — Chemistry Educator, Student Success Mentor and Author; Founder of Topper Formula and Creator of The Clarity Blueprint Method™.
Compare thermodynamic and kinetic reasoning with our Haber-process guide to equilibrium and reaction rate. Browse more Chemistry articles.