Exhibit
4.3


 


SPECIMEN
WARRANT CERTIFICATE


 


	NUMBER	 	[    ]
    WARRANTS
	WA-	 	 


 


(THIS
WARRANT WILL BE VOID IF NOT EXERCISED PRIOR TO 5:00 P.M.


NEW
YORK CITY TIME, FIVE YEARS FROM THE CLOSING DATE OF THE COMPANY’S INITIAL BUSINESS COMBINATION)


 


CLEANTECH
ACQUISITION CORP.


 


CUSIP
[_]


 


WARRANT


 


THIS
WARRANT CERTIFIES THAT, for value received                                         ,
or registered assigns, is the registered holder of a Warrant or Warrants (the “Warrant”), expiring on a date which is five
(5) years from the completion of the Company’s initial business combination, to purchase one fully paid and non-assessable share
(the “Warrant Shares”), of common stock, par value $0.0001 per share (the “Common Stock”), of CleanTech Acquisition
Corp., a Delaware corporation (the “Company”), for each Warrant evidenced by this Warrant Certificate. This Warrant Certificate
is subject to and shall be interpreted under the terms and conditions of the Warrant Agreement (as defined below).


 


The
Warrant entitles the holder thereof to purchase from the Company, from time to time, in whole or in part, commencing on the later to
occur of (i) the completion of the Company’s initial business combination or (ii) twelve (12) months following the closing of the
Company’s initial public offering, such number of Warrant Shares at the price of $11.50 per share (the “Warrant Price”),
upon surrender of this Warrant Certificate and payment of the Warrant Price at the office or agency of Continental Stock Transfer &
Trust Company (the “Warrant Agent”), such payment to be made subject to the conditions set forth herein and in the Warrant
Agreement, dated [●], 2021, between the Company and the Warrant Agent (the “Warrant Agreement”). In no event shall
the registered holder(s) of this Warrant be entitled to receive a net-cash settlement in lieu of physical settlement in Warrant Shares
of the Company. The Warrant Agreement provides that, upon the occurrence of certain events, the Warrant Price and the number of Warrant
Shares purchasable hereunder, set forth on the face hereof, may be adjusted, subject to certain conditions. The term Warrant Price as
used in this Warrant Certificate refers to the price per full Warrant Share at which Warrant Shares may be purchased at the time the
Warrant is exercised.


 


This
Warrant will expire on the date first referenced above if it is not exercised prior to such date by the registered holder pursuant to
the terms of the Warrant Agreement or if it is not redeemed by the Company prior to such date.


 



     


     


    

 


No
fractional shares will be issued upon any exercise of a Warrant. If, upon exercise of a Warrant, a holder would be entitled to receive
a fractional interest in a share, the Company will, upon exercise, issue or cause to be issued only the largest whole number of Warrant
Shares issuable on such exercise (and such fraction of a share will be disregarded).


 


Upon
any exercise of the Warrant for less than the total number of full Warrant Shares provided for herein, there shall be issued to the registered
holder(s) hereof or its assignee(s) a new Warrant Certificate covering the number of Warrant Shares for which the Warrant has not been
exercised.


 


Warrant
Certificates, when surrendered at the office or agency of the Warrant Agent by the registered holder(s) hereof in person or by attorney
duly authorized in writing, may be exchanged in the manner and subject to the limitations provided in the Warrant Agreement, but
without payment of any service charge, for another Warrant Certificate or Warrant Certificates of like tenor and evidencing in the aggregate
a like number of Warrants.


 


Upon
due presentment for registration of transfer of the Warrant Certificate at the office or agency of the Warrant Agent, a new Warrant Certificate
or Warrant Certificates of like tenor and evidencing in the aggregate a like number of Warrants shall be issued to the transferee(s)
in exchange for this Warrant Certificate, subject to the limitations provided in the Warrant Agreement, without charge except for any
applicable tax or other governmental charge.


 


The
Company and the Warrant Agent may deem and treat the registered holder(s) as the absolute owner(s) of this Warrant Certificate (notwithstanding
any notation of ownership or other writing hereon made by anyone) for the purpose of any exercise hereof, of any distribution to the
registered holder(s), and for all other purposes, and neither the Company nor the Warrant Agent shall be affected by any notice to the
contrary.


 


This
Warrant does not entitle the registered holder(s) to any of the rights of a stockholder of the Company.


