Yes, an ergonomic chair may effectively lessen sensations of fatigue after work. It does reduce physical strain upon your back, neck, also shoulders. Therefore, your body stays supported and more relaxed all day.
After a full day of sitting the physical stress of poor posture often causes fatigue besides mental exhaustion. Your muscles work harder for keeping you upright when your chair doesn’t support you properly. That is fixed when an ergonomic chair can help you out by doing the heavy lifting instead for your body.
Less strain on your body means more energy left over

When your spine, hips, and shoulders get proper support, poor posture by your muscles isn’t compensated for. That saves energy to prevent soreness causing end-of-day fatigue.
In a chair that is not ergonomic, you might find yourself leaning forward, or twisting, or even slouching just to stay comfortable. Certain muscles are overworked while other muscles weaken. Your lower back and neck show this clearly. Your body feels tired near the time that the workday ends even if you have not moved very much.
With an ergonomic chair your spine stays aligned your arms rest naturally and your legs stay supported. This keeps your muscles both relaxed and balanced. Sitting in such an unsupported position for those hours usually drains energy, and this reduces that.
You stay more focused and less restless throughout the day

An ergonomic chair assists you in experiencing reduced physical discomfort with fewer distractions because it helps your comfort last. That alone results in your improved focus and reduced mental fatigue.
Your brain keeps getting interrupted by way of physical cues when your seat is not comfortable: a sore back, a numb leg, or even a cramping shoulder. This kind of discomfort pulls at your attention from your work and makes tasks feel longer and more exhausting.
Your body must be well supported within. When that is the situation, then those distractions do fade from view. Focus will be yours without shifts stretches or adjustments to yourself always. You use energy better because sustained comfort is useful. Another advantage is the feeling of being less mentally drained at the day's end.
Yes therefore, to switch to an ergonomic chair could make a noticeable difference within how tired you might feel physically and mentally also after what would be a long day of work.