 


After
the Warrant becomes exercisable and prior to its expiration date, the Company reserves the right to call the Warrant at any time, with
a notice of call in writing to the holder(s) of record of the Warrant, giving thirty (30) days’ written notice of such call if
the last reported sale price of the Common Stock has been equal to or greater than $16.50 per share for any twenty (20) trading days
within a thirty (30) trading day period ending on the third (3rd) trading day prior to the date on which notice of such call is given,
provided that (i) a registration statement under the Securities Act of 1933, as amended (the “Act”) with respect to the shares
of Common Stock issuable upon exercise must be effective and a current prospectus must be available for use by the registered holders
hereof or (ii) the Warrants may be exercised on cashless basis as set forth in the Warrant Agreement and such cashless exercise is exempt
from registration under the Act. The call price is $0.01 per Warrant Share. No fractional shares will be issued upon exercise of the
Warrant.


 


If
the foregoing conditions are satisfied and the Company calls the Warrant for redemption, each holder will then be entitled to exercise
his, her or its Warrant prior to the date scheduled for redemption; provided that the Company may require the Registered Holder who desires
to exercise the Warrant, to elect cashless exercise as set forth in the Warrant Agreement, and such Registered Holder must exercise the
Warrants on a cashless basis if the Company so requires. Any Warrant either not exercised or tendered back to the Company by the end
of the date specified in the notice of call shall be canceled on the books of the Company and have no further value except for the $0.01
call price.


 


	By	 	 
	 	Chief
    Executive Officer	 


 




    2


     


    

 


[REVERSE
OF CERTIFICATE]


 


SUBSCRIPTION
FORM


 


To
Be Executed by the Registered Holder(s) in Order to Exercise Warrants


 


The
undersigned hereby irrevocably elects to exercise the right, represented by this Warrant Certificate, to receive shares of Common Stock
in accordance with the terms of this Warrant Certificate and pursuant to the method selected below. Capitalized terms used herein and
not otherwise defined have the respective meanings set forth in the Warrant Certificate. PLEASE CHECK ONE METHOD OF PAYMENT:


 


	 	 	☐	 	a
    “Cash Exercise” with respect to                 
    Warrant Shares; and/or
	 	 	 	 
	 	 	☐	 	a
    “Cashless Exercise” with respect to                 
    Warrant Shares because on the date of this exercise, there is no effective registration statement registering the Warrant Shares,
    or the prospectus contained therein is not available for the resale of the Warrant Shares, in which event the Company shall deliver
    to the registered holder(s)                  shares
    of Common Stock pursuant to Section 3.3.2 of the Warrant Agreement.


 


The
undersigned requests that a certificate for such shares be registered in the name(s) of:


 


	 
	(PLEASE
    TYPE OR PRINT NAME(S) AND ADDRESS)
	 
	 
	 
	 
	 
	 
	(SOCIAL
    SECURITY OR TAX IDENTIFICATION NUMBER(S))


 


	 	 	 
	and be delivered to	 	 
	 	 	(PLEASE
    PRINT OR TYPE NAME(S) AND ADDRESS)


  




     


     


    

 


and,
if such number of Warrants shall not be all the Warrants evidenced by this Warrant Certificate, that a new Warrant Certificate for the
balance of such Warrants be registered in the name of, and delivered to, the registered holder(s) at the address(es) stated below:


 


Dated:


 


	 	 
	(SIGNATURE(S))	 
	 	 
	 	 
	(ADDRESS(ES))	 
	 	 
	 	 
	 	 
	 	 
	(TAX
    IDENTIFICATION NUMBER(S))	 


 




    2


     


    

 


ASSIGNMENT


 


To
Be Executed by the Registered Holder in Order to Assign Warrants


 


For
Value Received,                                     
hereby sell(s), assign(s), and transfer(s) unto


 


	 	 	 
	(PLEASE
    TYPE OR PRINT NAME(S) AND ADDRESS(ES))	 	 
	 	 	 
	 	 	 
	 	 	 
	 	 	 
	 	 	 
	 	 	 


(SOCIAL
SECURITY OR TAX IDENTIFICATION NUMBER(S))


 


	and to be delivered to	 	 	 	 
	 	 	(PLEASE
    PRINT OR TYPE NAME(S) AND ADDRESS(ES))	 	 
	 	 	 
	 	 	 
	 	 	 
	 	 	 


(SOCIAL
SECURITY OR TAX IDENTIFICATION NUMBER(S))


 


of
the Warrants represented by this Warrant Certificate, and hereby irrevocably constitute and appoint                     
Attorney to transfer this Warrant Certificate on the books of the Company, with full power of substitution in the premises.


 


Dated:


 


	 	 
	(SIGNATURE(S))	 


 


NOTICE:
THE SIGNATURE(S) TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT
ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.


 


Signature(s)
Guaranteed:


 


	By	 	 


 


THE
SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS
WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15).